shark nursery areas in the coastal waters of massachusetts · canis, 23 (6.2%) sandbar sharks...

American Fisheries Society Symposium 50:17–33, 2007© Copyright by the American Fisheries Society 2007

17

Shark Nursery Areas in the Coastal Watersof Massachusetts

GREGORY B. SKOMAL*

Massachusetts Shark Research Program, Division of Marine FisheriesCommonwealth of Massachusetts, Post Office Box 68

Vineyard Haven, Massachusetts 02568, USA

Abstract.—To identify and characterize shark nursery habitat in the coastal waters of Massachu-setts, longline and shark angler surveys were conducted from 1989 to 2002 in the neritic waters ofNantucket Sound, Massachusetts. Additional samples and information were opportunistically col-lected from recreational and commercial fishermen, as well as published sources. A total of 123longline sets of 5,591 hooks caught 372 sharks consisting of 344 (92.5%) smooth dogfish Musteluscanis, 23 (6.2%) sandbar sharks Carcharhinus plumbeus, and 5 (1.3%) dusky sharks C. obscurus.The sharks were taken during the period of 16 June–24 September in water temperature and depthranges of 16.0–27.2°C and 1.2–27.1 m, respectively. Longline catch rates (number of sharks perlongline set) were stratified by species, area, month, year, water temperature, and depth. Anglersurveys reported the capture of 294 sharks, including sandbar sharks (72%) and smooth dogfish(28%). Data from 540 neonatal and adult smooth dogfish ranging 27.5–121.0 cm fork length (FL)support the conclusion that the neritic waters of southern Massachusetts serve as primary nurseryhabitat for this species. Size and sex data from 235 juvenile sandbar sharks ranging 61.0–157.0 cmFL indicate that this region provides secondary nursery habitat for this species. Opportunistic samplesof juvenile sand tiger Carcharias taurus, white shark Carcharodon carcharias, basking sharkCetorhinus maximus, and tiger shark Galeocerdo cuvier provide evidence that these species utilizeMassachusetts coastal waters for secondary nursery habitat.

* E-mail: [email protected]

Introduction

With the exception of trawl, gill-net, and longlinefisheries that target spiny dogfish Squalusacanthias, there are no directed commercial fish-eries for sharks in Massachusetts. Of the 1,740metric tons (mt) of sharks landed in Massachu-setts in 2002, 99% were spiny dogfish and theremaining 1% (15.8 mt) consisted of pelagicsharks, including shortfin mako Isurus oxyrinchus,porbeagle Lamna nasus, and blue shark Prionaceglauca taken incidental to offshore trawl,longline, and gill-net fisheries. A substantial rec-reational fishery for sharks occurs off the coast ofMassachusetts from June through September eachyear. The most recent estimates from the NationalMarine Fisheries Service (NMFS) Marine Recre-ational Fishery Statistics Survey (MRFSS) indi-cate that Massachusetts’ recreational fishermencaught about 430,000 sharks in 2002, with spinydogfish comprising 99% of the catch. The MRFSSestimated that the balance of the catch included

blue sharks and shortfin makos as well as smoothdogfish Mustelus canis and sandbar sharksCarcharhinus plumbeus. Although Massachusettsrecreational fishermen target sharks, few arelanded; MRFSS estimated that 82% of the 2002catch was released.

There are indications that MRFSS data donot adequately reflect the extent to which sharksutilize the neritic waters of Massachusetts. Spe-cifically, the survey does not fully represent spe-cies composition, fails to generate accurateindices of relative abundance, and does little toidentify the temporal and spatial distribution ofsharks and shark nursery habitat in these waters.For example, it is well established that the sandtiger Carcharias taurus and dusky sharkCarcharhinus obscurus are seasonal migrants tosouthern New England (Bigelow and Schroeder1953); yet, their low abundance precludes de-tection by the survey.

The Massachusetts Division of Marine Fish-eries (DMF) established the Massachusetts SharkResearch Program (MSRP) in 1989 to more fullyelucidate the ecology, distribution, and relative

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abundance of sharks subjected to fisheries off thecoast of Massachusetts. The MSRP conducts an-gler and longline surveys as well as opportunisti-cally collects information from recreational andcommercial fishermen. Biological parameters,including age structure, feeding ecology, localmovements, and reproductive status, are exam-ined through dissection and tagging of sharkspecimens.

