test 2 Flashcards
Post-industrial revolution
Human populations increase exponentially – Steam engines allow efficient trawling – Fishing gear improvements – Huge factory ships
Post WW II
Development of sonar
• Huge industrial fleets
Food and Agricultural Organization
16.6% of global intake of animal protein (increasing)
2009 global intake of animal protein
16.6% (increasing)
Increasing demand for fish met by
aquaculture production
FAO 2010 State of World Fisheries
Most stocks fully exploited or
overexploited
Bottom fishes
overexploited
Pelagic fishes
fully exploited
Some cephalopod stocks
underexploited
Typical History of A Fisheries
Discover a new stock • Fish the heck out of it • Populations decline reducing profit • Call in the fisheries scientists • Scientists declare it is too late….
Fisheries Management Attempts to
Avoid Overfishing
Use Yield Models to manage
MSY
Maximum Sustainable Yield:
– Catch & Effort
Problems with Fisheries Management
Attempts to Avoid Overfishing
Often a single TARGET species • Stock Assessments typically on just the target species • Rarely a single catch and therefore ecosystem changes with fishing • Bycatch often discarded
Multispecies MSY
Both target and non-target species collapse with increasing exploitation rate
Gadus morhua
Atlantic cod
Complete collapse of fishery in
1990’s with loss of 2.5 billion adults
– Continued lack of recovery despite
stringent controls on the fishery
Top predators in worldwide decline
– Estimates as high as 90% in some regions
Predators typically keystone species
Impact on community disproportionate to
abundance
Antipredator behavior
Risk Effects.
Direct predation –
natural mortality
Blacktip declines
on east coast of US
Direct predation
– Risk effects
Shifting Baselines
Pauley: young scientists fail to remember what historical populations were like “Each generation accepts a baseline the stock size and species composition that occurred at the beginning of their careers.”
“Destructive fishing
-Outright habitat destruction
• Overfishing
Habitat Destructive Fishing Practices
Explosives: ‘dynamite fishing’, ‘blast fishing’ Muro-ami & Kayakas • Poisons Bottom Trawling
Inappropriate Fishing Practices
Beach Seining Large-scale pelagic fishnets/gill nets/ drift nets Tuna fisheries & dolphin/shark bycatch Shark fining: – Excessive bycatch – Push netting – Highgrading
Marine Pollution:
Almost all land origin
introduced to oceans from runoff, wind
& rain (also direct dumping of wastes)
