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Fisheries, sustainability & conservation

Fisheries supply a valuable food resource, but are seldom managed in a sustainable manner

Fisheries and fisheries management Setting and enforcing limits Summary Related issues

Fisheries and fisheries management Setting and enforcing limits Summary Related issues

Humans have exploited many different types of resource species in the sea

Current annual fish catches total million tonnes, and provide 20% of human protein consumption

Over 100 million people depend on ocean fisheries and aquaculture for their livelihoods

Subsistence fisheries usually take relatively small amounts of fish This means that the fishery is sustainable - the fishery does not result in a long-term decline in the resource species

Modern fishing equipment means that far more fish can be caught, to supply an expanding market

About 50% of exploited fish stocks are close to their maximum biological production level

A further 25% of exploited fish stocks are over-fished

A recent study estimates that ‘industrial’ fishing has reduced the biomass of large predatory fish to 10-20% of pre-fishery values, usually within fifteen years

Fishery management should ensure that fishing does not deplete populations below sustainable levels, and should protect endangered populations

Fisheries and fisheries management Setting and enforcing limits Summary Related issues

Managing a fishery in a sustainable manner means that catches must be regulated so that the fish population remains stable This requires an understanding of the current status of the population and its biology

Population size Population age distribution Growth rate at given ages Reproductive rate at given ages Mortality rate at given ages

Fishery management is designed to ensure that the fish population does not drop below the value needed to replace caught fish

Fishery management can use various approaches to regulate a fishery

Set quotas or allowable catch levels Establish ‘no-fishing’ areas Establish a ‘closed season’ Set minimum fish size-limit, or specify net mesh size Close fishery entirely

Excluding young fish from the catch is achieved by using nets that allow small fish to escape However, fish may be injured even though they are not caught

There are several other practical problems in regulating fisheries

Illegal and unregulated fishing Inadequate scientific data Minimum size limits may not be effective in excluding under-sized fish Target species may be caught by other fisheries Natural environmental variability may make prediction unreliable

In some cases, catches of individual species may be prohibited, but there is no way to prevent them being caught Supposedly protected fish have to be discarded, even though they are already injured or dead

Finally, measures to protect fish populations may have important social and economic impacts

Fisheries and fisheries management Setting and enforcing limits Summary Related issues

Habitat damage Environmental effects of discarded gear Incidental mortality and by-catch There are several effects associated with fisheries which also give cause for concern: Ecosystem effects

Large fishing gear and dynamite-fishing cause extensive damage to coral reefs and other habitats

Discarded and lost fishing gear and other materials form a serious hazard for marine animals

Marine birds and mammals, such as dolphins, can drown in nets Long-line fishing is a significant cause of population decline for some seabirds, such as albatrosses Fishing for small species may catch young stages of larger protected species, below their minimum size Few fisheries catch only the intended species

Fishing can also compete with other species in the ecosystem Some modern fishing regulatory measures aim to maintain the entire local ecosystem in balance, rather than simply conserving target species

Fisheries and fisheries management Setting and enforcing limits Summary Related issues

Fishing is an important source of food Many fish populations have been reduced by over-fishing You have seen that -

Fishery management aims to provide a sustainable resource Various methods are used to regulate fisheries You have seen that -

NOTES for USERS The material in this slide show is designed to support the teaching of science at Key Stage 1 A full description of the slide show, and linked activities for students, can be found on the National Marine Aquarium (NMA) web-site: Teachers are free to amend the slide show in whatever way they feel fit, or to use slides in other contexts. However, please note that neither the NMA nor the designers will accept responsibility for modifications, and original material remains copyright of the NMA Individual images used in the slides are copyright of NMA or STEP, except where acknowledged separately The slides have been set up to display as A4 landscape format. If they are incorporated into other slide sequences with different display settings, change in aspect ratio and text location will occur The slide sequence contains the minimum of effects and transitions. However, there are some automated animations, and teachers will wish to make sure that they are familiar with the sequence before use in class Use the PowerPoint notes viewer to obtain additional information for some slides