Northeast Gulf Science Vol. 2, No.2, P. 77-97 December 1978

HYPOTHERMAL MORTALITY IN MARINE FISHESOF SOUTH-CENTRAL FLORIDA

JANUARY, 1977 1

R. Grant GilmoreHarbor Branch Foundation, Inc.

RR I,Box 196Fort Pierce, FL 33450

ever, simultaneous observations of masscold mortality from several regions ofthe state have never been compared indetail. Some differences and similaritiesin low water temperature effects can beseen between both coasts of Floridacompared here. Concurrent observationswere 'made of fish mortality on the Gulfcoast (Sanibel Island and Tampa Bay)and the Atlantic coast (Indian Riverlagoon). All of these areas are shallowcoastal estuaries vulnerable to significantclimatic changes.

Temperate and subtemperate estuarinefishes are generally regarded as eury­thermic when compared to offshorefish populations and subtropical or

77

Frederick H. BerryNatural Marine Fisheries Service

National Oceanic and Atmospheric Administration75 Virginia Beach Drive

Miami, FL 33149

Lewis H. BullockMarine Research Laboratory

Florida Department of Natural Resources100 Eighth Avenue, S.E.St. Petersburg, FL 33701

ABSTRACT: Comparable climatic conditions on both coasts of central Florida resulted in cold in­duced fish mortalities from 19 January to 13 February 1977. Lethal temperatures, the specieskilled and their relative numbers killed are compared for the Indian River lagoon, Tampa Bay andSanibel Island estuarine systems. Fifty-six species were killed in the Indian River area, 36 in theTampa Bay area, while 19 died at Sanibel Island. The higher species mortality in the Indian Riverlagoon may be attributed to local hydrological and topographical conditions-and a richer ichthyo­fauna. Cold-induced mortality was noted in both juvenile and adult tropical fishes. Some tropicalspecies appear to be more eurythermic than others as lethal minimum temperatures ranged from6 to 13 C. Hypothermal stress and mortality were observed in offshore reef fishes.

Prior cold mortality accounts fromthe literature combined with the currentstudy reveal that a total of 132 fisheshave suffered cold mortality in FloridaWaters.

Florida marine fishes variously affect­ed by low seawater temperatures havebeen listed by several authors for specifictimes and locations around the state(Willcox, 1887; Verrill, 1901; Finch,1917; Storey and Gudger, 1936; Storey,1937; Miller, 1940; Galloway, 1941;Gunter and Hall, 1963; Rinckey andSaloman, 1964, Snelson, 1978). How-

1Contribution number lID, Harbor BranchFoundation, Inc., Ft. Pierce, FL.

78 R. G. Gilmore et al.

tropical fishes. However, occasionallyenvironmental extremes may produceextensive mortality in temperate estua­rine fishes (Blegvad, 1929; Gunter,1941, 1945, 1947a, 1947b; Gunterand Hildebrand, 1951; Southward,1958; Moore, 1976). The estuariesexamined in this study are situated, with­in a subtemperate - subtropical transitionzone between the Carolinian and Carib­bean faunal regions (Briggs, 1974). Bothstenothermic tropical Caribbean andeurythermic temperate Carolinian fishesare sympatric within the study areas.In south-central Florida estuaries, thosespecies most sensitive to low tempera­tures are principally tropical species(Storey, 1937; Briggs, 1974). Thesespecies in many cases reach their northernbreeding limits in Florida waters (Briggs,1958, 1974; Robins, 1971; Herrema,1974; Gilmore, 1977) and becomevulnerable to low temperature stress inthis portion of their range (Storey,1937).

Comprehensive water temperature datais lacking in historical accounts of cold­induced fish mortalities in Florida. De­tailed air and water temperature recordstaken during January 1976 and 1977 re­veal atmospheric and water temperaturetrends that may produce hypothermalstress and mortality. It may now bepossible to predict the severity ofatmospheric cold front effects on thelocal fish fauna in the regions studiedbased on combined atmospheric andwater temperature data patterns pre­sented below.

METHODS

Air temperatures and wind conditionsfor the St. Petersburg-Clearwater Airport,Pinellas County, Tampa InternationalAirport, Hillsborough County and the

Vero Beach Airport, Indian River Countywere taken from National Weather Ser­vice (NOAA) records.

Indian River seawater temperatures inthe Vero Beach area were furnished bythe Vero Beach Municipal power plant(in take temperatures). Atlan tic surf tem­peratures at Vero Beach were taken dailyat 0700 hr using a field fahrenheitthermometer. Most seawater ternpej-j.

tures other than those monitored re­motely were taken using a field Celsiusthermometer at a depth of 0.5 to 1.0 mand recorded to the nearest 0.5 C. At­lantic Ocean temperatures at the FloridaPower and Light Hutchinson Islandnuclear power plant were taken 0.75 mbelow the surface on a continuous re­cording Ryan-Peabody thermographapproximately 365 m offshore over awater depth of 6 m. Intake water tem­peratures were also monitored in theTampa Bay area at two electric gen­erating plants, Higgins and Bartow,located on Old Tampa Bay (Fig. 1).The National Weather Service, Ruskin,Florida furnished water temperaturesfor Egmont Key which were taken bythe U. S. Coast Guard. The Florida De­partment of Natural Resources MarineResearch Laboratory furnished Gulf ofMexico bottom water temperatures to j.64 km off Egmont Key on a transect of253°.

Tide information for Mullet Key,Clearwater Beach and Bay AristocratVillage was obtained from the NationalOcean Survey, Rockville, Maryland.

Fishes were collected with dip nets,cast nets, drop nets, seine and gill netsor by hand. When fish collections orservations were made, accurate countsfishes killed were difficult if notpossible in most cases. Therefore,quantitative estimates are based on thesimple and generally accepted abundance

J00

o II 10 18 20

-=-KILOMETERS

10' 30' 80- 00·

+2 .iod

common species present in large num­bers. Quantitative fish samples in theIndian River lagoon were taken withgill nets, seines, and drop nets followingmethods described by Gilmore, et al.(1978).

All nomenclature follows Bailey,et al. (1970) except for the followingrecent taxonomic changes in which the

""GULF0

OF

MEXICO 0.1'3d

nm,.:r.

BREVARD

..::11""/COUNTY

1 .i

+DO

Hypothermal mortality of fishes 79

Figure 1. Florida map: inset 1 = Tampa area; 2 = Indian River lagoon; 3 = Sanibel Island (notenlarged). HBF = Harbor Branch Foundation, Inc. ship channel. FPL and Light Corp., HutchinsonIsland nuclear power plant.

categories of Starck (1968): Rare =

species where three or fewer specimenswere observed or collected; Occasional =

species observed or collected at irregularinteIVals; Frequent = species collectedOn numerous occasions or are taken in alarge percentage of collections; Common=:: species found in virtually every ob­seIVation or collection; Abundant

.4

y

80 R. G. Gilmore et al,

latter name was preferred: Diapterusolisthostomus (Goode and Bean)D. auratus Ranzani (Deckert, 1973);Harengula pensacolae (Goode and Bean)= H. jaguana Poey (Whitehead, 1973);Micropogon undulatus (Linnaeus)Micropogonias undulatus (Linnaeus),Bairdiella chrysura (Lacepede ). = Baird­iella chrysoura (Lacepede) (Choa, 1977).

