Lecture 7 - Fishing and Overfishing

What are the four main topics covered in the fishing and overfishing lecture?

Development of commercial fishing, global fisheries trends, the collapse of Newfoundland cod, and ecosystem effects of fishing.

How did commercial fishing change in the early 20th century?

Motorized fishing vessels allowed fishers to travel farther offshore, remain at sea longer, and catch more fish.

When did motorized fishing vessels first appear?

Early 20th century.

When did factory freezer trawlers appear on the Grand Banks?

Late 1950s.

What are factory freezer trawlers?

Large fishing vessels that can remain at sea for months and process hundreds of tonnes of fish per day.

How did modern fishing technology remove natural refuges for fish?

Larger, more advanced vessels could access offshore areas that were previously difficult or impossible to fish.

What are gill nets?

Vertical fishing nets that catch fish by entangling them, often around their gills.

What are drift nets?

Fishing nets that drift with ocean currents and entangle fish.

What are fish traps?

Structures that guide fish into enclosed areas from which they have difficulty escaping.

What is long-lining?

A fishing method using a long line with numerous baited hooks.

What is benthic long-lining?

Long-lining that targets fish living near the seafloor.

What is pelagic long-lining?

Long-lining that targets fish swimming in the water column.

What is purse seining?

A fishing method that surrounds a school of fish with a net and closes the bottom to trap them.

What is bottom trawling?

A fishing method that drags a large net across the seafloor to catch bottom-dwelling organisms.

Why are humans different from natural marine predators?

Humans use technology to catch enormous quantities of fish, travel long distances, and continue harvesting even when local populations decline.

What are the six stages in the development of a fishery?

Unexploited, fishery development, fully exploited, overexploited, collapse, and recovery.

What happens during the unexploited stage of a fishery?

Fish abundance is high, fishing effort is minimal, and catches are low.

What happens during fishery development?

Fishing fleets expand, catches increase, and fish abundance begins to decline.

What happens when a fishery becomes fully exploited?

Fishing effort and catches are high, while fish abundance has declined from its original level.

What happens during overexploitation?

Fishing pressure becomes excessive, causing fish abundance to decline further.

What happens during fishery collapse?

Fish abundance and catches decline dramatically, and fishing may become unprofitable.

What happens during fishery recovery?

Fish abundance may gradually increase after fishing pressure is reduced.

Why can fish catches increase while fish abundance decreases?

Increasing fishing effort and technological efficiency can temporarily produce higher catches despite declining fish populations.

What is the tragedy of the commons?

The overexploitation of a shared resource because individuals acting in their own self-interest have incentives to take as much as possible.

How does the tragedy of the commons apply to fishing?

Individual fishers benefit from catching more fish, but excessive harvesting by everyone depletes the shared fish population.

Why do many fisheries collapse?

The tragedy of the commons, poor management, difficulty estimating fish abundance, socioeconomic pressures, and natural population fluctuations.

Why are fish stocks difficult to manage?

Fish abundance is difficult to estimate, populations fluctuate naturally, and economic or political pressures can outweigh scientific advice.

How many people does the global seafood sector directly employ according to the lecture?

Approximately 65 million people.

How many people's livelihoods are supported by the seafood sector according to the lecture?

Approximately 600 million.

What industries are included in the seafood sector?

Fishing, aquaculture, fish processing, transportation, vessel maintenance, and related services.

What are the five leading species in global capture fisheries shown in the lecture?

Anchoveta, skipjack tuna, Alaska pollock, blue whiting, and Pacific sardine.

How much anchoveta is caught annually in the lecture's data?

Approximately 5 million tonnes.

How much skipjack tuna and Alaska pollock are caught annually in the lecture's data?

Approximately 3.6 million tonnes of each.

What percentage of global capture fisheries production comes from the five leading species shown?

Approximately 17%.

What percentage of marine fishery stocks were sustainably fished in 1974?

Approximately 90%.

What percentage of marine fishery stocks were sustainably fished in 2023?

Approximately 62.4%.

What percentage of marine fishery stocks were overfished in 2023?

Approximately 37.6%.

What is an overfished stock?

A fish stock depleted below a biologically sustainable level.

Does overfished mean that no fish remain?

No, it means the population has been reduced below a sustainable level.

What are the three stock categories shown in the global fisheries graph?

Underfished, maximally sustainably fished, and overfished.

What is a maximally sustainably fished stock?

A stock being harvested at approximately the maximum level considered biologically sustainable.

What is the overall global trend in overfished marine stocks?

The percentage of overfished stocks has increased substantially since 1974.

What are capture fisheries?

Fisheries that harvest wild fish and other aquatic organisms.

What is aquaculture?

The farming of aquatic organisms such as fish and shellfish.

How has aquaculture changed relative to capture fisheries?

Aquaculture production has grown rapidly and surpassed wild capture fisheries production.

What percentage of aquatic animal food availability came from aquaculture in 1990?

Approximately 18%.

What percentage of aquatic animal food availability came from aquaculture in 2020?

Approximately 55%.

What percentage of aquatic animal food availability is projected to come from aquaculture by 2050?

Approximately 65%.

How has global marine capture fisheries production changed since 1990?

It has remained relatively stable at approximately 80 million tonnes annually.