In the current study, information collectedby the MSRP from 1989 to 2002 was compiledand analyzed for the identification of primary andsecondary shark nursery habitat in the coastalwaters of Massachusetts. Bass (1978) defined pri-mary nursery habitat as areas where parturitionoccurs and neonatal sharks spend the first part oftheir lives, whereas secondary nursery areas arethose inhabited by slightly older, but not yet ado-lescent or mature sharks. It has been suggestedthat shark populations may be limited by theamount of suitable nursery habitat (Springer1967). Hence, information on nursery habitat isimportant to ensure adequate shark managementand to assess potential anthropogenic impacts onthese areas. The Final Fishery Management Planfor Atlantic Tunas, Swordfish, and Sharks identi-fied the need for this information and emphasizedthat without more basic research on life history,habitat use, behavior, and distribution, it will bedifficult to define essential fish habitat for sharkspecies (NMFS 1999). The plan also noted thepaucity of information correlating habitat use tophysical habitat characteristics (NMFS 1999).Hence, relative abundance data derived fromMSRP sampling were statistically analyzed in thecurrent study to investigate spatial and temporalcorrelations to the physical characteristics ofMassachusetts coastal waters. It is anticipated thatthe results of this study and others in this volumewill provide fisheries managers with contempo-rary information vital to shark conservation anddomestic management.

Methods

The Massachusetts coastline is divided by CapeCod into two general areas relative to shark nurs-ery habitat (Figure 1). In the western North Atlan-tic, Cape Cod represents the northern limit of thegeographic range of a few coastal shark species,which include the smooth dogfish, sandbar shark,dusky shark, and tiger shark Galeocerdo cuvier.

The major coastal water masses south of CapeCod include Buzzards Bay, Vineyard Sound, andNantucket Sound. Those shark species that pen-etrate coastal waters both north and south of CapeCod include spiny dogfish, sand tiger, white sharkCarcharodon carcharias, and basking sharkCetorhinus maximus. Cape Cod Bay and Massa-chusetts Bay are the major coastal water bodiesnorth of Cape Cod. Regardless of the region, theentire Massachusetts coastline is composed ofhundreds of bays and estuaries.

Although sharks were provided to the MSRPfrom coastal waters throughout the state, longlineand recreational surveys were actively conductedin Nantucket Sound and, more specifically, offthe eastern portion of Martha’s Vineyard Islandcalled Chappaquiddick Island. This report willprimarily focus on these areas.

Study site

Vineyard Sound is bordered to the east byMartha’s Vineyard Island and to the west by theElizabeth Islands; it joins Nantucket Sound inthe region of Woods Hole, Massachusetts (Figure1). Nantucket Sound is enclosed by Martha’s Vine-yard and Nantucket Islands to the south and CapeCod to the north. Both sounds flood to the east,ebb to the west, and have an average tidal rangeof 0.3–1.0 m, depending on geographic location.Depth in these water bodies is characterized bysignificant shoaling, broad areas less than 20 mdeep, and deep pockets up to 28 m. The Vineyardand Nantucket sounds feed several coastal baysand estuaries on Cape Cod and on the Elizabeth,Martha’s Vineyard, and Nantucket islands. Watertemperatures in the sounds and their associatedestuaries fluctuate seasonally from year to year,but range from freezing in the winter months to28°C in the summer, depending on location. Thecoastal beaches, bays, and estuaries associatedwith Nantucket and Vineyard sounds are affectedto varying degrees by anthropogenic activities,including boating, marinas, mooring fields, pri-vate docks and piers, road runoff, and fishing.

Chappaquiddick Island is connected to theeastern part of Martha’s Vineyard Island by a thinbarrier beach along its southern edge (Figure 2).This approximately 20-km2 island is bordered bythe Cape Poge Wildlife Refuge along its north-ern, eastern, and southern shorelines andEdgartown Harbor to the west. The eastern and

SHARK NURSERY AREAS IN THE COASTAL WATERS OF MASSACHUSETTS 19

CAPE COD BAY

NANTUCKET SOUND

VINEYARD SOUND

BUZZARDS BAY

ATLANTIC OCEAN

MASSACHUSETTS BAY BOSTON

CAPE COD

MARTHA’S VINEYARD NANTUCKET

CAPE ANN

42.0°

70.0°

50 km

FIGURE 1. Massachusetts coastal waters.

southern sides of the island (East and Southbeaches, respectively) support seasonal recre-ational surf fishing activities that catch sharks.The neritic waters of East Beach are part ofMuskegut Channel, a major connection betweenthe Atlantic Ocean and Nantucket Sound. SouthBeach has direct exposure to the Atlantic Ocean.

Cape Poge Bay is a large (ca. 8-km2) pristineestuary occupying the northern half of Chappa-quiddick Island (Figure 2). The estuary is a ho-mogeneous water mass with high tidal exchangethrough an inlet connected to the outer Edgar-town Harbor on its western side (Figure 2). Watertemperature and salinity (30–32 parts per thou-

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sand) do not differ from the surrounding coastalwaters of Nantucket Sound. Cape Poge Bay sup-ports substantial commercial and recreational fish-eries for shellfish and finfish. Although often usedas an anchorage, Cape Poge Bay is a relativelyshallow water body (<4 m) and remains a town-protected resource with minimal anthropogenicdisturbances.

