Transcript Global Fisheries & Sustainability

Cait Nelson & Stephanie Avery-Gomm
Oct 22 2010
Introduction
 Technological Advances of Fishing Fleets
 No Refugia = Can’t Run, Can’t Hide
 Resource Depletion
 Catch per Unit Effort Maintained
 Models are based on data that is imprecise and error prone
 Fishing Down; Removal of large long lived fish
 Food webs are altered, lack buffering capacity
 Reverse Trends; Reduction of Fleet, Increased Regs
 Solutions…Reduce Pressure on Fisheries
Maximum Sustainable Yield
management of single species stocks
 The largest yield (or catch) over an indefinite period
 At intermediate population densities individuals are able to
breed to their maximum rate
 Surplus of individuals that can be harvested
 Growth rate of the population is at max due to the
large number reproducing individuals
Figure 1. Maximum sustainable yield occurs not at the
maximum population level, but rather at a lower, optimal
population level.
Maximum Sustainable Yield
Approach has been criticized as ignoring
several key factors involved in fisheries
management
What might some of these key factors be?
Fishing Down Marine Food Webs
 Mean TL of fished species declined from 1950- 1994
 Gradual transition in landings from long-lived, high
trophic level, piscivorous bottom fish toward short-lived,
low trophic level invertebrates and planktivorous pelagic
fish.
 Fishing down food webs leads at first to increasing
catches, then to a phase transition associated with
stagnating or declining catches.
Fishing Down Marine Food Webs
Fishing Down Marine Food Webs
Discussion
 What effects might overexploitation of top trophic
levels have on species and ecosystems?
 What other effects may FDMFW have?
Other effects of FDMFW
Trophic cascade examples
What are the solutions to achieve
sustainable fisheries?
Solutions to achieve sustainable fisheries?
Aquaculture
 Bridge the gap between
supply and demand
 Reduce pressure on wild
populations
Aquaculture Discussion
Why might aquaculture not help to reduce fishing
pressure?
Solutions to achieve sustainable fisheries?
No take zones
 NTZ protect
populations by creating
reserves for sedentary
species
What other solutions exist?
What other solutions exist?
Marine Protected Areas
 Have been shown to have positive effects in rebuild depleted stocks of
sedentary species.
NTZ
What other solutions exist?
Consumer driven choices
 Consumer driven choices to avoid unsustainably fished
stocks and endangered species
 Eg. Eco-labeling
What other solutions exist?
Consumer driven choices
Ocean Wise simplifies eating seafood sustainably
Towards Sustainability
or
Rebuilding Fisheries?