fisheries General Outline 1. Introduction 2. Fisheries Science - - PowerPoint PPT Presentation

fisheries

General Outline

1. Introduction 2. Fisheries Science 3. Effects of Fishing 4. Fisheries Management

Types of Fisheries:

• Artisanal: traditional fishing effort involving

households; small-scale in economic input and effort; often associated with subsistence fishing, may be commercial in nature; usually local in effect.

• Commercial: capitalization of catch with a larger-

scale economic input and effort; usually larger than household group.

• Recreational: fishing for sport

How to catch a fish

• Hooks

– Rod and reel – Longlines

• Traps
• Nets
• Seines
• Gill nets
• Trawls
• Etc.
• Projectiles

– Spears – Harpoons

• Alternative methods

– e.g. Dyn-o-mite

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Gill nets

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History of Fishing

• Earliest fishing implements – bone harpoons

(90,000 yrs old) from Congo (2-m long catfish)

• Artisanal fishing efforts – extinction of Stellar

Sea Cows (1768)

• 1700-1900s: Whales, Seals, Otters, Turtles, Cod,

Herring, Haddock, etc.

• Industrial Revolution and Technological

Advancement

–Steam engine –Fleet development –Refrigeration –Transportation –Navigation –Detection Egyptian fish hooks Hawaiian net fishing

Fundamental Problems

• Overcapitalization
• Overfishing
• Long-term damage to marine ecosystems
• Extinction

Tragedy of the commons

• Garret Hardin, Science (1968)
• Scramble competition: when

many share a resource, the resource is at strong risk to get depleted (= species goes extinct) because the economical strategy is to get more than the others (=maximize gain).

• We see this problem in hunting/

fishing but also on grazing on public land.

Fisheries Science

• Roots in Population

Ecology

• Applied ecological

research that provides information for management structures

• Empirical Work
• Modeling

– Compensation/Depensation – Stock Assessments

“I believe that the cod fishery, the herring fishery, the pilchard fishery, the mackerel fishery, and probably all the great sea-fisheries are inexhaustible; that is to say, nothing we can do seriously affects the number of fish (Thomas Huxley 1883)”

Biological theory of exploitation N=population size K=Carrying capacity change of N per time t population growth rate Yield (Surplus of population)

• The logistic growth function can be

solved for Y and so we can get the surplus for known K and r.

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Allee effect positive correlation between population density and the per capita growth rate.

Fisheries Science

• Roots in Population

Ecology

• Applied ecological

research that provides information for management structures

• Empirical Work
• Modeling

– Stock Assessments – Compensation/Depensation – Allee Effect

Evolution of models reflects the evolution of our understanding of these systems

• Maximum Sustainable Yield (MSY): Maximum use that a renewable

resource can sustain without impairing its renewability through natural growth or replenishment

• Total Allowable Catch (TAC): Amount of catch managers allow to be

taken

• 1970s and early: logistic growth model, deterministic, no

environmental or stochastic variation

• 1980s: depensation – low survival at low density, stochasticity in

early life history, maximize MSY

• 1990s: precautionary – use MSY as limit
• 2000s: Ecosystem-based management

EBM

• length–age
• weight–length
• fecundity–length
• maturity–age
• spawner–recruit
• selectivity–age
• stochasticity
• species interactions
• environmental interactions

The Models: Summarized

Classical Neo-Classical Modern Ecosystem-Based Approaches

• length–age
• weight–length
• fecundity–length
• maturity–age
• spawner–recruit
• selectivity–age

Fisheries Impact:

“I believe that the cod fishery, the herring fishery, the pilchard fishery, the mackerel fishery, and probably all the great sea-fisheries are inexhaustible; that is to say, nothing we can do seriously affects the number of fish (Thomas Huxley 1883)”

FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS 2006

General Status of the World’s Fisheries

El Nino event

Halpern et al 2008

Pauly et al 2003

The Economic Issues

• Scramble Competition

– Tragedy of the Commons by Garrett Hardin (1968) – No advantage to helping your neighbor – No advantage to saving for later

• Unlimited access
• Growing demand on

limited resources

• Subsidies that stimulate
• vercapacity

U – underexploited D – moderately exploited M – fully exploited S – overfished R – recovering

Peruvian Anchovy Fishery

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Fisheries Science:

“I believe that the cod fishery, the herring fishery, the pilchard fishery, the mackerel fishery, and probably all the great sea-fisheries are inexhaustible; that is to say, nothing we can do seriously affects the number of fish (Thomas Huxley 1883)”

The Consequences of Overfishing

• Economic Collapse
• Extinctions due to overfishing

– Numerical – Ecological – By-Catch – catch of non-target species (generally discarded)

• Reduced Ecosystem stability
• Habitat Degradation
• Population viability: demographic/genetic change

Reductions of Top-Level Predators

Fishing Down the Food Web

Food Web 2 2.3 2.3 3.1 3.8

photo from www.daisymaefishing.com

Age distributions and reproduction

Life History Strategies: Age-structured schedules of mortality and reproduction

• Long-lived: late age at first reproductive

maturity

• Aggregation
• Low intrinisic rate of increase – offspring

number

• Differential reproductive value to older

individuals

• Strong association with specific habitat

Example: Rockfish Larval Abundances

Example: Red Hinds and Nassau Groupers in Bermuda

The Economic Issues

• Scramble Competition (Tragedy of the

Commons)

– No advantage to helping your neighbor – No advantage to saving for later

• Unlimited access
• Growing demand on limited resources
• Subsidies that stimulate overcapacity
• Ignorance about impact

Despite improvements in science, lag in action and lack of Closed management cycle causes problems

Why did this happen?

• Inaccurate estimates of population sizes

– Models descriptive, not predictive

• Parameters inaccurate (e.g. Catch-per-unit-effort (CPUE))

– Biology of species can drastically affect the assumptions of these models – Use of destructive fishing practices – Ignorance of ecosystem affects

• Inappropriate economic incentives
• Lack of political/social will

Modern approaches: Access

• Traditonal tools:

– Gear restrictions – Regulation of Catch and effort

• Access structure (limited entry into the race-to-

fish):

– Limited entry

• Regulate number of licenses
• Marine Protected Areas (MPAs)

– Individual quotas (IQs)

• Transferable (ITQs)
• Vessel (IVQs)

Modern approaches: Decision Making

• “Minister of Fisheries” (United Kingdom)

– Ultimate authority lies with the minister

• Council (USA)

– Appointed individuals from various sectors; try to build consensus but ruled by majority vote

• Commission (international)

– Representatives from membership councils

• All entities beginning to adhere to precautionary

axioms (risk management)

Modern approaches: Spatial Scales

• Unit Stock

– Fisheries can be defined into discrete independent units – Not biological or economically accurate – Evolutionary Significant Unit (ESU):

• (1) Substantially reproductively isolated from other conspecific

population units

• (2) Represent an important component in the evolutionary legacy of a

species

• Metapopulations

– population consists of interacting sub-populations – extinction/colonization – source-sink dynamics