- Slides: 14
Humans and the Sea -Fisheries, management, and sampling • Millions of people depend on fisheries… in what ways? – Food • 86 million tons/year – Jobs – Products & materials – Recreation & entertainment • Sport fishing • Diving & tourism • Aquarium trade
Fig. 17. 2 Lots of people in the world… and, like other natural predator/prey relationships, we take advantage and harvest many marine organisms …thus, competition for resources Marine ecosystems provide over 30% of worldwide animal protein consumption How much is this?
Are these levels sustainable? How do we prevent overfishing? – Depends on what, where, and current practices
…stresses on fisheries – What is the 2010 demand for fish? • 10 -40 million tons above production • Cultural practices, consumption, etc. , varies worldwide – E. g. average fish consumption/person/year • Japan = 37. 7 lbs • U. S. = 16. 6 lbs
• Where are the richest fishing grounds? – Areas of upwelling, bordering continental shelf where primary production is higher • Most of the largest takes are around industrial nations – Exploited for the longest time • Most fishing grounds in Atlantic, Pacific, Mediterranean are in decline or exhausted Why and How is this happening? Fig. 17. 4
Fig. 17. 6 • Gill net: Northeast and worldwide – panel of webbing of clear monofilament line; can be set at any depth; fish can’t see the net, so they swim right into it and are caught. – Lots of bycatch (“junk”/non-target) -animals that are too large to pass through the webbing (mammals, turtles, etc. ) • Purse seines: – Vertical, weighted net encircling aggregates; pulls bottom closed (drawstring) preventing fish from swimming down – Unintended bycatch; i. e. dolphin, sharks, sea turtles • Hook and line, and long-line: – Commercial rigs can setup miles of unselective longlines (lots of bycatch) – hard to be selective with this gear…but, possible. E. g. , choosing bait, jigs, lures, and hook sizes known to catch their target species. • Trawls / Bottom trawl: single most important fishing method in the Northeast – produces the most noticeable bycatch problem & demolishes the environment – bottom trawl is a funnel-shaped net that is dragged on the bottom of the sea – Mortality: damaged in the net, brought up from the depths too quickly, or thrown back too late.
• What are the most important fish? – Schooling fish • Herring, sardines, anchovies… • Over continental shelf & upwelling areas • Caught by purse seines – Demersal cold-water fish • Cod, pollock, haddock… • E. g. Alaska pollock is largest fishery of U. S. • Caught by trawls • Over exploited; closed many fisheries in the last decade – Open-ocean fish • Tuna (skipjack, yellowfin, albacore, bigeye, bluefin) • Caught by seines, longlines, and gill nets
Can we use methods that are more sustainable and environmentally responsible? • Harpooning – Harpooners catch large, pelagic predators such as bluefin tuna and swordfish. • Hook and Line – Hook and liners target a variety of fish, ranging from open ocean swimmers, like tuna and mahi, to bottom dwellers, like cod • Trolling – Trollers catch fish that will follow a moving lure or bait, such as salmon, mahi and albacore tuna.
Fig. 17. 10 Policies, regulations, & enforcement • Balance between population size, natural mortality, and fisheries Sustainable? # of fish caught ≤ # fish reproduced • Use sustainable fishing methods (globally, change our ways) to prevent population / fisheries collapse
Example of sustainable commercial fishery • http: //www. youtube. com/watch? v=i 5 m. MI 8 t 7 v. V 0&feature=related
Research and Restoration provides evidence/data to inform regulations
• “spaghetti” tags • Archival tags • Satellite tags • Acoustic telemetry
Fig. 17. 12 • Mariculture / Aquaculture – Farming • Open vs. closed • Pros vs. Cons – High production at expense to environment; ie, wild populations, disease, pollution, etc. – Use of genetics & biotech • Faster growth, disease resistance, etc. – Salmon, shrimp • Local sustainable mariculture – www. carlsbadaquafarm. com • Local restoration projects – http: //www. pier. org
Human Impacts – our role, impacts, and responsibilities • Habitat destruction – – Fisheries Resource management Recreation Aquaculture • Pollution – Coastal runoff – Sewage – Oil • Introduced species – Invasive / pest species What can we do instead? • MPA – Marine Protected Areas • Know our impacts and respect that we are just one species of nature • Be an informed consumer • Reduce, reuse, recycle