RESULTS

On 16 and 17 January 1977, anarctic cold front moved over the Floridapeninsula (Fig. 2). A significant drop inair temperature occurred within a re­latively short period of time. Air tempera­tures at 0700 hr on 15 January were 17.2and 20.0 C at the St. Petersburg-Clear­water and Vero Beach airports, res­pectively, but by the 18th, 0700 hr tem­peratures were 2.8 and -1.7 C, res­pectively. On the morning of the 19th alight snow fell over much of Florida andon this and the following three days re­cord low air temperatures occurred overmost of the state (Palm Beach Post,February 1977). During 17~23 Januarystrong NW winds were recorded withaverage velocities of 4.7 m/sec (gusts to18.2 m/sec) and 3.7 m/sec (gusts to 11.3m/sec) for Vero Beach and St. Peters­burg, respectively. Minimum air tem­peratures for the month were observedon the 19th at St. Petersburg (1.7 C)and on the 20th at Ve ro Beach (-3.9 C).Seawater temperatures in the IndianRiver lagoon (27°32.1'N) fell from 16.0C on the 17th to 6.0 C on the 19th. Thedrop in water temperature appeared tofollow the drop in air temperature by24 hours. There was a three day lag bet­ween the minimum air temperature andthe Atlantic water temperature mini­mum, as the Atlantic minimum of 13.6Cwas not reached until the 23rd (27°

~

~~ -,

p ~

Bwa:

~.::> . c ">- ."".> :a: ;; ,

w ~

Go~ ~:IE

w o ~

>- ~ 0

c

1 3 5 7 911 131517 1512' 23 25 21 2; 31

JANUARY 18n

Figure 2. Air and water temperatures ("C) forthe Indian River and Tampa Bay study areas,January 1977. A. Air temperatures are from theVero Beach airport (0-) and the 81. Peters­burg-Clearwater airport (0 - 00 -). B. IndianRiver lagoon water temperatures from the VeraBeach municipal power plant (0_) and the

Harbor Branch Foundation ship channel(0-). Old Tampa Bay water temperaturemeans between the Higgins and Bartow powerplants (6 - - -). C. Nearshore Atlantic Hutchin­son Island water temperatures (~) are plottedwith Egmont Key water temperatures (x _ 0 _).

21.3'N, 365 m from shore). Seawatertemperatures at Egmont Key at themouth of Tampa Bay were considerablylower than Atlantic temperatures (Fig.2). Egmont Key seawater temperaturesremained below 15.6 C from 25 Dec­

ember 1976 until 26 February 1977 whilenearshore Atlantic temperatures did no!fall below 15.6 C until 20 January.Atlantic seawater temperatures were in­fluenced by the proximity of the warmFlorida Current. It is noteworthy that acomparable warm oceanic current doesnot occur adjacent to the Tampa Bayarea. However, inshore waters on bothcoasts had a similar temperature patternalthough the Indian River lagoon reachedlower estuarine water temperatureminima than did Old Tampa Bay. Airtemperatures at Tampa and Vero Beach

Hypothermal mortality of fishes 81

east shore. Because of the cold westerlywinds widespread hypothermal mortalityof mangroves iRhizophora. etc.) occurredonly on the west shore at thislatitude. Lagoon water temperaturesalong the east shore across from theHarbor Branch Foundation Laboratory(27°32'N) fell from 14.5 to 6.0 C within24 hours, 18 to 19 January, while surfacetemperatures along the west shore re­mained above 13.0 C. During thisinitial cooling period a deep ship channel(to 4 m depths) on the west bankapparently acted as a thermal refuge(Fig. 2, Harbor Branch Foundation shipchannel). However, as water tempera­tures dropped to 10 C in this channel onthe 21st, many fishes that had apparentlysought refuge here went into hypother­mal shock and suffered massive hypo­thermal mortality. At this latitudeminimum lagoon seawater temperaturesvaried between 6.0 to 9.0 C until 22January when temperatures rose to10 C. On the 24th water surface temper­atures (1 m depth) had risen to 11 Cwithin the lagoon.

Because of this prevailing westerlywind direction, hypothermal stress andmortality was first observed in the eastside of the lagoon and in mosquito im­poundments where little vegetative coverwas, present and the water was shallow(27

Q32'N).

Fish samples and observationswere first made on 19 January whenjuvenile and small adult Centropomusundecimalis, Mugi] curema, Megalopsatlantica, Diapterus auratus, D. plumieri,Eucinostomus gula and E. argenteus be­gan to show hypothermal stress, primarychill coma (Doudoroff, 1942) and deathnear the east shore of the lagoon. In­dividuals apparently nearing a chill comawere observed swimming erratically nearthe surface, some becoming moribund.On20 January four additional species were

INDIAN RIVER LAGOON

airports were generally lower and not asmoderate as those at the St. Petersburg­Clearwater Airport. The Gulf of Mexico,Boca Ciega Bay and Old Tampa Bay ob­viously influenced air temperatures overpeninsular St. Petersburg. Strong north­westerly winds associated with the coldfront were blowing from the Gulf of

I Mexico, giving St. Petersburg and OldTampa Bay higher temperature mini­mums relative to the other inshore sitesmonitored on both coasts. These samewesterly winds cooled by the Floridaland mass brought relatively coldercoastal temperatures to the Indian Riverlagoon and vicinity.

Hypothermal stress in the local fishfauna was not noticed until 19' Januaryon both coasts. (Snelson, 1978, concurs).Massive mortality, predominately oftropical and subtropical species (Table 1),was observed from 20 to 23 January onboth the Gulf and Atlantic coasts. Thefollowing regional accounts present amore detailed analysis of fish mortalityfor respective areas of Florida.

This shallow saline lagoon (e.g.Salinity range 5 - 55

8

/ _ , mean @ 25°/00)extends 253 km along the east centralFlorida coast from 29°05 'N to 26 8

58'N. The mean depth of the lagoon isapproximately 1.5 m making much ofthe water column vulnerable to atmos­pheric climatic conditions. Much of thelagoon is therefore subject to wind driventidal movements, turbulence, and tem­perature changes.

After the 17 January cold frontmoved over the Florida east coast,

.. Indian River lagoon waters appeared tostratify initially as strong cold westerlyWinds blowing off the mainland cooledand pushed surface waters toward the

82 R. G. Gilmore et 01.

TABLE 1. Fishes killed by low seawater temperatures, 19-24January 1977. Fish abundance cate-gories follow Starck (1968): R= Rare;O = Occasional; F = Frequent;C=Common;A= Abundant.

Other Fla.Indian River Tampa Sanibel Mortality Rec.

Species Lagoon Bay Island 1887 - 1977*

CarcharhinidaeCarcharhinus leucas R 7,9

SphymidaeSphyrna tiburo R 9,11

ClupeidaeHarengula jaguana 0 0 6Opisthonema oglinum 0Sardinella anchovia R

EngraulidaeAnchoa'hepsetus 0

ElopidaeElops saurus 0 F R 4,7,10,11,12Megalops atlantica 0 0 3,4,7,10,11,12

AlbulidaeAlbula vulpes 0 5

OphichthidaeMystriophis intertinctus R 0 6, 10, 11M. mordax 0Bascanichthys teres F

AriidaeArius felis F 0 R 3,7,10,11Bagre marinus 0 A 7,10,11

BatrachoididaeOpsanus beta ROpsanus sp. 0

OgcocephalidaeOgcocephalus radiatus R 11

HemiramphidaeHyporhamphus unifasciatus 0 10,11

BelonidaeStrongylura timucu 0 0

SyngnathidaeHippocampus erectus R 3, 12

CentropomidaeCentropomus pectinatus 0C. undecimalis 0 F 3,4,6,7,8,10,11C. sp. 0

SerranidaeEpinephelus itjara 0 R 3, 10, 11E. morio R 10,11Mycteroperca microlepis 0

RachycentridaeRachycentron canadum R

CarangidaeCaranx hippos C C R ?2, 3, ?5, 6, 7, 10,

11,12Caranx crysos R 3,5,7,10,11Chloroscombrus chrysura 0 RTracninotus carolinus 0 1,7,10,11T. falcatus F 0 C 6, 10, 11Selene vomer C 0 5,6,7

LutjanidaeLu tjanus analis 0 3,5L. griseus 0 0 3,5,7,8,9,10,11L. synagris 0 3,5,6,9, 10,11

GerreidaeDiapterus auratus A 0** 4, 7D. plumieri C C 6,7,8Eucinostomus argenteus C 0 6, 7E. gula C R R 6E. lefroyi 0Gerres cinereus 0 3

Pomadasyidae

..

Hypothermal mortality of fishes 83

Table 1 - (cont.)

Other Fla.