Longline survey

Massachusetts Shark Research Program longlineswere set from mid-June through mid-Septemberof each year in two areas off Chappaquiddick Is-land: inside Cape Poge Bay and along East Beach.These areas were established to standardize sam-

pling at fixed sites where recreational fishermenroutinely target sharks. In some years, exploratorysets were deployed in other areas in NantucketSound. Longlines were typically 0.8 km in length,consisting of 6.3 mm braided nylon mainline and40–60 Japanese tuna hooks (size 9/0) on 1.5-mstainless steel cable gangions. Longlines werebaited with Atlantic menhaden Brevoortiatyrannus, squid Loligo sp., or Atlantic mackerelScomber scombrus from 1990 to 1994 and Ameri-can eel Anguilla rostrata from 1995 to 1999.Longline sets were typically allowed to fish for10–12 h during day or night, meaning that lineswere set in the morning and hauled before sunsetor set in the evening and hauled after sunrise.

CHAPPAQUIDDICK ISLAND

CAPE POGE BAY

EAST BEACH

SOUTH BEACH

MUSKEGUT CHANNEL

EDGARTOWN HARBOR 5.53.71.81.8

9.1

1km

41.42°70.47°

FIGURE 2. Chappaquiddick Island and Cape Poge Bay study area; isobaths (m) = 1.8, 3.7, 5.5, and 9.1.


Sharks caught on longlines were measured (forklength) and either tagged with standard NMFStags (‘M’ tags or blue Rototags) or retained fordissection. The latter involved the determinationof stomach contents and reproductive condition.

The relative abundance index of catch perunit effort (CPUE) was calculated from longlinedata to investigate temporal and spatial trends inshark distribution. Species-specific CPUE, de-fined as the number of sharks caught per hook,was calculated and stratified by area, month, year,time of day, sea surface temperature (SST), anddepth based on set information. When samplesizes were adequate, a one-way analysis of vari-ance (ANOVA) or t-test was used to test for sig-nificant differences (p < 0.05) in mean CPUEamong months (July–September), time of capture(day versus night), area of capture (East Beachversus Cape Poge Bay), and year (1990–2002).To investigate habitat use relative to physicalhabitat characteristics, catch rate correlations todepth of capture and water temperature were con-ducted with regression analysis.

Recreational angler survey

Since 1989, recreational surf anglers who rou-tinely target coastal sharks were asked to reportcatch information on a standardized survey form.This information included area of capture, dateand time of capture, disposition of catch, forklength, sex, and bait. Most angler survey partici-pants fished sharks along the eastern and south-ern shores of Chappaquiddick Island, Martha’sVineyard, but additional data were provided byCape Cod and Nantucket fishermen.

Opportunistic samples

Coastal sharks have been incidentally capturedor observed off Massachusetts and reported to theMSRP by recreational and commercial fishermen.In some cases, these sharks were provided to theMSRP for examination.

All lengths reported herein are fork length(FL). When necessary, total length was convertedto fork length using the published morphometricrelationships of Branstetter and Musick (1994)for the sand tiger, Francis and Duffy (2002) forthe basking shark, and Kohler et al. (1996) for thewhite shark. For smooth dogfish, FL was derivedfrom total length (TL) using the following rela-tionship: FL = 0.89(TL) – 1.26 (n = 105, r2 = 0.998,

p < 0.05). For all species sampled by the MSRP,reproductive stage (neonate, juvenile, adult) wasdetermined from published reports on lengths atbirth and maturity.

Results and Discussion

From 1990 to 2002, 123 longlines consisting of5,591 hooks were set in the primary sampling ar-eas of Cape Poge Bay (61 sets, 2,268 hooks) andEast Beach (54 sets, 2,879 hooks). Additional setsincluded South Beach (5 sets, 254 hooks), westof Cape Poge Bay (2 sets, 142 hooks), and Vine-yard Haven Harbor (1 set, 48 hooks). Catch-per-unit-effort indices for sharks caught by the MSRPlongline survey are summarized in Table 1 andFigure 3.

Several sharks were reported or provided tothe MSRP from 1989 to 2003. In many cases, thesereports entailed the casual observation of “a shark,”and this typically resulted in the inability to prop-erly identify the animal. However, some instancesresulted in photo documentation or the specimenbeing provided to the program. Data collected inthis manner have resulted in valuable nursery habi-tat information on the sand tiger, white shark, bask-ing shark, and tiger shark (Table 2).

Smooth dogfish

The longline survey caught smooth dogfish offEast Beach (72%) and in Cape Poge Bay (22%),as well as off South Beach (3%), west of CapePoge Bay (2%), and in Vineyard Haven Harbor(1%), but these percentages were not standard-ized by effort. Excluding the latter three areaswith low sample sizes, the average catch rate ofsmooth dogfish was significantly greater off East

TABLE 1. Smooth dogfish mean longline CPUE strati-fied by set location, time of day, and month, 1990–2002.

