Fisheries Management Final :(

Fisheries management

The process of controlling fishery activities through data collection, planning, decision-making, and enforcement to ensure sustainability

Fishery

Activity involving harvesting wild fish or raising fish through aquaculture

Fishery unit

A defined group including fishers, species, gear, area, class of boat, and purpose of fishing

Fisheries management authority

Organization responsible for regulating fisheries, collecting data, enforcing rules, and allocating resources

Fish stock

A discrete, self-sustaining population of a species from which catches are taken

Stock assessment

Scientific evaluation of fish stock status, including size, yield, and exploitation level

Sustainability

Ensuring long-term productivity of fishery resources

Biological objective

Management goal focused on conservation, rebuilding stocks, and preventing species mortality

Economic objective

Goal to maximize profits, income, and reduce variability in fisheries

Social objective

Goal to ensure food security, employment, and community well-being

Political objective

Goal to maintain government support and generate revenue

Indicator

Quantitative measure used to track progress toward management objectives

Target

A specific value of an indicator used as a management goal

Management strategy

A blueprint outlining monitoring, rules, and enforcement in a fishery

Harvest control rule

A guideline that determines how fishing pressure changes based on stock status

Effort control

Regulation limiting fishing activity (e.g., number of boats)

Catch control

Regulation limiting total catch in a fishery, implemented using tools like TAC

Technical measures

Regulations like mesh size, closures, and gear restrictions

Fisheries management cycle

Process where society sets objectives, scientists advise, and managers implement strategies

Boom and bust cycle

Pattern of fishery development, overexploitation, collapse, and potential recovery

Industrialization in fisheries

Increased fishing capacity and demand due to technological advancements

Global fisheries period

Worldwide exploitation and integration of fisheries into global markets

Population vulnerability

Susceptibility of fish populations to fishing pressure based on traits

Life-history traits

Characteristics like growth rate, age at maturity, and fecundity affecting survival and reproduction

Behavioral traits

Species behaviors (e.g., schooling, migration) affecting catchability

Fishing impacts on populations

Changes in size, age, reproduction, and genetics due to fishing

Fishing impacts on communities

Changes in diversity, structure, and species interactions

Trophic cascade

Chain reaction in ecosystems caused by removal of key species (e.g., predators)

Fishing down the food chain

Trend of targeting lower trophic level species over time

Community stability

Ability of an ecosystem to resist or recover from disturbances

Resistance

Ability of a system to withstand change

Resilience

Speed at which a system returns to its original state

Reactivity

Magnitude of change after disturbance

r-selected species

Species with fast growth, early reproduction, and many offspring

K-selected species

Species with slow growth, late maturity, and few offspring

Logistic growth

Population growth that slows as it approaches carrying capacity

dN/dt = rN(1-N/K) Where: N = population size, r = intrinsic growth rate, K = carrying capacity

Rmax

Maximum population growth rate, indicating recovery potential

Carrying capacity (K)

Maximum population size an environment can sustain

CPUE (Catch per Unit Effort)

Measure used as an index of abundance. shown as C/E = qN where C = catch, E = effort, q = catchability, N = abundance

Catchability (q)

Efficiency with which fish are captured; C = qEN, higher q = easier to catch fish, depends on gear/behavior/technology

Fisheries independent data

Data collected through scientific surveys

Fisheries dependent data

Data collected from fishing activities (e.g., logbooks)

Gear selectivity

Tendency of fishing gear to catch certain sizes/species

Length-weight relationship

Equation describing fish weight as a function of length; commonly modeled as W = aL^b

Growth coefficient (b) in length-weight relationship

b = 3 indicates isometric growth, b > 3 indicates fish become relatively heavier with size, and b < 3 indicates fish become relatively thinner with size

Von Bertalanffy growth model

Mathematical model describing individual fish growth over time; predicts length as a function of age and approaches a maximum asymptotic size (L∞). Parameters include K (growth rate) and t₀ (theoretical age at zero length). typically shown as Lt=L∞(1-e^-K(t-t0))

Natural mortality (M)

Rate at which fish die from natural causes

Fishing mortality (F)

Rate at which fish are removed by fishing, shown as F = Z - M

Total mortality (Z)

Sum of natural and fishing mortality, shown as Z = F + M

Surplus production model

Model estimating population growth and sustainable yield

Maximum sustainable yield (MSY)

Largest catch that can be taken without depleting the stock. MSY = (rK)/4 where r = growth rate and K = carrying capacity

Schaefer model

used to describe yield vs fishing pressure. Y = aE - bE², shows yield increases than decreases with effort. peak = MSY point

Stock-recruitment relationship

Relationship between spawning stock and new recruits

Virtual population analysis (VPA)

Method to estimate past population sizes using catch data

Yield-per-recruit model

Model assessing yield relative to fishing pressure per recruit

F0.1

Fishing mortality rate where the slope of the yield-per-recruit curve is reduced to 10% of its value at the origin; used as a conservative harvest target because yield increases begin to slow significantly.

