fisheries management the practice - pelagicos · • population declines population size (biomass)...

Fisheries Management – The Practice

Stock Assessment

INPUTS:

OUTPUTS:

FISHING

Effort (fishing vessels, fishing hours)

Size / Age

Biomass

Fishing Mortality

Catch

CPUE

Fishery Management

INPUTS:

OUTPUTS: Fish Jobs, Profits

FISHING

Effort (& Technology)(Gas, Bait, Gear, Subsidies)

Externalities

Bycatch

Habitat Impacts

Are Sustainable Fisheries Achievable ?

(Chapter 15 - Hilborn 2005)

Economic Social

- Resource Ownership - Management Institutions

(property rights / traditions) (assessment, enforcement)

- Subsidies (gas / ice) - Pride / Ownership

Other Aspects of Sustainability:

Economic Basis / Social Basis

Principle 1. MSY curve

Result:

MSY occurs at B = K / 2

Population Size (Biomass)

Popula

tion C

han

ge

(dN

/ d

t)

0 KK / 2

Management Implications:

- Monitor B and vary

catches accordingly

- B msy: Maintain B at K/2

- F msy: Regulate Fishing

Mortality (% B)

Spawner – Recruit Relationships

The working conceptual model

for Bering Sea walleye pollock

is a survival gauntlet model

representing the successive

conditions or switches that must

be realized for the fish to survive.

Each switch has a conditional

probability for survival. The

probability is subject to spatial

and temporal variability in

physical / biological conditions...

and may be density-dependent.

Switch Model

(Quinn and Niebauer 1995)

Switch Model

Density-dependent and Density-independent Factors:

The “feeding larval switch" is dependent

on water temperature, which varies in

space and time. Switch acts on individuals

(density-dependent) and entire cohorts

(density-independent) (e.g., Starvation).

The “juvenile survivorship switch” is

influenced by density dependent

factors related to both the abundance

of the juvenile and the adult fish

(e.g., Cannibalism)

Spawner – Recruit Relationship

Conceptual Model of the Relationships Between Pollock

Recruitment and Biophysical Correlates in Southeast Bering Sea

Moderate density

dependence between the

spawning stock biomass

and the recruitment, with

reduced recruit survival at

high adult abundance

Spawner – recruit curve

suggests other driving

mechanisms because

several points are well

above and below the fitted

relationship.

Points way above the line

(1978, 1982, 1989)

are warm-water years(Bailey et al. 1996)

Marine Population Dynamics

(Chapter 4 – Levitan and McGovern 2005)

The Allee Effect:

“Decreases in population density result in

decreased per capita population growth”

Specially Exciting Examples:

Broadcast Spawning (Density) –> Abalone

Nursery Habitats (Cues / Refuges) –> Urchins

White Abalone (Haliotis sorenseni) Allee Effect

White Abalone Restoration:

On 2001, biologists placed 3 F and 2 M in separate

containers in the lab and added hydrogen peroxide.

Two hours later, 2 females spawned about 3 million

eggs, followed by release of sperm from one male.

Biologists mixed the eggs and sperm and obtained a

95 percent fertilization rate.

Once occurring in high

densities (1 per m square

of suitable habitat), recent

surveys show densities of

1-3 per hectare (10000

square m) in historical core

habitat (Channel Islands) (NMFS)

White Abalone - Harvesting and Decline

Surveys in Southern

California show

a 99% reduction in

density of white

abalone since 1970s

(Rogers-Bennett et al. 2002)

White Abalone - Recovery Project

Populations significantly declined in 1970s as the result of commercial

fishing and in 2001 became first marine invertebrate to be listed as an

endangered species. A recovery plan was developed by NOAA NMFS.

Recovery steps:

• prevent harvest, protect habitat, and survey wild populations

• propagate species in captivity

with goal of outplanting

larvae, juveniles, and adults

into their native range

Captive propagation hindered

by high mortality from

bacterial withering syndrome.