Indian River Tampa Sanibel Mortality Rec.

Species Lagoon Bay Island 1887 - 1977*

Anisostremus virginicus R 3,9

Haemulon parrai F 3,9

H. plumieri R R n, 3,9,10,11

SciaenidaeMicropogonias undulatus R .,

SparidaeLagodon rhomboides R

KyphosidaeKyphosus sectatrix R

EphipidaeChaetodipterus faber 0 F 0 6,10,11

ChaetodontidaePomacanthus arcuatus R 3

Pomacanthus sp. RChaetodon ocellatus R

PomacentridaeEupomacentrus dorsopunicans R

CichlidaeTilapia sp. 0

LabridaeLachnolaimus maximus 0 3

ScaridaeScarus sp. R 3

Sparisoma rubripinne R

MugilidaeMugil cephalus 0 0 ?2, ?4, 10, 11

M. curema C 0 ?2, ?4, 5,7,8,10,11

M. trichodon 0 R ?2, ?3, ?4, 6

M. gaimardianus R

SphyraenidaeSphyraena barracuda 0 2,3,?5,8,9

UranoscopidaeAstroscopus y-graecum R

GobiidaeLophogobius cyprinoides R

AcanthuridaeAcanthurus bahianus RA. chirurgus R

ScombridaeScomberomorus maculatus 0 7,10,11

StromateidaePeprilus burtt R

SoleidaeA chirus fasciatus 0

MonacanthidaeA luterus schoepfi 0 R. R

Monacanthus hispidus F R 3,5,6,7

OstraciidaeLactophrys quadricornis 0 C 0 6,10,11,12

L. trigonus F 3

TetraodontidaeSphoeroides nephelus F 0 R 7

S. spengleri F 3,7,10,11

S. testudineus 0Diodontidae

Chilomycterus schoepfi 0 C R 6,7,10,11

to *Previous mortality records: 1 = Evermann and Bean (1897), 2 = Finch (1917), 3 = Galloway

I (1941), 4 = Gunter and Hall (1963), 5 = Miller (1940), 6 = Rinckey and Saloman (1964),9 =

IStarck and Schroeder (1970), 10 = Storey (1937), 11 = Storey and Gudger (1936), 12 = Willcox(1887). A question marker precedes the author reference number if the correct species is not certain

from the reference.**= New Florida-Gulf coastal record.

84 R. G. Gilmore et al.

seen dead on the east bank of the lagoon,Mugil cephalus, Trachinotus carolinus,Hyporhamphus unifasciatus and Ariusfelis. Large numbers (70+) of tarpon,Megalops atlantica, that were swimmingsluggishly and showing obvious hypo­thermal stress on the 19th, were founddead on the 20th in an east bank im­poundment. In the east bank-mosquitoimpoundment at Jack Island State Park(St. Lucie County), 103 tarpon were re­corded dead, the only additional specieskilled being Diapterus sp. and Mugil sp.(Ranger A. Hoffacker, personal com.)

By 21 January water near the westbank of the lagoon had cooled to 8-10 Cto depths of 4 m in the channels anddeeper portions of the lagoon. Fiftyspecies (Table 1) and thousands of in­dividuals that had apparently soughtrefuge in these deeper waters subse­quently went into hypothermal shock.Many fish continued to die on the 22ndand 23rd of January..On 22 Januaryfishermen dipped hundreds of Trach­inotus carolinus and T. falcata from theHarbor Branch Foundation ship channel.These were in martketable condition,mostly alive but obviously suffering fromhypothermal stress. As the air temper­ature reached its maximum (15 C) onthe 22nd, the pompano were not asreadily caught. From 24 January to 4February bloated carcasses of deadfishes floated to the surface within thelagoon, indicating that many dead fisheshad gone to the bottom and were notaccounted for during the preceding week.As late as 4 February with lagoonseawater temperatures at 14 C, fishes(e.g. mostly Diapterus auratus andCentropomus undecimalis) were ob­served swimming slowly head up at thesurface. Some dead specimens appearedto be relatively fresh. The majority ofthese observations were made in the

Indian River lagoon in St. Lucie, IndianRiver, and Brevard counties as far northas 28°40'N and south to 27°20'N.Concurrent hypothermal fish mortalityobservations were made in the northernportion of the Indian River, BananaRiver and Mosquito lagoons by Snelson(1978).

Previous accounts of extensive hypo­thermal fish mortalities have shown adultdeaths to greatly surpass any juvenilemortality observed (Gunter, 1938, 1941,1947). However, in the Indian Riverlagoon both juveniles and adults of anumber of species died due to hypo­thermal stress, most notably, the mojarrasand Mugil curema. Diapterus auratus ofall sizes were killed in large numbers. Ina finger canal on the east shore of thelagoon (Brevard County, 28°03'N)169 D. plumieri were found dead. Of the144 measured, 40 (28%) were below100 mm in standard length and as smallas 55 mm. Juvenile (i.e. <125 mm SL)Elops saurus, Chaetodipterus faber,Caranx hippos, Bagre marinus, Mugilcurema, Haemulon parrai, Trachinotusfalcata, Lutjanus griseus, L. synagris,L. analis, and Albula vulpes contri­buted from a portion to up to 100%of the mortality, depending on thespecies and location. Only juvenilesof Albula vulpes, Haemulon parrai,Lu tjanus sy nagris and L. analis werekilled. Many juvenile and adult Eucino­stomus gula and E. argenteus werekilled. In many instances adults weremore readily seen and observationsindicated they suffered greater mortalitythan juveniles.

Dead fishes were not seen on theAtlantic beaches until 22 January. Onthis date dead Spartsoma rubripinne,Scarus sp., Diapterus auratus, Hae­mulon plumieri, Anisostremus virginicus,Eupomacentrus dorsopunicans, Poma-

Hypothermal mortality of fishes 85

species were observed to suffer hypo­thermal stress. Differential mortalitywas also seen among four tropicalspecies which commonly occur withinthe study area throughout the year,Strongylura notata, S. timueu, Eupo­maeentrus variabilis and E. dorsopun­ieans. Both S. notata and E. variabilisoccur in higher numbers than theircongeneric species. Hypothermal mortal­ity was only observed in S. timueu andE. dorsopunieans indicating that not onlydo they occur in fewer numbers but theyare possibly more sensitive to hypother­mal stress. Snelson (1978), however,observed only S. notata in the northernportion of the Indian River lagoonsystem where it was "killed or stunnedin small to moderate numbers."

As an extensive ecological survey wasunderway those fishes present in a com­paratively "normal" condition duringthe "cold-kill" period were collectedusing rod and reel, gill, seine and dropnets. Of the species observed killed inTable 1 the following specimens werecollected alive and in "good condition":13 lethargic Diapterus auratus, 50 Eue­inostomus gula, 3oE. argenteus, 1 Elopssaurus leptocephalus and 2421 juvenileMugil eephalus. In addition to these,the following species were collectedand apparently suffered no hypothermalmortality:

AbundantLagodon rhomboidesGobionellus boleosoma

CommonBrevoortia smithiPomatomus saltatrixCynoscion nebulosusC. nothusC. regalisSciaenops oeellataTriehiurus lepturusGobiosoma robustum

canthus sp., Aeanthurus bahianus, andAcanthurus ehirurgus were found on thebeach (Indian River and St. LucieCounties). As most all of these speciesare tropical primary reef forms foundin shallow waters, some hypothermalmortality had apparently occurred onthe inshore Atlantic reef. The minimumwater temperature on these reefs is notknown, but surf temperatures wheresome of the dead reef fishes were beachedreached a minimum of 11.1 C on 23January. Direct observations of reeffishes were not made until the first weekof February when SCUBA dives weremade on shallow Atlantic reef structures(3-7 m depths) within the study area.These observations demonstrated that anumber of reef species survived the coldperiod (e.g. Eupomaeentrus variabilis,Holaeanthus bermudensis, Labrisomusnuehipinnis).

