UNIT 8:Fisheries

assessments

2

Fisheries dataWhy do we need fisheries data?FAO (2005): “Information is critical to EAF. It underpins the formulation of national policies, the development of management plans and the evaluation of management progress.”

Fisheries information can be biological, ecological, economic, social or cultural. It can be documented or oral history.Fisheries information tells us about

- Current fishery status- Fishery trends through time- Management effectiveness

All information types should be used where possible (scientific data – traditional knowledge). But remember, we will always be lacking information!

3

Data in the Pacific

Govan (2011): “To date the financial costs of scientific research and monitoring appear to have far exceeded investments in actual management of coastal areas. Using locally available information with simple approaches to community monitoring is a cost effective solution, and collaboration with government or regional technical agencies for generating highly technical and specific information such as stock assessment, is another.”

In the Pacific:• Simple data collection approaches will generally be warranted.• Need to identify approaches in consultation with stakeholders.

4

Data types

Traditional knowledge/anecdotes- simplest form of data- needs stakeholder/community consultation- collect using interviews with community members, especially elders or through community meetings- need wider community involvement- issues and management needs can be determined by consensus

5

Data typesCatch and effort dataCatch = how much is caught (weight or numbers)Effort = how long fishing; how many fishers; how many nets; length of nets

6

Data typesCatch and effort data• Use these to calculate Catch per Unit Effort (CPUE) = a measure of relative abundanceExamples: - number of sea cucmbers collected for every hour spent collecting them for each collector; - weight of a target species caught per hour of line fishing for each collector and each fishing line used

For example:Catch (C) = 36 kg; Effort (E) = 6 hours; Fishers (F) = 2CPUE = (C/E)/F = (36/6)/2 = 3 kg/fisher/hour

7

Data types

Size data• Measure weight and/or size of all fish caught (sub-sample)• Can be done by fishers themselves, landing sites or at markets• Calculate average size:

Average fish length = 253/7 = 36.14 cm

Totals

Fish # 1 2 3 4 5 6 7 7

Fish length (cm) 32 34 36 29 44 35 43 253

8

Data typesUnderwater Visual Surveys (UVS)• In-water (SCUBA or snorkel) surveys of fish/invertebrate numbers and/or habitats• Can collect:

• Species numbers per area (density = relative abundance) and sizes

• Species diversity• Habitat types and characteristics

This approach requires training and is more resource intensive

9

UVC sample data sheet

10

Data types

Biological samples• Includes gonads and otoliths• Determine sex, maturity, reproductive status, age & longevity• Derive:

• Sex ratios• Size/age at maturity• Spawning seasonality• Age structure• Growth rates• Mortality rates• Longevity

• Collecting data of this type requires resources and training.• Careful consideration of resources and management needs is required.

11

Data typesSocial/economic data• Why fisheries benefit communities• Can help ensure these benefits continue

• Data collected by interviews with community members• Data types include:• # of fishers, dependence on fisheries• income derived from fishing• % of total income derived from fishing• profitability• use of harvested fish• fishers’ involvement in decision-making

12

Data type How collected What used for Cost effectiveness

Traditional knowledge/anecdotes

Community meetings; individual surveys with elders

Important fishery sites; indication of historical fishery health (species,

sizes, locations); species life history

High

Catch and effort

Record fisher catch (numbers per species) and how long fished, either by surveys or

logbooks; regular fishing ‘surveys’ by fisheries officers

Catch-per-unit effort (CPUE) used as an

indicator of relative abundance; used to

determine population trends

Medium

Size

Fishers or fisheries officers record length and/or weight of fish caught; fish measured

in the marketplace

Average size (length or weight) can be calculated

and monitored across: species, years, areas, etc

Medium

Underwater Visual Surveys

SCUBA or snorkel transects to record species number, size,

habitat type, etc

Numbers/transect give an estimate of relative abundance; species

diversity; habitat changes. These can be

monitored through time to determine population

trends

Low

13

Data type How collected What used for Cost effectiveness

Traditional knowledge/anecdotes

Community meetings; individual surveys with elders

Important fishery sites; indication of historical fishery health (species,

sizes, locations); species life history

High

Underwater Visual Surveys

SCUBA or snorkel transects to record species number, size,

habitat type, etc

Numbers/transect give an estimate of relative abundance; species

diversity; habitat changes. These can be

monitored through time to determine population

trends

Low

Biological

Samples can be collected directly independently of fishers; samples can be

collected from fisher catches and/or marketplaces. Samples

include gonads and otoliths

Used to determine sex and age to derive: growth

rates, age/size at maturity, sex ratios, sex

change, fecundity

Low

Social/Economic Survey interviews with community individuals

Determine how fisheries benefit communities; derive strategies to

ensure benefits continue

High

14

Activity

DVD: Second half of Module 1

Activity 8.1: Identify examples of different fisheries data, how collected and how used in fisheries management?