Allee EffectBelow minimum abundance threshold:

• There is no recruitment

• Population declines

Population Size

(Biomass)

Rec

ruit

men

t

0 KT

Threshold

Important in group living

animals, such as schooling

fishes. It may cause a

population to collapse if

harvesting pressure is too

strong, as has happened for

some pelagic fisheries.

(Courchamp et al. 1999)

CPUE f (B, E)

Population Size (Time T)

0 High

Cat

ch (T

ime

T)

0

H

igh

Principle 2. CPUE proportional to Biomass

In some instances, CPUE is not a good metric of Biomass

Limitations of CPUE

Other inputs go into fishery, and influence the ability to catch fish:

- Vessel size

- Vessel Type

(processors)

- Depth finders

- Thermistors

- Fish finders

- Other Technologies:

spotter planes, satellites

LimitationsIn some instances, CPUE is not a good metric of Biomass

Example: Stocks with high degree of aggregation

Fish density: 1 per sq km

In normal year:

Stock: 30 Area: 30

Catch 10

Effort 10

CPUE = 1



Fish density: 2 per sq km

In restricted habitat year:

Stock: 30 Area: 15

Catch 20

Effort 10

CPUE = 2



Fish density: 0.5 per sq km

In expanded habitat year:

Stock: 30 Area: 60

Catch 5

Effort 10

CPUE = 0.5



Fish density: 1.5 per sq km

In poor year:

Stock: 15 Area: 10

Catch 15

Effort 10

CPUE = 1.5


Example: Stocks with very restricted range / low motility

LimitationsYear 1: Catch 10, Effort 10 CPUE = 1 B = 25

LimitationsYear 3: Catch 5, Effort 10 CPUE = 0.5 B = 5

There are over 100,000 seamounts worldwide. Shallow seamounts

(height: 1000 – 3000 m) marked in red, deeper seamounts are in blue.

© Seung-Sep Kim / Chungnam National University

A seamount is an independent submarine mountain rising from

seafloor to at least 1,000 m above the seafloor.

Depending on the depth of the summit, seamounts can interact

with epi / meso – pelagic fish and squid species.

Is this a Realistic Scenario?Trawling on Seamounts: Pitcher et al. 2010

Technological advances have

deepened trawling impacts

Why Such a Slow Recovery ?

Habitat Destruction Population Dynamics

Are Sustainable Fisheries Achievable ?

(Chapter 15 - Hilborn 2005)

Vulnerability Rapid Population Growth

- Size: Maturity vs Recruitment - Fecundity

- Behavior: Schooling / Aggregation - Longevity (Age Maturity)

- Refugia: MPAs / habitat

Types of Biological Traits that

Support Sustainable Fishing:

Low Vulnerability / High Recovery

Marine scientists Make Call For

Seamount Closures For Research

Morato

et al. 2010

Global Fisheries & Marine Conservation:

Is Coexistance Possible?(Chapter 11 - Preikshot & Pauly 2005)

Injecting conservation-

oriented thinking into

fisheries management

implies strong emphasis

on no-take MPAs.

MPAs can buffer exploited

populations from effects

of environmental variation.

Global Fisheries & Marine Conservation:

Is Coexistance Possible?(Chapter 11 - Preikshot & Pauly 2005)

The socio-economical and ecological

implications / impacts of fishing

depend on the “scale” of the fisheries

3. Other Unwanted Consequences

The definition of

bycatch, as stated

in Magnuson-Stevens

Fishery Conservation

and Management Act:

NOAA Fisheries

uses the following

definition for its

National Bycatch

Strategy and bycatch

reduction efforts:

Two Approaches to Marine Conservation

(Rolf & Zacharias 2011)

Traditional: Novel:

- Species Focus - Ecosystem Focus

- Single species - Multi-species

- Fishery controls - Managing spaces

References

Bailey, K.M., R.D. Brodeur, and A.B. Hollowed. 1996.

Cohort survival patterns of walleye pollock (Theragra

chalcogramma) in Shelikof Strait, Alaska: A critical factor

analysis. Fish. Oceanogr. 5 (Suppl. 1): 179-188.