Differential thermal tolerance was de­monstrated by several species of fishesenclosed in an aquaculture pond 1.0 mdeep located at the Harbor BranchFoundation laboratory. The pond con­tained the following fish species on 19January: Cynoseion nebulosus, C. regalis,Pomatomus saltatrix, Traehinotus earol­inus, Centropomus undecimalis, Seom­beromorus maeulatus and Mugil eephalus.The four latter species died when pondtemperatures reached 6 C on 19 January.The three former species survived the en­tire cold period. This observation de­monstrates the differential thermal tol­erances of these species. Similar ob­servations were made of open lagoonfish populations. Cynoscion nebulosus,C. regalis and C. nothus and Pomatomussaltatrix were commonly caught in"good condition" by lagoon sport andcommercial fishermen before the 20thand after the 27th, occasionally betweenthese two dates. None of these latter

86 R. G. Gilmore et 01.

FrequentMenidia peninsulaeSyngnathus scovelli

OccasionalFloridichthys carpioFundulus similisBairdiella chrysouraPogonias chromisSymphurus plagiusa

RareAnguilla rostrataUrophycis floridanusSyngnathus louisianaeArchosargus probatocephalusParalichthys albiguttaFrom the data presented it appears

that lethal thermal minima for thedead fishes observed were between 6.0and 15.0 C. However, observationsmade during the prior year, 1976, tendto indicate the upper minimum in thisrange may be nearer 13.0 C for thetropical fishes that suffered hypothermalmortality in the Indian River lagoon (theupper minimum is probably less than12 C in the Tampa Bay area based onJanuary 1977 observations below). Dur­ing January 1976 (21st - 24th) an inci­dence of hypothermal shock and somemortality was recorded in the IndianRiver lagoon. Surface water temperatureswithin the Harbor Branch Foundationship channel (depth 3-4 m) had gone be­low 15 C on the 19th following a coldfront (0.0 C air temperature minimum)on the 18th. Another cold front passedbetween the 21st and the 22nd and airtemperatures reached 5.0 C on the 23rd.In the ship channel large numbers ofdead Selene vomer, Diapterus auratusand Lutjanus griseus were observed onthe 22nd and 23rd with surface watertemperatures at 13 to 14 C. Some ofthe former species were swimmingerratically at the surface, apparentlypreceding hypothermal shock. Reports

were obtained of Centropomus un­decimalis swimming erratically at thesurface but no mortality was seen inthis species. No fish mortality wasnoted other than in the ship channelalthough other locations within thelagoon were investigated. When com­paring this minor cold kill to the 1977mortality, it appears that some tropicalfishes within the Indian River lagoonwere able to tolerate a "temporary"surface water temperature depressionto 13 C for 24 hours and 14-14.5 C for96-144 hours. Haemulon parrai, Sphy­raena barracuda and Mugil curema, alltropical species, were observed pre­sent and swimming normally withinthe ship channel and were apparentlynot affected to the point of hypo­thermal shock at this location. Shipchannel surface temperatures did notgo below 13 C in 1976 as they did in1977, and air temperatures were not aslow, nor did they stay low for longperiods of time. The cold front passingon 17-18 January 1976 began to lowerchannel water temperatures and thesecond front 72 hours later loweredtemperatures to a lethal 13 C for thethree species killed.

A total of fifty-six fish species sufferedcold mortality within the Indian Riverstudy region, most of which have a trop­ical center of distribution (Briggs, 1958,1974; Robins, 1971; Herrema, 1974;Gilmore, 1977). The most abundantfishes killed in the Indian River lagoonfrom 28°40'N to 27°20 'N were Diapterusauratus, Caranx hippos, Selene vomerand Trachinotus falcatus all of whichhave a Caribbean center of distributionand may be considered tropical.

TAMPA BAY AREA

On 25 December 1976, water tern-

-90 ~"""""''''''''''''TTTTTTTTTTTT''''''''''''''''''''''TrTTTTTTTTTT''''''''''rTT"'nTT'''''''''''TTTTTT"nTT'TT'lTT1"TTT'1

Figure 3. A. Wind direction and velocity (knots) recorded at St. Petersburg-Clearwater Airport,18-20 January. 1977. B. Difference between actual and predicted tides at three tide stations in theTampa Bay area, 18-20 January 1977.

20T H

CLEARWATER BEACH c>-----OMULLET KEY ...._.-.

BAY ARISTOCRAT .---...

19TH

JANUARY 1977

Hypothermal mortality of fishes 87

ed by three Tampa Bay area electricpower plants reached a minimum 12-16hours after the coldest air temperature(0 C) was recorded.

At 1900 hours EST on 19 January1977, several dead Trachinotus falcatusand Diap terus auratus were observedalong St. Petersburg Beach where thesurf water temperature was 8.1 C. Thesemortalities indicated that inshore watershad already reached lethal thermalthresholds for some fish species. TheseD. auratus specimens were the first re-

N

18TH

gusts~III

HOURS

o

-60

-30

+30

o

10

30

40

DIFFERENCEBETWEEN ACTUALAND PREDICTEDTIDES (em)AT THREE TIDE

STATIONS IN THETAMPA BAYAREA

WIND DIRECTIONAND VELOCITY(KNOTS)ST PETERSBURG.- 20

CLEARWATER

AIRPORT

peratures monitored by the U. S. CoastGuard at Egmont Key fell below 15.6 Cand remained so until 26 February1977.

Figure 2 summarizes physical condi­tions during passage of the arctic coldfront through the Tampa Bay area on17-23 January. Wind velocities fluctuatedbut remained from 310-350° direction(Fig. 3). Tidal levels were less than pre­dicted due to strong winds, allowingshallow bay waters to become wind mixedand chilled. Water temperature monitor-

88 R. G. Gilmore et al.

cords for this tropical species from theFlorida Gulf coast.

Additional observations on 19 Januaryat McKay Creek, a tidal stream flowinginto the southern reaches of ClearwaterHarbor, provided only one recordedmortality, Hippocampus erec tus. How­ever, six other species were experiencinghypothermal stress at water temperaturesranging from 6.7 to 7.7 C.Mugil curema,Diapterus plumieri, Harengula jaguana,and Eucinostomus argenteus were lyingon their sides or belly-up and exhibitedfeeble swimming attempts only whenprobed. Other M. curema and a single

Centropomus undecimalis (885 mm TL)were observed swimming slowly nearthe surface. Disoriented Caranx hipposswam in circles with their heads breakingthe water surface similar to behaviordescribed for centropomids and gerreidsin the Indian River lagoon. These specieswere apparently approaching primarychill coma and were found dead by fish­ermen the following morning.

From 0230 to 0330 hours on 20January, water temperatures in BocaCiega Bay at Pinellas Bayway rangedfrom a near surface reading of 6.6 C(15 em depth) to 9.2 C (3-4 m depth).Dead fishes included two Lactophrysquadricornis and a single Kyphosussectatrix. Individual specimens of Cent­ropomus undecimalis (975 mm TL) anda L. quadricomis were alive but strandedin shallow water.

Dead Elops saurus were observed on21 January at Memorial Causeway inClearwater (1404 specimens/Lf km)where the water temperature was 10.5 C.In contrast, on 23 January this speciesappeared unstressed in Spring Bayou inTarpon Springs where the water tempera­ture was 15.3 C. The higher water tem­perature in Spring Bayou is due to a re­latively warm freshwater spring discharge

(Wetterhall 1965) which provides a ther­mal refuge for these fish.

On 26 January water temperaturesranged from 12.8 to 13.0 C in McKayCreek, Boca Ciega Bay (Maximo Moor­ings) and lower Tampa Bay (WhistlerYacht Basin). Mugil sp. (approx. 200mm TL), Tilapia sp. and Diapterusplumieri swam lethargically near sea­walls. Disoriented Mugil sp., Elopssaurus and Caranx hippos swamerratically at the surface and occasion­ally collided with pilings or seawalls.Wounds, presumably caused by mech­anical abrasion, were evident on thesefishes.