Ecosystem-based fisheries management

Approach considering entire ecosystem rather than single species

Bottom trawling

Fishing method that drags nets along the seafloor

Swept area ratio (SAR)

Proportion of seafloor disturbed by trawling

Bycatch

Non-target species caught during fishing

Overfishing

When fishing mortality exceeds sustainable levels

Overfished stock

Stock size below sustainable threshold

Reference points

Benchmarks (e.g., BMSY, FMSY) used for management decisions

Total allowable catch (TAC)

Maximum catch allowed in a fishery

Individual transferable quotas (ITQ)

Catch shares that can be traded among fishers

Effort quota

Limits on fishing effort rather than catch

Co-management

Shared management between authorities and stakeholders

Management strategy evaluation (MSE)

Simulation approach to test management strategies under uncertainty

Observation error

Inaccuracy in collected data

Process error

Variability in natural population processes

Implementation uncertainty

Differences between planned and actual management outcomes

Magnuson-Stevens Act

U.S. law governing marine fisheries management

Annual catch limit (ACL)

Science-based limit preventing overfishing

Accountability measures (AM)

Mechanisms to enforce catch limits

Fishery management plan (FMP)

Document outlining regulations and strategies for a fishery

Essential fish habitat

Critical areas necessary for fish survival and reproduction

Bycatch minimization

Requirement to reduce unintended catch and mortality

Logistic growth curve

S-shaped population growth model where growth slows as population approaches carrying capacity (K)

MSY curve

Relationship showing maximum sustainable yield occurs at intermediate fishing pressure

Schaefer model curve

Logistic surplus production model showing dome-shaped yield vs fishing effort relationship

Fishing effort vs CPUE trend

Relationship used to estimate abundance; often declines as effort increases

CPUE hyperstability

When CPUE remains high despite declining abundance due to fish aggregation or behavior

CPUE hyperdepletion

When CPUE declines faster than actual abundance due to fish dispersion or behavior

Stock-recruitment curve

Relationship between spawning stock size and number of new recruits produced

Beverton-Holt model

Stock–recruitment model where recruitment increases with spawning stock and then levels off at high stock sizes (density dependence but no crash). R = (aS)/(1+bS). r = recruitment, S = spawning stock, a = productivity at low stock, b = density dependence strength

Ricker model

Stock–recruitment model where recruitment increases at low stock but decreases at high stock due to overcrowding or competition. R = aSe^-bS. Low S = more spawners = more recruits, High S = too many fish → competition → fewer recruits

Yield-per-recruit curve

Graph showing yield increases then decreases with fishing mortality (F)

Fmax

Point where yield per recruit is maximized

Trophic cascade graph

Shows changes in ecosystem structure when top predators are removed

Fishing down food web trend

Graph showing decline in mean trophic level of catches over time

Swept area ratio map

Spatial representation of fishing intensity and seabed disturbance

Length-frequency distribution

Graph showing size structure of a fish population used for stock assessment; used to infer age classes, recruitment, and fishing pressure

Catch curve analysis

Plot of log abundance vs age used to estimate mortality (Z)

Logbooks

Fisher-reported catch and effort records with broad spatial coverage but lower data quality than observer data

On-board observers

Fisheries-dependent data collectors onboard vessels; best source for bycatch and discard information but expensive

Depletion methods

Methods estimating population abundance from declining catch rates during fishing

CPUE standardization

Statistical adjustment of CPUE data to account for factors like gear, vessel, season, and location

Generalized linear model (GLM)

Statistical model allowing non-normal distributions and link functions; commonly used to standardize CPUE

Reasons CPUE may not reflect abundance

Fish aggregation, fisher behavior, improved technology, local depletion, and efficient searching can distort CPUE trends

Components of stock assessment

Model, data, and estimator used together to evaluate stock status