Over Fishing Oceans 11

What is “fishing”? Exploitation of marine organisms for sustenance, profit, or fun. Examples: Fish- cod, halibut, salmon, redfish, stripped bass… Shellfish Mollusks- clams, scallops, oysters, abalone… Crustaceans- crabs, shrimp, lobster… Reptiles- turtles Mammals- whales

Why do we fish? Survival- many costal communities, particularly in developing countries, fish as a primary food source. Recreation- fishing for fun. Profit- commercial exploitation as a means of earning a livelihood.

What are some of the effects of fishing on humans? Sociology- in some places people need to fish to survive, in many others they simply want to fish as a mode of recreation. Economics- individuals and regions can be dependent on fishing as a source of income. Ecology- natural systems are easily disrupted by fishing.

What is “over fishing”? Removal of organisms from the marine environment by humans at a rate which cannot be sustained by the local ecosystem and therefore significantly alters natural ecosystem. or Fishing a population faster than it can replace itself; the population decreases in size as a result.

How big is the problem? The world marine catch is nearly 100 million tonnes per year. 27 millon tonnes of by-catch (almost 1/3 of total catch) is thrown back dead into the ocean Larger shrimps fetch a higher price, there is an incentive for discarding smaller fish as shown left.

What are some consequences of over fishing? Much more complicated than reduction of one species Trophic interactions Examples: Salmon, killer whale, sea otter Change in ecosystem structure Loss of biodiversity

Consequences…By - Catch! By-catch is all non-target species caught with target species whether retained then sold or discarded One example of by-catch is dolphins caught in tuna nets. Often a problem with widespread use of unselective fishing gear Bottom trawling disturbs everything on the ocean floor

Collapse of the North Atlantic Cod Fishery Canadian cod stock severely depleted by local and distant water fleets Canada declared Extended Fisheries Jurisdiction in 1979 to control and rebuild the fishery Expected a rise in Total Allowable Catch (TAC) by 1985 Instead the fishery continued to decline and effectively closed in 1992

What Happen? Mismanagement? Fishing mortality exceeded sustainable level estimates Stocks never achieved 50% of predicted total allowable catch Canadian fleet over harvested cod

How? Upper limit was used to calculate harvest quota every year When upper limit became insufficient to economically support fishery quota was increased Short term economic gain won out over biology

The Irony Biologists could see the catastrophe happening and were powerless to stop it Long term economic loss (closure of fishery) far outweighs short term benefit Economy loses more

Facts on file science online

Now what? How can we fish only to an extent which does not significantly alter it and the natural system in which it occurs? Widely varying degrees of opinion.

Problems Estimating populations Estimating catch Predicting population change based on… catch. environmental statistics limited knowledge of life history. Tends to err on the side of over harvest Doesn’t always consider ecology

Some Solutions: Marine Protected Areas Effective if: Large enough Protect source populations Effectively enforced Currently well below 1% of marine systems are protected by MPA’s

Legislation Through regulation and laws control the total allowable catch Effective regulation should be consistent with biology International Compliance

Responsible Recreation Increasing evidence suggests impacts of recreational fishing

Conclusions Conservation of marine fisheries impacts peoples livelihoods, survival, and recreation. It influences the marine and terrestrial environments. It is everyone's responsibility.

Case Study: The Impact of Overfishing Case Study: The Impact of Overfishing ***Please put all answers on looseleaf! Vocab: list the definition of the following fishstock, net growth rate, MSY, TAC, OSY Do case study but omit “l” and “m” Do only question #2 from Questions for Application and Further Research