Air temperature fell to 3.3 C atAlbert Whitted Airport in St. Peters­burg on 30 January; Tampa Bay waterswere sufficiently chilled to cause furthermass mortalities in Mugil spp., Lacto­phrys quadricornis, Centropomus un­decimalis and Chilomycterus schoepfiat Mullet Key.

Predation as a secondary effect ofhypothermal stress most likely plays asignificant role in the total number offish mortalities. Moss (1973) noted pre­dation by double-crested cormorants,Phalacrocorax auritus, on Monacanthushispidus and Aluterus schoepji duringperiods of low temperature in a NewEngland estuary. A similar incidentoccurred in St. Petersburg at FrenchmanCreek on 23 January where a double­crested cormorant was observed eatingsmall Mugil sp. too lethargic to evadecapture. On another occasion a singleCentropomus undecimalis was noted toconsume a mojarra experiencing equil­ibrium problems.

Storey (1937) stated that C. un­decimalis was consistently harmed byfreezes at Sanibel Island, Florida; Mar­shall (1958) also noted their vulner­ability to cold. However, during January

'0. .0. 2~. 'h ,.. ..., , I I.... il.p,. ~

~ 20

lU ..Q;:::> I.t(Q;

17~~

"lU....Q; '"lU

~ 14~

1~5~0.... IZ....0

11III

10 .._- --•• •a .. •• II a

Stal 510_2 .... .... .... ....DISTANCE OFF EGMONT KEY

(KILOMETERS)

Figure 4- Gulf of Mexico bottom water tem-peratures to 64 km off ElJROnt Key on atransect of 253°.

rruruma on 25 January (11.6-12.7 C).Further offshore, 48 to 64 km, 30-40m depths, bottom water temperaturesreached temperature minima on 15February (13.0-13.6 C). During a SCUBAdive on 13 February made on offshoreledges 18.3 m deep (27°29'N, 83°01'W)decomposing remains of several Lutjanusgriseus were found. Live individuals ofL. griseus and Lachnolaimus maximusshowed evidence of lateral scale loss anderoded fins. Similar conditions werenoted for these same species inhabitingledges 39.6 m deep (27°24'N, 83°22'W).This latter observation tends to indicatethat even offshore reef fishes at depthsof 39 m were not protected from hypo­thermal stress in the Gulf of Mexicoduring February 1977. Scale loss wasevident on these same species at thesereefs until June. An attempt to isolateopportunistic pathogens from an affectedL. griseus was unsuccessful; a necropsyrevealed no internal pathological mani­festations. Scale loss and eroded finswere initially assumed to be a result ofbuffeting of Lutjanus griseus and Lach­nolaimus maximus against limestone

Hypothermal mortality of fishes 89

lethargic C. undecimalis that had notcompletely succumbed to low tem­peratures, were highly visible near sea­walls. Capture employing cast nets,snatchhooks and spears was common inboth the Tampa Bay and Indian Riverareas.

In the Tampa Bay area C. undecimalis,Caranx hippos, Megalops atlantica, Elopssaurus, Mugil sp. and Diapterus plumieriwere observed to crowd into shallowwater in marinas and tidal creeks. In theupper reaches of McKay Creek, wherewater depth at high tide does not exceed1 m, unusually large numbers of Caranxhippos and Diap terus plumieri were dis­covered during the coldest periods ofJanuary. Observations in the Tampa Bayarea seem to indicate that protectedmarinas, as well as spring fed tidal creeks,served as shallow water refuges, possiblysubject to solar warming.

A total of thirty-six fish species suffer­ed cold mortality in the Tampa Bay studyarea during January 1977. Of the 16 fishspecies recorded as affected by low watertemperatures in Tampa Bay during 1962(Rinckey and Saloman 1964), only fourspecies were not observed in the presentstudy: Lutjanus synagris, Synodus foe­tens, Microgobius gulosus, Diodon sp.The dominant fishes killed in 1962 and1977 were Caranx hippos and Diapterusplumieri.

Underwater observations of fishesassociated with offshore reef formationswere made from 13 February to 30 June,immediately following the described in­shore fish mortalities. Surface andbottom seawater temperatures in theGulf of Mexico were taken during twohydrographic transects made on 25January and 15 February up to 64 kmdue west of Egmont Key (Fig. 4).Bottom waters 8-32 km offshore in10-25 m depths reached temperature

90 R. G. Gilmore et 01.

SANIBEL ISLAND

g(t

~

r

f

I

Stenothermic tropical and subtropicalfishes suffered the greatest mortalityduring January 1977. These species werealmost entirely typical estuarine and

Sanibel Island at 1030 EST,January 20.Hundreds of Bagre marinus and severalTrachinotus falcatus were dead along thetwo fill areas of the causeway. Observa­tions and collections of representativedead fishes were made along the causewayon the afternoon of January 20 and themorning of January 21 and along thesouthern Gulf beach on the afternoon ofJanuary 21. Nineteen fish species wererecorded during the period: ca. 5,000to 10,000 Bagre marinus, 47 Tracht­notus falcatus, five species with two toseven individuals each, and 12 speciesrepresented by a single specimen each(Table 1). In addition, dead Centropomussp. were reported in some island canals.

Three of the 47 Trachinotus falcatusrecorded were the only fish living andshowing hypothermal stress seen in thesurvey. These were slowly and erraticallyswimming in the surf during January 20and 21. Some stressed Centropomus sp.were reported from some canals.

Several unexpected occurrences andaspects were noted for the dead speciesobserved. A size-selected sample ofBagre marinus ranged 256 to 455 mm FL(fork length) and 228 to 1650 gmRD (round weight) while the singleArius felis was 220 mm FL and 127 RD.The size range of Trachinotus falcatuswas appreciable, ranging from 160 to462 mm FL and 107 to 2142 gm RD.Only two specimens of Mugil werefound and these were within a 25 meterdistance on the causeway and weredifferent species (Mugil trichodon 262mm FL and 210 gm,MugU gaimardianus305 mm FL and 440 gm).

DISCUSSION11.110.612.813.6

recorded on

Sanibel Island west of Ft. Myers,Florida, is bordered by the Gulf ofMexico to the west and south and byPine Island Sound to the northeast andSan Carlos Bay to the southeast. It isconnected to the mainland by a three­bridge causeway (4.5 km long) with twomajor fill areas (total 2 km). Observationsrelated to this report were from ca.26"25' - 29'N, 82°02'W.

Four paired temperature records weremade with a handheld thermometer:Date EST Air °c Surf °c---Jan. 21 0720 12.2Jan. 22 0830 8.3Jan. 22 0930 12.2Jan. 22 1300 14.4

Fish mortality was first

ledges as they attempted to maintain inturbulent waters. However, similar condi­tions were observed in these fishes at adepth of 39.6 m where turbulence wouldpresumably be insignificant. During Feb­ruary and early March Mycteropercamicrolepis and Epinephelus moria werefound under deeply undercut ledges.Lethargic individuals of Balistes cap­riscus and Haemulon plumieri could beremoved from their hiding places byhand. Species appearing relatively activeduring the cold included: Serranussubligarius, Centropristis sp., Diplectrumformosum, Halichoeres bivittatus andothers.

The total number of offshore speciesof fish adversely affected is unknown.However, the chance sighting of deadPomacanthus arcuatus and Chaetodonocellatus floating at the surface 28 kmSW of Egmont Key on 23 January(G. B. Smith, personal com.) indicatesthat more species were killed thanthose listed here.

[

shallow coastal zone inhabitants. Thosespecies killed that belong to large, widelydistributed neritic families (predomi­nantly found offshore) with speciesoccurring throughout both tropical andtemperate regions were either inshorerepresentatives of their family (e.g.Carcharhinus leucas and Hyporhamphusunifasciatuss and/or stenothermic re­presentatives of their family (e.g. Har­engula jaguana).