How much aquaculture production was recorded in 2024?

Approximately 103 million tonnes.

What has driven most of the recent increase in global seafood production?

Growth in aquaculture rather than increases in wild capture fisheries.

How have catches in temperate fishing areas changed since approximately 1990?

They have generally declined.

How have catches in upwelling fishing areas changed since approximately 1990?

They have generally declined.

How have catches in tropical fishing areas changed over the period shown?

They have generally increased.

What is catch per unit effort (CPUE)?

The amount of fish caught per standardized unit of fishing effort.

What does declining CPUE indicate?

Fishers are catching less fish relative to their fishing effort, potentially indicating declining fish abundance.

How much has fishing fleet power increased since the 1950s according to the lecture?

Approximately tenfold.

How has catch per unit effort changed since the 1950s?

It has declined to approximately 50% of its former level.

What is the main conclusion from declining catch per unit effort?

Humans are fishing much more intensively but catching proportionally less.

Why are humans considered the real top predators in marine ecosystems?

Humans remove large quantities of organisms across multiple trophic levels using highly efficient fishing technology.

What are the major ecosystem effects of fishing?

Harvest mortality, bycatch, habitat destruction, changes in predator-prey relationships, and altered ecosystem structure and function.

What species was central to the Newfoundland cod fishery?

Atlantic cod, Gadus morhua.

How long was Newfoundland cod one of the world's most productive fisheries?

Approximately 500 years.

Where was the Newfoundland cod fishery concentrated?

The Grand Banks and surrounding waters off Newfoundland and Labrador.

When did Newfoundland cod catches begin declining significantly?

During the 1970s.

What is an Exclusive Economic Zone (EEZ)?

An offshore area extending up to 200 nautical miles in which a coastal country has sovereign rights over natural resources.

How far did Canada's EEZ extend before expansion?

12 nautical miles.

How far did Canada extend its EEZ in 1977?

200 nautical miles, approximately 370 km.

Why did Canada extend its EEZ?

To gain greater control over offshore fisheries as cod catches declined.

Who caught most Newfoundland cod before the early 1970s?

Foreign fishing vessels.

Why did extending Canada's EEZ fail to prevent cod collapse?

Canada encouraged domestic fishing expansion rather than sufficiently reducing catches.

How did Canada encourage increased cod fishing after EEZ expansion?

Through financial assistance that supported larger fishing vessels and increased fishing capacity.

What happened to Newfoundland cod in the late 1980s?

Decades of overfishing caused a severe collapse in the population.

When was the Northern cod fishery closed?

1992.

How many people lost their jobs following the Northern cod fishery closure?

More than 30,000.

When did the commercial Northern cod fishery reopen?

2024, after approximately 32 years.

What was the peak historical cod catch shown in the lecture?

Approximately 810,000 tonnes.

Why did people underestimate the risk of Newfoundland cod collapse?

Cod had historically been so abundant that many believed the population could not be exhausted.

What is spawning stock biomass (SSB)?

The total biomass of mature fish capable of reproducing.

Why is spawning stock biomass important?

It represents the reproductive portion of a population responsible for producing future generations.

What happened to Northern cod spawning biomass before the collapse?

It declined dramatically as decades of fishing removed most mature adults.

What types of cod remained after decades of overfishing?

Primarily younger, less fecund fish.

What is fecundity?

An organism's reproductive capacity, often measured by the number of eggs it produces.

Why does removing mature adult fish reduce population recovery?

It reduces reproductive biomass and can leave fewer highly fecund individuals to produce offspring.

Why can fish catches be misleading indicators of stock health?

High fishing effort can maintain catches even while the underlying population declines.

Why is historical context important when evaluating cod recovery?

Recent increases in biomass may appear substantial but remain small compared with historical population levels.

What was the Northern cod fishing quota in 2024–2025?

18,000 tonnes.

What was the Northern cod fishing quota in 2025–2026?

38,000 tonnes.

What was the Northern cod fishing quota in 2026–2027?

59,000 tonnes.

What was the Northern cod quota when the fishery closed in 1992?

Approximately 160,000 tonnes.

What is the Limit Reference Point (LRP)?

The lower stock biomass boundary that fisheries management aims to avoid crossing.

What is the Upper Stock Reference (USR)?

A biomass boundary above which a fish stock is classified as healthy under the management framework shown.

What has happened to Northern cod spawning biomass in recent years?

It has increased and recently crossed the Upper Stock Reference.

Why is there pressure to increase Northern cod fishing quotas?

Recovering spawning biomass has encouraged calls for greater commercial harvesting.

What is the concern with increasing cod quotas too quickly?

Increased fishing pressure could jeopardize recovery and potentially contribute to another population decline.

What happened to Newfoundland snow crab catches after the cod moratorium?

Catches increased substantially.

What happened to Newfoundland snow crab stock size despite high catches?

Stock size declined substantially over the period shown.

What lesson does the Newfoundland snow crab example illustrate?

High catches do not necessarily indicate a healthy fish population, and overexploitation remains a concern.

Why are collapsed fish populations often slow to recover?

Reproductive adults have been depleted, fish need time to mature, and environmental conditions and food-web changes can limit recovery.

How quickly was Northern cod initially predicted to recover?

Approximately two years.