Variable CPUE SE Sets (N)

Cape Poge Bay 3.29 0.77 61East Beach 8.33 0.71 54South Beach 2.82 1.73 5West of Cape Poge Bay 5.64 0.24 2Vineyard Haven Harbor 10.42 0.00 1Day 3.96 0.74 40Night 6.36 0.71 83June 8.63 4.62 5July 4.11 0.92 39August 6.21 0.78 58September 5.84 1.20 21

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1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002

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No. HooksSmooth DogfishSandbarDusky

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Beach (8.3 sharks/100 hooks) than in Cape PogeBay (3.3 sharks/100 hooks, t = –4.76, p < 0.01;Table 1), indicating that smooth dogfish weremore abundant in Nantucket Sound than in theenclosed estuary. This is further substantiated bya weak, yet significant, positive relationship be-tween set depth and catch rate (Figure 4, r2 = 0.22,p < 0.01). Smooth dogfish were captured frommid-June through late September. Although JuneCPUE (8.6 sharks/100 hooks) was higher thanJuly (4.1 sharks/100 hooks), August (6.2 sharks/100 hooks), and September (5.8 sharks/100hooks), these differences were not statisticallysignificant (Table 1). With the exception of thelow and peak years of 1991 and 1996, respec-tively, smooth dogfish CPUE has ranged from 4.2to 8.2 sharks/100 hooks over the 13-year timeseries (Figure 3). Smooth dogfish were caught over

the broad SST range of 16–27°C, but catch rateswere weakly correlated with temperature in twoways. There was a weak, yet significant (r2 = 0.15,p = 0.03) linear increase in catch rates to 21°C,followed by a equally significant (r2 = 0.24, p <0.01) decline in catch rates at higher tempera-tures (Figure 5). Longlines caught significantlymore smooth dogfish at night (6.4 sharks/100hooks) than during the day (4.0 sharks/100 hooks,t = –2.26, p = 0.03; Table 1), supporting the con-clusion that the species is more active at night(Casterlin and Reynolds 1979). Smooth dogfishcaught on longlines ranged from 63.0 to 121.0cm FL, and 97% were female.

From 1989 to 2002, the MSRP examined 540smooth dogfish consisting of fish caught by thelongline (337) and angler (82) surveys, takenduring other DMF sampling programs (82), and

FIGURE 3. Annual longline sampling effort and shark catch per unit effort in coastal waters of Massachusetts, 1990–2002; number in bar = number of longline sets.

TABLE 2. Sharks sampled by the Massachusetts Shark Research Program from Massachusetts coastal waters, 1989–2002.

Species N Tagged Size range (cm FL) Neonates Juveniles Adults Unknown

Smooth dogfish 540 146 27.5–121.0 91 12 356 81Sandbar shark 235 33 61.0–157.0 167 5 63Sand tiger 10 87.4–132.0 5 5Dusky shark 5 2 175.0–254.0 3 1 1White shark 1 109.4 1Basking shark 7 310.0–695.5 6 1Tiger shark 1 133.0 1


provided by commercial fishermen (39). Althoughsmooth dogfish are routinely captured by recre-ational anglers, they are released and not recordedby most survey participants. Smooth dogfish weremostly (424) sampled from the neritic waters ofChappaquiddick Island and Cape Poge Bay, butsamples also came from other parts of NantucketSound. The size range of all smooth dogfish

sampled by the MSRP was 27.5–121.0 cm FL (Fig-ure 6). The smooth dogfish sampled from Massa-chusetts waters consisted of primarily neonatesand adults based on the lengths at birth and ma-turity estimates of Conrath and Musick (2002)and Conrath et al. (2002) (Table 2; Figure 6). Ofthe adults, females (95%) were 85.0–121.0 cmFL and males (5%) were 71.0–99.0 cm FL. The

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0 1 2 3 4 5 6 7 8 9 10 11

Depth (m)

CP

UE

(sha

rks/

100

hook

s)

CPUE = (0.41(Depth) + 0.04)2

r2 = 0.22, p < 0.01

FIGURE 4. Relationship between longline set depth and smooth dogfish catch per unit effort; CPUE = (0.41(Depth)+ 0.04) 2, r2 = 0.22, p < 0.01.

0

5

10

15

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15 16 17 18 19 20 21 22 23 24 25 26 27 28

Temperature (°C)

CP

UE

(sha

rks/

100

hook

s) CPUE = 1.65(°C) - 25.32

r2 = 0.15, p = 0.03 CPUE = -2.53(°C) + 63.69r2 = 0.24, p < 0.01

FIGURE 5. Relationship between water temperature and smooth dogfish longline catch per unit effort showing linearincrease [CPUE = 1.65(Temperature) – 25.32, r2 = 0.15, p = 0.03] in catch rate to 21°C followed by a linear decline[CPUE = –2.53(Temperature) + 63.69, r2 = 0.24, p < 0.01] in catch rate at higher temperatures.

24 SKOMAL

neonates ranged 27.5–41.9 cm FL and compriseda more even sex ratio of 48% females. Similarly,Rountree and Able (1996) reported the near-ab-sence of (non-neonatal) juveniles in a New Jer-sey estuary.