A combination of physical conditionsproduced the extensive fish mortalityobserved in the study areas: 1) thepassage of the cold front was sudden,2) water temperature minima werevery low (to 6.0 C) and 3) water tem­peratures remained low (6.0 - 12.0 C)for five to six days. Deeper water withinthe estuaries was not an adequate havenas high northwesterly winds associatedwith the Arctic front caused extensivewater turnover and an adequate pro­tective thermocline did not develop.Subsequently, the entire water columnto depths of 4 m cooled within 48hours to 72 hours, producing extensivemortality in these potential refuges. Asimilar deep water "refuge-death trap"phenomenon has been noted by otherauthors (Tabb 1966; Moore 1976;Snelson 1978). Lower than averagetides partially induced by strong north­westerly winds increased the severity ofthermal conditions in the Tampa Bayarea. In some cases, shallow protectedwaters and creeks fed by thermal springs(e.g. Spring Bayou, Tarpon Springs) didnot cool to lethal temperatures and somefishes were able to live through the coldperiod in these areas.

Fishes with limited mobility weregreatly affected. Plectognath fishes(puffers, Tetraodontidae and Diodon­tidae; boxfishes, Ostraciidae; file fishes,Monacanthidae; and triggerfishes, Balist-

Hypothermal mortality of fishes 91

idae) are notable for their tropicalaffinity, poor mobility and high occur­rence in hypothermal fish kills. Theycould not escape the rapidly coolingshallow waters as readily as other species,and subsequently their bodies werecommonly found along lagoon beaches.

Many cryptic and diminutive tropicalblennies and gobies were probably alsokilled but were not as readily observed.Of these latter two families only twogobies, Lophogobius cyprinoides andMicrogobious gulosus, have been ob­served in winter mortalities (Rinckeyand Saloman 1964). Adequate ob­servations of very small species (adults25 mm or less SL) and larvae «20 mm)of larger species have yet to be made.

Most observations made by Storey(1937) are in agreement with our find­ings. However, her placement of thepompano, Trachinotus carolinus andSpanish mackerel, Scomberomorus ma­culatus on the "seldom hurt" list doesnot agree with observations made in theIndian River lagoon. Both species arewell known for their narrow thermallimits (Berry and Iversen 1966; Klima1959) and have suffered hypothermalmortality along the Florida east coast(Evermann and Bean 1897; Snelson1978). Since cold mortality in thesespecies was only noted within the con­fines of the Indian River lagoon, it ispossible that these mobile species werenot able- to make it to the nearest oceanaccess before they suffered hypothermalstress and subsequently lapsed into aprimary chill coma. Ready access towarmer Atlantic Ocean or Gulf watersmay prevent mortality in T. carolinusand S. maculatus in other areas ofFlorida.

January 1977 temperature data indi­cate that seawater temperatures weregenerally lower in Gulf coastal areas of

TABLE 2 . Sample of tropical fishes commonlyoccurring in shallow coastal waters of theIndian River study area bu t not recorded fromthe Tampa Bay area.

Bay area may be able to escape coldertemperatures more readily than thosein the Indian River lagoon. They may alsobe better conditioned to cold tempera­ture response as seasonal water tempera­tures decrease earlier and apparentlymore gradually than on the central eastcoast (Fig. 2). These coastal differencesin temperature regimes may account forthe absence of a number of tropicalspecies from the Tampa Bay area, whichare not uncommon in the Indian Riverregion (Table 2). Table 2 is a partial listof the tropical species not shared byboth study areas and only the morecommon forms of the Indian Riverlagoon system are listed (Gilmore1977). A number of these fishes occurin the northern Gulf along the Florida

killed

killed

killed

killed

killed

killed

killed?

killed

killed

OBSERVED COLDEFFECT. 1977

frequentcommon

frequent

commoncommon

abundant

ABUNDANCESPECIES

ScorpaenidaeScorpaena plumieri

CentropomidaeCentropomus pectinatus

ApogonidaeApogon macula/us

CarangidaeCaranx ruber

LutjanidaeLutjanus analisL. jocu

GerreidaeEuctnostomus lefroyt

PomadasyidacAntsostremus sunnamensisHaemulon parmi

SciaenidaeBairdiella sanctaetuctaeUmbrina corotaes

PomacentridaeEupomacentrus dorsopunicans

LabridaeHalichoeres maculipinnaThalassoma btfasctatum

ScaridaeSparisoma cnrysopterumS. rubripinne

ClinidaeLabnsomus nuchipinnisMalacoctenus triangulatus

BlenniidaeBlenniuscrtstatusHypluerochilus bermudensts

GobiidaeCoryphopterw dicrusGobionelius smaraedusG. stigmaturusLophogobius cyprmotaes

AcanthuridaeAcanthurus chirurgus

BcthidaeCitharichthys spuopterus

TetraodontidaeSphoeroides testudineus

the same latitude than they were on theAtlantic coast (Fig. 2). Arctic coldfronts coming from the northwest,shallower offshore Gulf waters, and theFlorida Current along the Atlantic coastcan help explain this neritic water tem­perature phenomenon. Yet inshore est­uarine waters had a similar trend onboth coasts, with Indian River lagoonwater revealing a lower minimum due tostrong westerly winds cooled further bythe Florida land mass.

Fewer fishes were observed to suffermortality in the Tampa Bay area than inthe Indian River lagoon (36 versus 56).Fewer fish species occur in the Tampa Bayarea (27°00 '-28°00 'N, 82°25'-84°30'W),(approximately 370 species, Springer andWoodburn 1960; Moe and Martin1964: Powell et al. 1972: Smith 1976)than in the Indian River area (664 species,Gilmore 1977, and unpublished data).Those tropical and eurythermic tropicalspecies that do occur in the Tampa Bayarea appear to make a seasonal migrationoffshore during the colder winter months(Springer and Woodburn ibid). In theIndian River lagoon many tropical formsappear to remain within the lagoon al­though in fewer numbers as indicated bywinter seine captures (Gilmore et al.1975, 1976, unpublished Harbor BranchFoundation Annual Report) and therecent fish kill. The topography of theTampa Bay area permits ready accessfrom inshore bays to the Gulf of Mexico,and this access is apparently utilized bymany stenothermic warm water speciesin their annual offshore migration ascoastal waters cool (Springer and Wood­burn 1960). For 253 km along theFlorida central east coast there areonly five small inlets that continuallygive access to the open Atlantic Oceanfrom the Indian River lagoon system.Warm stenothermic fishes in the Tampa

92 R. G. Gilmore et at.

has indicated that juvenile fishes maywithstand lower water temperature thanadults of the same species. This may betrue on the Texas coast as many juvenilesciaenids, atherinids, etc. (subtemperate­Carolinian fauna) may be found inshallow coastal waters during the coldermonths of the year (Gunter, 1945;Gallaway and Strawn, 1974). However,the southern half of the Indian Riverlagoon has a depauperate sciaenidpopulation (excluding Cynoscion nebul­osus and Bairdiella chrysoura whichspawn during the warmer months) andthere is no large influx of juvenilesciaenids (e.g., Micropogonias undulatusand Leiostomus xanthurus) during thewinter-early spring comparable with thatseen along the Texas coast (Gunter,1945; Gallaway and Strawn, 1974).Two notable exceptions to the juvenilecold mortality were observed in themonthly seine catch within the IndianRiver during January, 1977. Largenumbers of juvenile (10-25 mm SL)Mugil cephalus, which has a circumtrop­ical-warm temperate distribution (Moore,1976), and Lagodon rhomboides, pre­dominately a warm temperate Carol­iman species (Caldwell, 1957), werecaptured in active schools at tem­peratures as low as 10.0 C during andafter the observed period of maximumcold mortality. However, adult Mugilcephalus did die during the period ofmaximum cold mortality. Although nojuvenile croaker, Micropogonias un­dulatus, were seen, several adults ofthis species were found dead at two

lagoon stations. These data suggest thatstenothermic tropical and subtropicalfishes are cold sensitive at all stages ofdevelopment while subtemperate Carol­inian forms are relatively eurythermicas juveniles. Subtemperate Carolinianadults are somewhat less eurythermic

Hypothermal morality of fishes 93

coast (Hastings, 1972; G. Smith, 1974;Walls, 1975) primarily during the warmermonths as juveniles and in some cases asadults also. It should also be noted thatuntil this study, Diap terus auratus, whichis common to abundant in the IndianRiver lagoon, suffering the highesthypothermal mortality, was not recordedfrom the Florida west coast.