15

Use of CPUERuss et al (2003) Apo Island,Philippines use of CPUE data

16

Use of size dataAverage fish size from local catches of grouper over an 11 year period.

A 35 cm minimum size limit was introduced in 2005 after community concerns of fewer and smaller fish.

2000 2002 2004 2006 2008 2010 20120

5

10

15

20

25

30

35

40

45

50

Year

Ave

rage

siz

e (c

m)

17

Use of UVS dataRuss et al (2003) Apo Island, Philippines: use of UVS data

18

IndicatorsIndicators & reference points• Many data types can be used as an Indicator• An indicator will inform us about changes in the resource

we are managing• It will also inform how well particular objectives are

being met• Based on the objective the desirable level of the indicator should be identified. This is called the target reference level.• Also, a level below which the indicator goes is undesirable should be identified. This is called the limit reference level.• How well the indicator is perfomring against reference levels is called the performance measure

19

Indicators

20

Use of indicatorsAn example of the use of UVS data at SPC workshop (see Box 13, SPC, 2010):

21

Other analyses

There are many other more complex analyses that use fishery data to describe populations dynamics including:• Growth• Mortality• Yield per recruit• Biomass dynamic models• Age structured models

These methods require robust data on size, age and catch• Should be used only in data- and resource-rich situations

Photo:Dave Welch

22

Unit review

Fisheries data are important to inform about:- Current fishery status- Fishery trends through time- Management effectiveness

Collection of data should be dictated by resource capability - Simple approaches are often needed

Indicators are the data we use to measure fisheries status and management perfromance

There are many different data types:

23

Unit review

Data type How collected What used for Cost effectiveness

Traditional knowledge/anecdotes

Community meetings; individual surveys with elders

Important fishery sites; indication of historical fishery health (species,

sizes, locations); species life history

High

Catch and effort

Record fisher catch (numbers per species) and how long fished, either by surveys or

logbooks; regular fishing ‘surveys’ by fisheries officers

Catch-per-unit effort (CPUE) used as an

indicator of relative abundance; used to

determine population trends

Medium

Size

Fishers or fisheries officers record length and/or weight of fish caught; fish measured

in the marketplace

Average size (length or weight) can be calculated

and monitored across: species, years, areas, etc

Medium

Underwater Visual Surveys

SCUBA or snorkel transects to record species number, size,

habitat type, etc

Numbers/transect give an estimate of relative abundance; species

diversity; habitat changes. These can be

monitored through time to determine population

trends

Low

Biological

Samples can be collected directly independently of fishers; samples can be

collected from fisher catches and/or marketplaces. Samples

include gonads and otoliths

Used to determine sex and age to derive: growth

rates, age/size at maturity, sex ratios, sex

change, fecundity

Low

Social/Economic Survey interviews with community individuals

Determine how fisheries benefit communities; derive strategies to

ensure benefits continue

High

24

Assessments

Activity 8.3: In two teams use simulated data to calculate some basic fisheries statistics. Report back on methods, results, and the relevance to management.

DVD: Fish and People Module 5: Fish and people: today and tomorrow

15 minute personal review: unit review, students to review main concepts of unit in the course notes, contribute any new words (new to them) to their own personal glossary in the back of their notebook (local language equivalent terms should also be recorded where possible)

25

HomeworkAnswer one of the following:

1. Describe a method that is used to assess a fishery that you are familiar with and explain how the information is used in management. Do you think it is effective, or do you think that there is a better way to do things?

2. If you had an unlimited amount of money, design a plan to collect data on a fishery you are familiar with. Once you have your plan, imagine that after a few years you lost the funding to collect all but one piece of the data-what one thing would you keep collecting and why?