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

Gill nets 8

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History of Fishing Egyptian fish hooks • Earliest fishing implements – bone harpoons Hawaiian net fishing (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

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 “ 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)” • Roots in Population Ecology • Applied ecological research that provides information for management structures • Empirical Work • Modeling – Compensation/Depensation – Stock Assessments

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

• The logistic growth function can be solved for Y and so we can get the surplus for known K and r.

Allee effect positive correlation between population density and the per capita growth rate. 17

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

The Models: Summarized •length–age •weight–length •fecundity–length •maturity–age •spawner–recruit •selectivity–age Classical Neo-Classical EBM •length–age Ecosystem-Based •weight–length Approaches •fecundity–length •maturity–age •spawner–recruit •selectivity–age •stochasticity Modern • species interactions • environmental interactions

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)”

General Status of the World’s Fisheries El Nino event FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS 2006

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 overcapacity

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 3.8 3.1 2.3 2 2.3

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