Fewer species were seen in the hypo­thermal mortality at Sanibel Island thanin the other study areas. Other observersin the Sanibel Island area also indicated arelatively low mortality occurred (T. H.Fraser, Environmental Quality Lab.;Fla. Marine Patrol, personal com.). Theminimum recorded surf temperature was10.6 C on 22 January, two to three de­grees higher than minimums on the sameday at Tampa Bay and the Indian Riverlagoon. Besides having higher water tem­peratures, the Sanibel study area was at alocation accessable to the more moderateopen waters of the Gulf of Mexico. Theseobservations indicate that the SanibelIsland area did not have as severe morta­lity as the Tampa Bay area and IndianRiver areas.

Unpublished data on spawning periodsand seasonal juvenile abundance withinthe Indian River lagoon indicate thatjuveniles of many species are not commonor present during the colder wintermonths (Gilmore, et al., 1976, un­published Harbor Branch FoundationAnnual Report). However, there are afew tropical species that are present asjuveniles during the winter (e.g. Dia­pterus auratus, Haemulon parrai, etc.).Because large numbers of juveniles andadults of a number of these tropicalspecies (e.g. D. auratus, E. saurus, H.parrai) suffered hypothermal mortality itcan be assumed that tropical species aretemperature sensitive at most stages ofdevelopment. Gunter (1938,1941,1947)

TABLE 3. Fishes previously recorded as killed by cold in Florida but not recordedby the authors <turing the January 1977 freeze. Author code numbers follow Table 1with one addition: 13::: Tabb, 1958.

94 R. G. Gilmore et al.

than their juveniles and are capable ofmaking extensive migrations to warmerwater (Gunter, 1945; Springer and Wood­bum, 1960).

Variable hypothermal mortality oftropical fishes in the Indian Riverlagoon in both January 1976 and 1977demonstrates differential low' lethaltemperatures in these fishes. Observedlethal temperatures ranged from 6 to13 C. Diapterus auratus, Selene vomerand Strongylura timucu, etc. wereobserved dead at the upper end of thelethal temperature range while Strong­ylura notata, Haemulon parrai andCentropomus undecimalis, etc. diednearer the low end of the observedlethal temperature range. This diff­erential death of tropical fishes over arange of lethal temperatures has alsobeen observed by Graham (1971, 1972)in controlled laboratory experiments.His lower lethal temperature range was8-13 C using various tropical speciesfrom Panamanian waters. These ob­servations demonstrate that some trop­ical fishes are more eurythermic thanothers.

In addition to the 77 species affectedby cold in January 1977, 55 otherfishes have been recorded in previouspublications as suffering mortality duringperiods of extreme cold in Florida(Table 3). Therefore, a total of 132 fishspecies have suffered cold mortality inFlorida waters. The vast majority ofthese fishes are tropical and subtropicalspecies. If more extensive observationswere made of hypothermal mortalityin shallow water reef fishes, the com­prehensive mortality list for Floridawaters would undoubtedly be longer.

ACKNOWLEDGEMENTS

We would like to thank Eustice

SPECIES'

CarcharhinidaeCarcharmnus sp.Rhizoprionodon terraenovae

SphymidaeSphyma (zygaena)?

ClupeidaeBrevoortta smith;

Synodon tidaesvnoaus [oetens

BatrachoididaeOpsanus tau

AntennariidaeAntennanus ocelkuus

HemiramphidaeChriodorus atherinoidesHemiramphus brasiliensis

BelonidaeStrongv/ura notateTvtosouruscrocodtJus

SerranidaeEpinephelus strtatusDtptectrum formosumMycteroperca bonact

PomatomidaePomatomus saltatrix

EcheneidaeEcheneis naucTates

CarangidaeOligoplites saurwSeriola sp.Caranx latus

LutjanidaeLutianus apodusL. jocuOcyurus cnrysurus

PomadasyidaeHaemulon oorraiH aurolineatumH j1avolineatumH macrostomumH striatumOrthopristis chrysoptera

SparidaeArchosargus probatocepnatusA. rhomboidalisCalamus sp.Lagodon rhomboides

SciaenidaeBairdiella chrysura

Cvnoscion nebutosusEquetus acuminatusLeiostomus xanthurusMenticirrhus sp.Sctoenops ocettata

PomacanthidaeHolacanthus bermudensisH ciliarts

PomacenmdaeAbude/dufsaxatilis

ScaridaeNtchclstna ustaScarus guacamaiaS coeruteusSparisoma (chrysopterum or rubripinne)

GobiidaeMicrogobius eutosus

Acan thuridaeAcanmurus coeruleus

TrichiuridaeTrichiurus lepturus

ScorpaenidaeScorpaena sp.

BothidaeSyacium mtcrurum

BalistidaeBatistes capnscusMonacanrhus ciliatus

Ostraciidaeloctophrys btcauaahs

Diodon ndaeChilomycterus atingaDtodon hvstrtxDiodon sp.

Total: 55 species* = fish that may have been killed by fishermen.

AUTHOR

II11

II

7'

6,10,11

10,11

7,10,113

33

3,10,11

II

7,11,10 (possiblyE. neucratoiaesi

10,1110, II

8

3,99

3,9

33333

10,11

1l,1255

7,9,11

77*,11,12,13

37II

11,12

333

3 (asS ftavescensv

7'

10,113

Hypothermal mortality of fishes 95

Briggs, J. C. 1958. A list of Floridafishes and their distribution. Bull.Fla. St. Mus., 2(8): p. 224-319.

1974. Marine zoogeo­graphy. McGraw Hill Book Co.475 p.

Caldwell, D. K. 1957. The biologyand systematics of the pinfish, Lago­don rhomboides (Linnaeus). Bull.Fla. St. Mus., 2(6): 77-173.

Chao, L. N. and J. A. Musick. 1977.Life history, feeding habits, andfunctional morphology of juvenilesciaenid fishes in the York Riverestuary, Virginia. Fish. Bull. 75 (4):657-702.

Christensen, R. F. 1965. An ichthyo­logical survey of Jupiter Inlet andLoxahatchee River, Florida. Unpubl.M. S. Thesis, Fla. St. Univ., Talla­hassee. 318 p.

Deckert, G. D. 1973. A systematic re­vision of the genera Diapterus andEugerres: with the description of anew genus, Schizop terus (Pisces:Gerreidae). Unpubl. M. S. Thesis,Northern Illinois Univ. Dekalb: 74 p.

Doudoroff, P. 1942. The resistance andacclimatization of marine fishes totemperature changes. 1. Experimentswith Girella nigricans (Ayres). Biol,Bull., 83(2): 219-244.

Evermann, B. W. and B. A. Bean. 1897.Indian River and its fishes. In: Reporton the fisheries of the Indian River.J. J. Brice, Senate Document No. 46:40 p. 36 pl.

Finch, R. H. 1917. Fish killed by coldwave on February 2-4, 1917, inFlorida. Mon. Weather Rev. 4-5:171-172.

Gallaway, B. J. and K. Strawn. 1974.Seasonal abundance and distributionof marine fishes at a hot-water dis­charge in Galveston Bay, TexasContrib. Mar. Sci. 18:71-137.

Bailey, R. M., et al. 1970. A list ofcommon and scientific names offishes' from the United States andCanada. 3rd ed. Am. Fish. Soc.Spec. Publ. No.6: 150 p.

Berry, F. and E. S. Iverson. 1966. Pom­pano: Biology, fisheries and farm­ing potential. Proc. Gulf and Carib.Fish. Inst., 19th ann. Sess.: 116-128.

Blegvad, H. 1929. Mortality amonganimals of the littoral region in icewinters. Rept. Danish Biol, Sta., 35:49-62.

