Fisheries Management, Marine Ecology, and Overfishing

Comprehensive practice flashcards defining foundational terms, management metrics, harvesting gears, and socio-economic concepts related to global fisheries.

Catch per unit effort (CPUE)

Catch divided by fishing effort; serves as a rough index of fish abundance, where falling CPUE signals declining biomass.

Maximum sustainable yield (MSY)

The largest average catch a fish stock can support indefinitely without compromising future extraction; in simple theoretical models, this occurs at about $50\%$ of unfished biomass.

Overfished

A biological state in which a fish stock is depleted to levels below its most productive threshold because fish have been caught faster than the population can reproduce.

Overfishing

An ongoing process or catch rate that is too high, removing fish faster than the population can replenish itself through reproduction.

Fish stock

A subpopulation of fish managed and assessed as a single biological unit.

Stock assessment

A model-based scientific estimate of the size, productivity, and health status of a fish stock.

Catch

The total volume or quantity of fish extracted from the water, which includes retained landings, discards, and unreported catches.

Landings

The portion of caught fish that is officially brought ashore, excluding discards and unreported fish.

Bycatch

Non-target marine organisms captured unintentionally alongside the target species, which may either be kept or discarded.

Discards

Portions of a commercial fishing catch thrown back into the ocean (alive or dead), often due to lack of market value, regulatory limits, or damage.

Harmful subsidies

Government economic support that expands fishing capacity and effort beyond sustainable thresholds, including fuel subsidies, vessel modernization loans, and gear tax exemptions.

Beneficial subsidies

Government investments that support fishery conservation and capacity reduction, such as research, stock assessments, enforcement, retraining programs, and vessel buyback programs.

Ecosystem-based management

A holistic fisheries management approach that considers the broader ecosystem (including predators, prey, habitat integrity, and human factors) rather than regulating a single target species in isolation.

Trophic level

The specific position an organism occupies within an ecological food web.

Fishing down

The serial depletion of top, high-trophic-level marine predators (such as tuna and cod), causing fishing pressure and catches to shift downward toward smaller forage fish and invertebrates.

Marine Trophic Index (MTI)

The average trophic level of landed fish catch; a persistent downward trend in MTI over time indicates the signature of 'fishing down.'

IUU fishing

Illegal, Unreported, and Unregulated fishing operations that bypass national or international fisheries governance and management rules.

Distant-water fleets

Industrial fishing fleets that operate far beyond the territorial waters or exclusive economic zones of their home countries, frequently fishing the high seas or developing countries' waters.

Fisheries collapse (Worm et al. definition)

A condition in which annual commercial fish landings fall below $10\%$ of their recorded peak catch.

Fisheries collapse (Edgar et al. definition)

A condition in which the estimated remaining biomass of a fish stock falls below $10\%$ of its historical maximum biomass.

Social trap

A collective dilemma wherein rational short-term individual decisions produce unintended, detrimental long-term outcomes for everyone, including the individuals themselves.

Collective action problem (CAP)

A situation where all participants would benefit from collective cooperation (such as harvest restraint), but individual incentives lead everyone to act competitively, producing a suboptimal outcome.

Precautionary principle

The principle stating that society should implement protective measures when there is a risk of severe or irreversible damage, even in the absence of full scientific certainty.

Maximally sustainably fished

The optimal state where a fishery harvests at the maximum sustainable yield without depleting the fish population below its most productive level.

Underfished

A status where fishing mortality is lower than the biological reproduction rate, meaning more fish could be extracted without compromising stock productivity.

Spawning stock biomass (SSB)

The total weight of mature females in a fish population, tracked in stock assessments because reproductive output depends directly on female biomass rather than total population headcount.

Sequential hermaphroditism

A life-history trait in fish (such as groupers and wrasses) where individuals change sex as they grow, meaning size-selective fishing of the largest individuals can inadvertently eliminate nearly all males.

Landing obligation

A regulatory ban on discarding fish at sea requiring fishers to retain, bring ashore, and record all catches against their allowable quotas.

Aquaculture

The farming and controlled cultivation of aquatic organisms, including finfish, molluscs, crustaceans, and aquatic plants.

Capture fisheries

The extraction and landing of wild aquatic organisms for commercial, industrial, recreational, or subsistence purposes.

Individual Transferable Quota (ITQ)

A fishery management system that assigns individual fishers or companies secure, transferable shares of a stock's total allowable catch.

Exclusive Economic Zone (EEZ)

A maritime area prescribed by the UN Convention on the Law of the Sea, extending up to $200$ nautical miles from a country's coastline, over which the coastal state exercises sovereign rights to marine resources.

Ministerial discretion

Legal provisions (such as in Canada and the European Union) that permit government ministers to set commercial fishing quotas above the levels recommended by scientific stock assessments.

Pole and line

A small-scale, highly selective fishing method used to catch large pelagic fish like tuna one at a time using surface baitfish, resulting in minimal bycatch.

Purse seine

A large vertical net deployed to surround dense schools of pelagic fish, after which the bottom of the net is drawn closed like a drawstring purse.

Bottom trawl

A heavy cone-shaped net dragged across or just above the seabed, known for high catch rates but significant bycatch and substantial physical destruction of benthic habitats.

Pelagic trawl

A cone-shaped net pulled through midwater zones using acoustic sonar systems to locate fish, operating without direct contact with the seafloor.

Gillnet

A vertical wall of netting suspended in the water column that traps passing fish behind the gills based on mesh size, which can generate high non-target bycatch.

Longline

A fishing line trailed behind a vessel with baited hooks attached at regular intervals, used in pelagic or demersal waters and associated with accidental hookings of seabirds and sharks.

Dredging

A fishing technique using a rigid metal frame dragged across the sea floor to scrape up burrowed bivalves (scallops, clams, oysters), causing severe physical disturbance to benthic sediments.

Pots and traps

Enclosed wood, wire, or plastic containers with cone-shaped entrances placed on the seabed for roughly $24$ hours to capture crabs and lobsters.

Driftnets

Extensive floating nets historically deployed up to $60\,\text{km}$ in length ('curtains of death') before the United Nations General Assembly capped them at $2.5\,\text{km}$ in 1991.

Ghost fishing

The continued, unmonitored trapping and mortality of marine animals caused by lost, abandoned, or discarded fishing gear.

1992 Newfoundland Cod Moratorium

The Canadian government's emergency declaration halting the East Coast Newfoundland Atlantic cod fishery after stock collapse, which eliminated roughly $37{,}000$ jobs.