Fisheries Flashcards
Features of industrial fisheries?
Diverse target species.
Single species operations (eg: Peruvian anchovy fishery) vs multispecies/nation fisheries (eg: North Sea fishery).
Continental shelf = most productive area.
High mechanisation = capital intensive.
Environmental concerns w/ industrial fishing?
Overexploitation of target species.
Bycatch of non-target species.
Damage host ecosystems.
Fishery production statistics?
Capture fishery increased until 1980s, then levelled off.
Aquaculture fishing increased since 1980s.
Global fisheries produce 20kg fish per capita. 50% produced by wild fisheries.
4.6 million ships, 1/3 decked, 2/3 undecked.
80% motorised fishing vessels in Asia. Europe = 3%. Africa = lowest.
Overfishing statistics?
1970s: 40% stocks underfished, 10% overfished.
Now, more stocks overfished + fewer stocks underfished.
Max sustainably fished stocks increased slightly, but not in proportion = too much overfishing.
Mediterranean + Black Sea = least sustainably fished. Pacific = most sustainably fished.
Atlantic: Alarming that it’s so unsustainably fished, because surrounded by nations w/ knowledge.
Fishing trade flows?
Europe imports 39%, keeps 61% for internal trade.
Oceania imports 88% (69% from Asia) + keeps 12% for internal trade.
Fishing classifications?
Demersal vs pelagic.
Active vs passive.
Target species: roundfish - cod, flatfish - sole, whitefish - hake.
Depth: Inshore (200m deep, 6 nautical miles out), pelagic (tuna + mackerel), + deep-water (orange roughy).
Trawling?
Demersal + pelagic fishing.
Variations: Side, stern, beam, otter, mid-water.
Bottom trawl: Prawns, flat fish, round fish.
Catch high-value fish (eg: monkfish, rays, flatfish).
Impacts of trawling?
Destroy seabed (levels). Low selectivity = high bycatch. Energy-demanding (esp bottom trawling).
Netting?
Floats on top, lead rope on bottom. Can adjust height.
Selectivity: Opening size + strength.
Variations: Set (static), encircling, seine, purse seining (sardines, herring), + trammel-gill.
Fish aggregation devices (but issues w/ bycatch).
Large spring tides collapse nets. Neap tides = max time w/ net extended.
Trolling?
Outrigger arms w/ baited lines.
Selective = low bycatch.
Used for mackerel + tuna.
Longlining?
Many km long, set w/ baited hooks, soaked for hours.
Monofilament mainline attached to drum/reel.
Potting/creels?
Crabs/lobsters.
Selective (pot neck width, mesh width, escape doors, min body size).
V-notch young/female crabs = can’t be sold until moulted.
Baited pots soak for 2-3 days (avoid cannibalism).
Stock assessments?
Estimate current + future fish stocks.
- Inform management plans.
- Fishing pressure scenarios.
- Inform annual quotas.
- Long-term fleet management prevents fleet decommissions (expensive + job losses).
Issues: Can’t count all fish, fish move, + recruitment variability.
Max sustainable yield?
Catch made in a yr w/o endangering future capacity.
EU goal = MSY, but most stocks still overfished.
Fishery management values?
Fishing mortality (F): Proportion of fish stock taken each yr by fishing.
Spawning stock biomass (SSB): Minimum adult pop needed for sustainable pop. MSY achieved when fishing mortality doesn’t exceed SSB.
Recruitment: No. of young fish produced that survive to adulthood.
Fish landings: Fish tonnage landed in markets.
EU fish stocks?
58% commercial stocks not in Good Environmental Status.
Only 12% in GES for both fishing mortality + reproductive capacity.
Regional differences (Mediterranean + Black Sea poorly assessed).
Remains largely unsustainable, but improving in NE Atlantic + Baltic.
Estimating fish abundance?
Fish landed at port.
Fishing activities at sea.
Landing data; Total catch, body length, age, + breeding health.
Research vessel surveys.
EU member states coordinated by International Council for Exploration of Seas.
England + Wales = Cefas. Scotland = Marine Scotland.
Calculating fish age?
Otoliths.
Lack of young fish = poor spawning.
Lack of older fish = overfishing.
Data from fishermen?
Discards at sea.
Catch per unit effort.
Perception data.
Tagging.
Research vessel surveys?
Cross-check + validate fish landings.
Hydroacoustic biomass surveys (non-invasive) + plankton surveys.
Fish tag + release (fish movement, preferred habitat, lifespan, catchability).
Tag manufacturers (eg: Cefas, Vemco, Wildlife Computers).
Fish egg + larvae surveys?
Relationship between no. of eggs + no. of adults. CPR Survey (1936, Alistair Hardy) = fish stock estimation.
Acoustic surveys?
Used for pelagic fish stocks (eg: herring, sardines).
Eg: Towed Fisheries Acoustic Systems.
Worm et al (2006).
Declining diversity = Resource collapse, + decreased recovery potential, productivity, stability, + water quality.
Biodiversity loss impaired critical ecosystem services:
- 33% viable fishery decline.
- 69% nursery habitat decline.
- 63% filtering/detoxification service decline.
Rate of fishery collapse increasing - 29% currently-fished species considered collapsed in 2003.
Global collapse of currently-fished species predicted by mid-21st century.
Sumaila et al (2012).
Rebuilding fisheries = increase profits $600 billion to $1400 billion in 50yrs.
Rebuilding would cost $203 billion.
Benefits would exceed costs 12yrs after rebuilding.
Negative impacts of fish stock collapse seen in northern cod collapse off Newfoundland.