LITERATURE CITED

Parnelle and Ross Wilcox of the FloridaPower and Light Corporation for pro­viding water temperatures from plantsin the Tampa Bay and Indian River studyareas, respectively. Mr. Shuler Masseykindly provided water temperature datafrom the Vera Beach municipal powerplant. Mr. Charles Gollnick of the VeroBeach Recreation Department kindlyprovided Vero Beach surf temperatures.George Kulczycki, Phil Hastings, JonDodrill, David Mook and Coddy Williamstook water temperature data and relatedvaluable observations from the IndianRiver lagoon. Brian Barnett of theFlorida Game and Freshwater FishCommission and Ranger Allen Hoffackerof the Florida Department of NaturalResources both provided invaluablecomments and observations on fishkills in Indian River and St. Luciecounties, respectively. We would liketo thank George Henderson, DannieHensley, Mark Leiby, James Seagle,Gregory Smith all of the Florida De­partment of Natural Resources MarineResearch Laboratory, St. Petersburgand Robert Jones of the Harbor BranchFoundation for their constructive com­ments on the manuscript.

96 R. G. Gilmore et al,

Galloway, J. C. 1941. Lethal effect ofthe cold winter of 1939-40 on marinefishes at Key West, Florida. Copeia,1941 (2): 118-119.

Gilmore, R. G. 1977. Fishes oftheIndianRiver lagoon and adjacent waters,Florida. Bull. Fla. St. Mus. 22(3):101-147.

- et al. 1978..Portabletripod drop net for estuarine fishstudies. Fish. Bull. 76(1):285-289.

Graham, J. B. 1971. Temperaturetolerances of some closely relatedtropical Atlantic and Pacific fishspecies. Science 172 :861-863.

-----. 1972. Low-temperatureacclimation and the seasonal tem­perature sensitivity of some tropicalmarine fishes. Phys. Zool. 45(1):1-13.

Gunter, G. 1941. Death of fishes due tocold on the Texas coast,January 1940.Ecology 22: 203-208.

-----. 1945. Studies on marinefishes of Texas. Pub. Inst. Mar. Sci.,1(1): 1-190.

-----. 1947a. Differential rate ofdeath for large and small fishescaused by hard cold waves. Science106: 472.

1947b. Catastrophism inthe sea and its paleontological signi­ficance, with special reference to theGulf of Mexico. Am. Jour. Sci.245(11): 699-776.

and G. E. Hall. 1963.Biological investigations of the St.Lucie estuary (Florida) in connectionwith Lake Okeechobee dischargesthrough the St. Lucie Canal. Gulf Res.Rept., 1(5): 189-307.

--__ and H. H. Hildebrand. 1951.Destruction 0 f fishes and otherorganisms on the sou th Texas coast bythe cold wave of January 28-February3,1951. Ecology 32(4): 1731-736.

Hastings, R. W. 1972. The origin and

seasonality of the fish fauna on a newjetty in the northeastern Gulf ofMexico. Unpub!. Ph.D. Dissertation,Fla. St. Univ., Tallahassee: 555 p.

Herrema, D. J. 1974. Marine and brackishwater fishes of southern Palm Beachand northern Broward counties, Flor­ida. M.S. Thesis, Fla. Atl. Univ., BocaRaton: 275 p.

Klima, E. F. 1959. Aspects of the biologyand the fishery for Spansih mackeral,Scomberomorus maculatus (Mitchill),of southern Florida. St. Fla. Brd.Conserv., Tech. Ser. No. 27: 4-39.

Marshall, R. 1958. A survey of thesnook fishery of Florida, with studiesof the biology of the principal species,Centropomus undecimalis (Bloch).Tech. Ser. Fla. Bd. Conserv., no. 22:1-37.

Miller, E. M. 1940. Mortality of fishesdue to cold on the southeast Floridacoast. Ecology 21(3): 420-421.

Miller, G. C. 1969. A revision of zoo­geographical regions in the warmwater area of the western Atlantic.In: Symposium on investigations andresources of the Caribbean Sea andadjacent regions. FAO Fish. Rept.,71. 1: 141 p.

Moe, M. A. and G. T. Martin. 1965.Fishes taken in monthly trawl samples'offshore off Pinellas County, Florida,with new additions to the fish faunaof the Tampa Bay area. Tulane Studiesin Zoo!' 12(4): 129-151.

Moore, R. H. 1976a. Observations onfishes killed by cold at Port Aransas,Texas, 11-12 January 1973. SouthwestNat., 20: 461-466.

-----. 1976. Seasonal patternsin the respiratory metabolism of themullets Mugil cephalus and Mugilcurema. Contrib. Mar. Sci., Vol. 20:133-146.

Moss, A. 1973. The response of plane-

head filefish, Monacanthus hispidis(Linnaeus), to low temperature. Chesa­peake Sci., 14(4): 300-303.

'owell, D., L. M. Dwinell.and S. E.Dwinell. 1972. An annotated listingof the fish reference collection at theFlorida Department of Natural Re­sources Marine Research Laboratory.Mar. Res. Lab., Fla. Dept. Nat. Re­sources, Spec. Rept. no. 36: i-179.

unckey, G. R. and C. H. Saloman.1964. Effect of reduced water tem­perature on fishes of Tampa Bay,Florida. Quart. J. Fla. Acad. Sci.27(1): 9-16.

R.obins, C. R. 1971. Distributionalpatterns of fishes from coastal andshelf waters of the tropical westernAtlantic. p. 249-255 In: Symposiumon investigations and resources of theCaribbean Sea and adjacent regions.FAO Fish. Res. Papers, 1971.

Smith, G. B. 1976. Ecology and distri­bution of eastern Gulf of Mexicoreef fishes. Fla. Dept. Nat. Res., Fla.Mar. Res. PubI. no. 19: 78 p.

Snelson, F. F., Jr. 1978. Mortality offishes due to cold on the east coast ofFlorida, January 1977. Fla. Sci., 19(1):1-12.

Southward, A. J. 1958. Note on the tem­perature tolerences of some intertidalanimals in relation to environmentaltemperatures and geographical distri­bution. Jour. Mar. BioI. Ass. U.K.,37: 49-66.

Springer, V. G. and K. D. Woodburn.1960. An ecological study of thefishes of the Tampa Bay area. Fla.St. Bd. Conserv. Prof. Pap. Ser., no.1: 1-104.

Starck, W. A., II. 1968 A list of fishesof Alligator Reef, Florida, withcomments on the nature of theFlorida reef fish fauna. UnderseaBioI., 1(1): 4-40.

Hypothermal mortality of fishes 97

_______ and R. E. Schroeder.1970. Stud. Trop. Oceanogr. (Miami),no. 10:1-224,44 figs.

. Storey, M. 1937. The relation betweennormal range and mortality of fishesdue to cold at Sanibel Island, Florida.Ecology 19(1): 10-26.

____ and E.. W. Gudger, 1936. Themortality of fishes due to cold atSanibel Island, Florida, 1886-1936.Ecology 17 (4): 640-648.

Tabb, D. C. 1958. Differences in theestuarine ecology of Florida watersand their effect on populations ofthe spotted weakfish, Cynoscion ne­bulosus (Cuvier and Valenciennes).Trans. 23rd N. Amer. wuai Conf.:392-401.

_____ . 1966. The estuary as ahabitat for spotted seatrout, Cynoscionnebulosus. Amer. Fish. Soc. Spec.Publ., no. 3: 59-67.

Verrill, A. E. 1901. A remarkable in­stance of the death of fishes, at Ber­muda, in 1901. Am. Jour. of Sci., 12:88.

Wetterhall, W. S. 1965. Reconnaissanceof springs and sinks in west-centralFlorida. Fla. Geol, Survey Rept. Inv.39: 1-42.

Whitehead, P. J. P. 1973. The clupeoidfishes of the Guianas. Bull. Brit. Mus.(Nat. Hist.) Zool., Supp. 5: 1-227,72 Fig., 6 Tables.

Willcox, J. 1887. Fish killed by coldalong the Gulf of Mexico and coast ofFlorida. Bull. U. S. Fish. Comm.6: 113.