In the northern end of its range, the smoothdogfish moves into the neritic waters of NantucketSound, Vineyard Sound, Buzzards Bay, and asso-ciated estuaries in late May and early June togive birth. Neonates were captured in NantucketSound and Cape Poge Bay during the period of20 June–14 August. Conrath and Musick (2002)reported that parturition occurs in May in thespecies, while Bigelow and Schroeder (1953) andRountree and Able (1996) presented a more pro-tracted period of mid-May through July. Basedon the size of neonates and time of capture, it islikely that parturition occurs in June and July inMassachusetts waters. Rountree and Able (1996)suggested that adults use Mid-Atlantic Bight es-tuaries and inshore coastal waters as parturitiongrounds. The presence of adult females and neo-nates in Massachusetts estuaries and inshorecoastal waters supports a similar conclusion forthis species in the northern end of its range. Thisis substantiated by the capture of neonatalsmooth dogfish in Nantucket Sound by commer-cial trawlers. One notable catch on 28 June 1994

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26 30 34 38 42 46 50 54 58 62 66 70 74 78 82 86 90 94 98 102 106 110 114 118 122Length Group (cm FL)

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Sex unknown (23)Female (248)Male (54)

Male Female

consisted of close to 2,000 dogfish pups taken ina discrete area 3 km off the northeast shore ofNantucket Island at a depth of 9–12 m. Sixty-three fish sampled from this catch ranged 28.0–36.0 cm FL, clearly overlapping the estimatedsize at birth of 25.0–34.0 cm FL (Conrath andMusick 2002). It is likely that Buzzards Bay,Nantucket Sound, Vineyard Sound, and their as-sociated bays and estuaries provide importantprimary nursery habitat for young-of-the-yearsmooth dogfish.

The virtual absence of adult males (3%) inlongline catches provides little evidence for in-shore mating. However, in this study, 31% of thesmooth dogfish caught by commercial trawlersin the deeper waters of Nantucket Sound wereadult males. Moreover, large aggregations of maleand female smooth dogfish have been observedin the upper reaches of Cape Poge Bay in mid- tolate June. In June 1992, smooth dogfish in one ofthese aggregations displayed behavior that maybe associated with mating activity. Several smallermales were observed at the surface biting andharassing solitary larger females. While the maleseluded longline gear, several females were ob-tained and mating wounds were apparent. Sincethis behavior is typical of mating elasmobranchs(Pratt and Carrier 2001), this is likely the first

FIGURE 6. Sex-specific length frequency distribution of smooth dogfish sampled by the Massachusetts SharkResearch Program, 1989–2002. Size at sexual maturity is shown for each sex (dotted lines) and (N) = total number ofsharks sampled.


known report of mating behavior observed in thisspecies.

The smooth dogfish is a seasonal migrant andgenerally remains in inshore Massachusetts wa-ters until October when it moves offshore andsouth. Of the 146 smooth dogfish tagged to date,4 (2.7%) have been recaptured (Nancy Kohler,NMFS, Rhode Island, personal communication).Three of these fish were recaptured off the coastsof Rhode Island (1.7 years, May), New Jersey (2.2years, October), and Virginia (1.8 years, May). Oneof these sharks was tagged and recaptured in CapePoge Bay after 4.1 years at liberty, possibly dem-onstrating site fidelity to a nursery area.

Sandbar shark

Longline CPUE for this species ranged from 0.0to 3.3 sharks/100 hooks over the 13-year period(Figure 3). However, so few sandbar sharks havebeen taken on longline each year that a singlefish could significantly influence CPUE. The high-est catch rate of 3.3 sandbar sharks/100 hooks in1991 was driven by two sandbars taken on a singleset in Cape Poge Bay. When one considers thenumber of variables that can influence the pres-ence of a species in a particular area, this indexmust be viewed with caution relative to this spe-cies. Nonetheless, the data do have some ecologi-cal implications. All of the sandbar sharks takenon longline were caught in SST and depth ranges

of 20–24°C and 2.4–6.4 m, respectively. Simi-larly, Carlson (1999) did not catch juvenile sand-bar sharks in the nursery areas of the northeasternGulf of Mexico until water temperatures reached22°C. In the current study, 23 sandbar sharks werecaptured on longline from 1 July to 5 Septemberoff East Beach (56%) and in Cape Poge Bay(43%). As noted above, sample size limitationsprecluded the statistical analysis of catch rates,but night sets appeared to catch more sandbarsharks (0.68 sharks/100 hooks) than day sets (0.21sharks/100 hooks).

During the period of 1989–2002, 212 sand-bar sharks were reported to the MSRP by recre-ational anglers (Figure 7). Although the sandbarshark is less abundant than the smooth dogfish,more were reported by anglers because the latterwas considered a nuisance fish and not recorded,thereby resulting in reporting bias. Most of thesandbar sharks were taken off East Beach (85%),but others were caught off South Beach (5%), inCape Poge Bay (2%), and off the south shore ofCape Cod (8%). The proportional catch of sand-bar sharks from these areas is indicative of surveyeffort and not relative abundance. Published re-ports of sandbar sharks from the south side ofCape Cod and off Nantucket Island provide evi-dence that the distribution of this species is morewidespread in Nantucket Sound than portrayedby this survey (Bigelow and Schroeder 1953;

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1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002

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FIGURE 7. Number and sex ratio of sandbar sharks reported to the Massachusetts Shark Research Program byrecreational fishermen, 1989–2002; (N) = total number of sharks sampled.