Quinn, T.J., II. and H.J. Niebauer. 1995. Relation of eastern

Bering Sea walleye pollock (Theragra chalcogramma)

recruitment to environmental and oceanographic variables.

pp. 497-507. In: Beamish, R.J. [ed], Climate Change and

Northern Fish Populations, Can. Spec. Publ. Fish. Aquat. Sci.

121, 739p.

Courchamp, F., Clutton-Brock, T., and Grenfell, B. 1999.

Inverse Density Dependence and the Allee Effect

Trends in Ecology & Evolution 14(10): 405-410.

North Atlantic Swordfish

Evidence of Shifting Baselines?

http://firms.fao.org/

firms/resource/10023/

The average North Atlantic

swordfish caught in the 1960s

weighed 300 pounds. By the late

1990s, the average was 100

pounds (NOAA - ICCAT).

History of Swordfish Fishery

1920s – Recreational fishery begins, primarily from Massachusetts to New York

1960s – Longline gear introduced in commercial fishery, replaces harpoons

1966 – International Convention for Conservation of Atlantic Tunas signed

creating International Commission for Conservation of Atlantic Tunas (ICCAT)

1970s – Recreational fishery develops in Florida

1990 – ICCAT passes first recommendation on swordfish, calling for harvest

reductions of undersized North Atlantic swordfish

1999 – ICCAT establishes 10-year rebuilding program

Managing Sliding Fisheries

Empirical Observations Modelling Efforts

Catch Data

(logbooks / observers)

Fishery Surveys

Stock-Recruitment Data

((NOAA Fisheries)

Recent History of Swordfish Management

2000/2001 – NOAA Fisheries implements several large time and area closures

for pelagic longline fishing to reduce bycatch of juvenile swordfish and billfish

2002 – Stock assessment determines stock biomass is 94 % of

level needed for maximum sustainable yield (BMSY)

2004 – NOAA Fisheries Service implements bycatch reduction

measures in commercial fishery (Goal: reduce take of small-size fish)

2006 – Stock assessment estimates that biomass approximately 99 % of BMSY

2007 – U.S. regulations establish baseline quotas and develop methods for

catch reporting of recreational fishers (Goal: do not overshoot the quota)

2009 – North Atlantic swordfish is considered fully rebuilt

Managing Sliding Fisheries

Empirical Observations Modelling Efforts

Catch Data

(logbooks / observers)

Fishery Surveys

Stock-Recruitment Data

((NOAA Fisheries)

Swordfish Boycott

Is there a problem?

Swordfish stocks in trouble

- starting in late 1990s.

What actions were taken?

U.S. NMFS set fishing limits, while

conservation groups organized swordfish

boycott by chefs and restaurants in 1998.

Did they succeed?

Boycotters claimed victory, claiming it

showed the power of market forces, but

fisheries managers disagree, saying

recovery was response to actions

implemented years before the boycott.

Swordfish Catch

2017SWO ATL Stock Assessment

www.iccat.int/Documents/Meetings/Docs/2017_ATL_SWO_ASS_REP_ENG.pdf

Abundance and Fishing Mortality

SCRS/2009/016 - SWO ATL Stock Assessment

www.iccat.int/Documents/Meetings/Docs/2009_SWO_ASSESS_ENG.pdf

F: Fishing Mortality (0 to 1)B: Biomass

(combined weight

of fish in population)

Swordfish Status

2017SWO ATL Stock Assessment

www.iccat.int/Documents/Meetings/Docs/2017_ATL_SWO_ASS_REP_ENG.pdf

Red Box:

Stock is overfished and

being overfished

Green Box:

Stock is not overfished

and not being overfished

Yellow

#1

Yellow

#2

What is going on in the

two yellow boxes?

References

FAO's report "Review of the State of World Marine Fisheries

Resources", tables D1-D17,

ftp://ftp.fao.org/docrep/fao/007/y5852e/Y5852E23.pdf

http://www.nmfs.noaa.gov/sfa/statusoffisheries/