26 SKOMAL

Andrews 1973). Moreover, the rapid decline insandbar shark reports from 1997 to 2002 is likelydue to the dramatic decrease in effort associatedwith beach closures for nesting birds. All the sand-bar sharks reported to the MSRP were caught be-tween 21 June and 2 October.

In total, 235 (88 males, 63 females, 84 un-known) sandbar sharks were examined or reportedto the MSRP since 1989 (Table 2; Figure 8). Al-though sandbar sharks were taken between 21June and 2 October, the species was most abun-dant in July (Figure 9). The size range of thosesharks measured was 61.0–157.0 cm FL with nosexual differences (Figure 10). If size at maturity

is 143.0 cm FL and 149.0 cm FL for males andfemales, respectively (Sminkey and Musick1995), then 5% of the males and 2% of the fe-males sampled over the 13-year period were ma-ture. Based on the age estimates of Casey et al.(1985) and Sminkey and Musick (1995), the sand-bar sharks sampled over the 13-year period rangedfrom 2 to 15 years of age. Thus, the majority ofsandbar sharks occurring inshore in Massachu-setts are juveniles utilizing these areas as sec-ondary nurseries.

Sandbar sharks move out of Massachusettscoastal waters in early October, which likely co-incides with seasonal cooling of inshore waters.

NANTUCKET SOUND

VINEYARD SOUND

MARTHA'S VINEYARD

CAPE COD

9.1

9.1

5 km

41.5°

70.5°

FIGURE 8. Capture locations of sandbar sharks (N = 235) sampled by the Massachusetts Shark Research Program;isobaths (m) = 1.8, 3.7, 5.5, and 9.1.


Merson and Pratt (2001) reported that sandbarsharks moved out of the nursery habitat of Dela-ware Bay by early October. In the current study,33 sandbar sharks were tagged and 3 were recap-tured. The recapture rate of 9.1% is higher thanthat reported for this species (4.7%) by Kohler etal. (1998). These three fish were at liberty for 6–9years and recaptured off the coasts of Florida(January, July) and Texas (July).

Sand tiger

Despite their historical abundance in NantucketSound, no sand tigers were caught during the 13-year history of the longline survey. However, 10sand tigers have been reported to the MSRP since1989. Eight of these were taken by recreationalfishermen, one was entrained by the intake linesof a power plant, and one was photographed by arecreational diver; all were reported during themonths of August to October.

Along with the dogfishes, the sand tiger wasonce considered the most abundant shark in Mas-sachusetts coastal waters (Bigelow and Schroeder

1953). In the early 1900s, sand tigers supported acommercial fishery in Nantucket Sound until itwas thought to be locally exhausted (Bigelowand Schroeder 1953). Photographs provided tothe MSRP by the Nantucket Historical Societyconfirmed that this fishery landed large adult sandtigers. Although considered “the most commonof the large sharks” off Nantucket by Andrews(1973), not a single adult sand tiger has been re-ported to the program since its inception in 1989,despite the extensive commercial and recreationalmultispecies fisheries in this state. This providesevidence that intensive commercial fisheries canlead to the long-term depletion of local sharkpopulations.

The 10 sand tiger sharks were reported fromtwo general locations in coastal Massachusetts(Figure 11): south of Cape Cod in coastal watersoff East Beach, Chappaquiddick Island and frombays and estuaries in Massachusetts Bay. All ofthese were small immature sand tigers in the sizerange of 87.0–132.0 cm FL; the five sexed wereall female. According to the length-at-age esti-mates of Branstetter and Musick (1994), these fish

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Month

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Sex unknown (84)

Female (63)

Male (88)

FIGURE 9. Monthly distribution of sandbar sharks sampled by the Massachusetts Shark Research Program, 1989–2002; (N) = total number of sharks sampled.

28 SKOMAL

ranged in age from 0 to 2 years. In the westernNorth Atlantic, the sand tiger gives birth fromDecember through March and length at birth is85.3 cm FL (Gilmore et al. 1983). Five of the sandtigers sampled by the MSRP were 87.0–91.0 cmFL, close to or in their neonatal stage. Bigelowand Schroeder (1953) reported that most sand ti-gers caught from the northern part of their rangeare immature, with the exception of those takenin the aforementioned Nantucket fishery. There-fore, the coastal waters of Massachusetts providesecondary nursery habitat for sand tigers thatmove north from southeastern pupping grounds(Gilmore et al. 1983).

Dusky shark

From 1989 to 2002, only five dusky sharks havebeen sampled by the MSRP and these were takenon longline (Table 2; Figure 12). These sharkswere caught in SST and depths ranging 17–24°Cand 4.8–19.2 m, respectively. Four were capturedalong East Beach and one was taken off SouthBeach in deeper water (Figure 12). Of the fourreliably measured, three (two females, one male)were in the size range of 173.0–183.0 cm FL andone female was 254.0 cm FL. Based on the size at

maturity estimates of Springer (1960), the threesmaller dusky sharks were immature and the largerfemale had reached maturity. Although Bigelowand Schroeder (1953) examined 12 dusky sharksfrom Woods Hole, Massachusetts, including sixtaken in August of 1944, the species is not com-mon in southern New England. Nonetheless, thesouthern coastal waters of Massachusetts mayprovide secondary nursery habitat to those duskysharks that venture north.

White shark

In August 2002, a small white shark (ca. 109.0 cmFL) was captured in a trawl net and reported tothe MSRP. The commercial vessel was bottomtrawling in Vineyard Sound (Figure 11) at a waterdepth of 18–21 m and an SST of 21.1°C. Thewhite shark is a seasonal migrant to the coastaland offshore waters of New England (Bigelow andSchroeder 1953), and each year, the MSRP fieldsanecdotal reports of white sharks, which in mostcases are misidentified. Casey and Pratt (1985)reviewed the distribution of the white shark inthe western North Atlantic and noted that thisspecies is most abundant in the Mid-Atlantic Bighton the continental shelf between Cape Hatteras,

0

2

4

6

8

10

12

14

16

1860 64 68 72 76 80 84 88 92 96 100

104

108

112

116

120

124

128

132

136

140

144

148

152

156

160

Length Group (cm FL)

Num

ber o

f Sha

rks


Male Female

FIGURE 10. Sex-specific length frequency distribution of sandbar sharks sampled by the Massachusetts SharkResearch Program, 1989–2002. Size at sexual maturity is shown for each sex (dotted lines) and (N) = total number ofsharks sampled.


North Carolina and Cape Cod, Massachusetts.Moreover, they observed that more young whitesharks have been caught in this region than inany area of comparable size in the world. Bigelowand Schroeder (1953) reported two very smallwhite sharks, one harpooned off Boston in 1948(ca. 81.0 cm FL) and one netted off Rhode Islandin 1939 (ca. 138.0 cm FL). The five smallest whitesharks reported by Casey and Pratt (1985) fromthe Atlantic ranged from 109.0 to 123.0 cm FL.Uchida et al. (1996) and Francis (1996) estimatedthat length at birth of the white shark is 108.0–136.0 cm FL. Therefore, the white shark exam-ined in 2002 was one of the smallest reported

free-swimming white sharks and clearly a young-of-the-year animal. Casey and Pratt (1985) pos-tulated that white sharks use the neritic waters ofthe Mid-Atlantic Bight as a nursery area. Theirobservations coupled with those of Bigelow andSchroeder (1953) and the current study warrantthe inclusion of Massachusetts coastal waters inthis broad nursery region.

Basking shark

In the western North Atlantic, the basking sharkis known to concentrate in the spring and sum-mer in areas of high productivity and along ther-mal fronts on the continental shelf from southern

CAPE COD BAY

MASSACHUSETTS BAY

NANTUCKET SOUND

BUZZARDS BAY

70.0°

42.0°

30 km

FIGURE 11. Capture locations of sand tigers (n = 10, open squares) and a juvenile white shark (filled circle) sampledby the Massachusetts Shark Research Program, 1989–2002.

30 SKOMAL

New England to Newfoundland (Templeman1963; Owen 1984; Lien and Fawcett 1986). Thebasking shark is well documented off the coast ofMassachusetts (Bigelow and Schroeder 1953;Owen 1984). Basking shark reports to the MSRPhave ranged from the coastal waters of BuzzardsBay, Vineyard Sound, Cape Cod Bay, and Massa-chusetts Bay to the offshore waters of the GreatSouth Channel and Stellwagen Bank. Very littleis known of the size and age structure of the bask-ing shark population in these waters, but it isthought to consist of juveniles and adults. From1984 to 2003, seven stranded or incidentally cap-tured basking sharks (three males, four females)

were examined by the MSRP and/or NMFS per-sonnel (Lisa Natanson, NMFS, Rhode Island, per-sonal communication). Six of these fish strandedin Cape Cod Bay (3), in Boston Harbor (1), onMartha’s Vineyard (1), and on the east side of CapeCod (1), while one was entangled in a trawl net inthe Great South Channel east of Nantucket. Malesranged from 320.0 to 696.0 cm FL and femalesranged from 310.0 to 690.0 cm FL. Size at matu-rity is thought to be 691.0 cm FL and 700.0 cmFL in males and females, respectively (Mathews1950). Hence, two of the males and all four of thefemales were immature. The coastal and offshorewaters of southern New England, therefore, pro-

MARTHA'S VINEYARD

41.5°70.5°

5 km

FIGURE 12. Capture locations of dusky sharks sampled by the Massachusetts Shark Research Program, 1989–2002;isobaths (m) = 1.8, 3.7, 5.5, and 9.1.


vide important secondary nursery habitat for thisplanktivorous species. The extent to which thisregion serves as primary nursery habitat is un-known because neonates and pregnant femaleswere not observed.

Tiger shark

The tiger shark is generally reported from tropicaland warm temperate waters of the western NorthAtlantic, but it is rarely encountered north of theMid-Atlantic Bight. Bigelow and Schroeder (1953)reported the capture of juvenile tiger sharks in thenearshore waters of Woods Hole (presumably Vine-yard and Nantucket sounds) “every year.” From1987 to 2002, five tiger sharks were recorded byoffshore fishing tournaments based in Massachu-setts, but all were caught several miles south ofMartha’s Vineyard and Nantucket islands. In June2001, a juvenile female tiger shark (133.0 cm FL)was taken by a recreational fisherman off SouthBeach on Martha’s Vineyard. Although historicallypresent, tiger sharks have been rare in recent years,as is their utilization of Massachusetts coastal wa-ters for secondary nursery habitat.

Conclusions

Data collected and compiled from 1989 to 2003by the MSRP indicate that the coastal waters ofMassachusetts provide important nursery habi-tat for several species of sharks.

For the smooth dogfish, sandbar shark, duskyshark, and tiger shark, this region represents thenorthern limit to their geographic range in thewestern North Atlantic. For the sand tiger, bask-ing shark, and white shark, these inshore nurseryareas may extend farther north into the Gulf ofMaine. In all cases, future management to protectshark nursery habitat for these species should in-clude the coastal waters of Massachusetts.

The presence of adult and neonatal smoothdogfish in Nantucket Sound and its associatedbays and estuaries suggests that these areas pro-vide important primary nursery habitat for thisspecies. Moreover, it is highly likely that Buz-zards Bay and Vineyard Sound serve a similar rolesince this species is known to occur in both. Thisregion also provides suitable opportunities formating.

The seasonal occurrence of juvenile sandbarsharks off Chappaquiddick Island, in Cape Poge

Bay, and off Cape Cod and Nantucket beachessuggests that the neritic waters of NantucketSound and its associated bays and estuaries pro-vide secondary nursery habitat for this species.Although the lack of angler reports from Buz-zards Bay and Vineyard Sound indicates thatthese water bodies do not play a similar role, thiscannot be said with certainty without an expan-sion of the survey. The apparent higher relativeabundance of juvenile sandbar sharks in thecoastal waters of Chappaquiddick Island may bea function of effort or may be related to the pris-tine nature of this area. The extent to which thesouthern beaches and bays of Cape Cod contrib-ute to the ecology of this species is not fully un-derstood. These areas are known to suffer fromgreater anthropogenic effects than Chappa-quiddick Island (Bowen and Valiela 2001), andthis may influence the relative abundance of sand-bar sharks in these areas. Great South Bay (LongIsland, New York) was once a primary nursery forthe sandbar shark (Nichols 1916; Thorne 1916),but the species is no longer found in this well-developed embayment (Merson and Pratt 2002).Similarly, Grubbs and Musick (2002) hypoth-esized that the low abundance of sandbar sharksin lower western portions of Chesapeake Bay maybe related to habitat degradation associated withrelatively higher levels of urbanization in thisarea. Additional research is needed to assess thetemporal and spatial effects of water quality onshark nursery habitat.

The occurrence of neonatal and juvenile sandtigers in the coastal areas of Massachusetts indi-cates that these waters serve as secondary nurseryhabitat for this species. Similarly, this is the firstreport to document secondary nursery habitat forthe dusky shark, tiger shark, and white shark inMassachusetts. However, the extremely low oc-currence of these species in this region may beindicative of low population sizes or annual fluc-tuations in habitat suitability. Much of the biol-ogy of the basking shark remains a mystery, butthe seasonal occurrence of juveniles in Massa-chusetts coastal and offshore waters warrants thedesignation of secondary nursery habitat in thisregion.

Acknowledgments

The MSRP is supported with funds from the Fed-eral Aid in Sportfish Restoration Act (Project F-

32 SKOMAL

57-R). These efforts would not have been pos-sible without the able and (mostly) willing sea-sonal assistance of Bob Fuller, Erin Rechisky,Steve West, Rob Goodwin, and Brian Teaman. Iappreciate the efforts of Jeremy King of DMF’sResource Assessment Program for providing catchand size data. I would also like to thank the mem-bers of the Martha’s Vineyard Surfcasters Asso-ciation and the countless volunteers who cameforward and hauled longlines, provided samples,and filled out surveys. Paul Schultz, Paul Brewer,David Pothier, and Hank Unzcer are notableMartha’s Vineyard surf fishermen who should becommended for taking the time to write downinformation and save shark parts for the local bi-ologist. This is Massachusetts Division of Ma-rine Fisheries Contribution No. 13.

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shark nursery areas in the coastal waters of massachusetts · canis, 23 (6.2%) sandbar sharks...

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