Dynamic Changes in Marine Ecosystems Fishing, Food Webs, and Future Options (2006) / Chapter Skim
Currently Skimming:
3 Considering the Management Implications
3 Considering the Management Implications
Pages 59-76
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 59... ...
To move beyond managing for individual fishery yields, policies must be developed to fit within a framework of ecosystem-based management -- considering the fishing effects of food-web interactions, bycatch, and habitat. Because all organisms are linked within a system, management strategies will have to make explicit tradeoffs among fished stocks, whether it is setting harvest rates, rebuilding strategies, or promoting other uses.
|
From page 60... ...
These issues are addressed in Chapter 4. FISHERIES MANAGEMENT IMPLICATIONS OF ECOSYSTEM INTERACTIONS The consideration of multi-species interactions requires making decisions that involve explicit allocation tradeoffs both between food-web components and between user groups.
|
From page 61... ...
Setting the harvesting strategy for such a connected system would require the total allowable harvest to be divided between humans and the predators of the target species with total takes low enough that the population of the target species does not collapse. While these principles are straightforward in the abstract, in practice setting "single-species" harvest targets that take these ecosystem effects into account will be complex.
|
From page 62... ...
Fishing Multiple Trophic Levels Managing fisheries that target multiple levels of the food web presents a more complex challenge than fishing one pair of predator and prey species. Adding lower trophic levels to the catch means that both predators and groups of prey are targeted.
|
From page 63... ...
As discussed previously, exploitation of lower trophic levels creates competition between humans and apex predators for a common prey, but one in which the reduction in apex predators may allow greater catches of the prey species by the fishery than if only the prey species were harvested. But, reductions in fishing pressure on some of the larger predators would increase predation on the lower trophic levels and would require a reduction in fishing effort on these components of the food web.
|
From page 64... ...
. If fish, seabirds, marine mammals, or sea turtles, for example, migrate along specific pathways, it might be possible to reduce overall mortality by protecting them when they are passing through or aggregating in a particular area.
|
From page 65... ...
Fishery management implications arise because fishing may amplify the effects of climate changes. How should managers anticipate and adjust fishing pressure during a climatically driven shift, especially a shift from high to low productivity?
|
From page 66... ...
. The suite of harvest targets that maximize the sum of systemwide yield would differ from their singlespecies analogues in ways that depended upon trophic interactions (e.g., Beddington and May 1977, May et al.
|
From page 67... ...
The opportunity cost associated with other ecosystem services increases with higher levels of biomass and other characteristics closer to pristine states. Additionally, when cascading effects are caused by the fisheries, even maintaining harvest rates at the single-species MSY level could mean that developing other uses is precluded.
|
From page 68... ...
However, this is only one example and clearly more such studies are needed to advise management regarding what deviations from single-species MSY would be necessary to maintain ecosystem integrity. The following section lays out a framework for evaluating fisheries management strategies in an ecosystem context, but, in the short-term and for systems where this framework cannot be implemented, a precautionary approach (e.g., Restrepo et al.
|
From page 69... ...
This is because ecosystem effects often result from the specifics of how fishing effort is exerted, rather than the absolute level of removal of target species. Habitat impacts and bycatch, for example, result from the level and type of fishing effort, regardless of how much is landed.
|
From page 70... ...
In U.S. fisheries, these output and input control decisions are vested mostly in the Regional Fishery Management Councils.
|
From page 71... ...
The first would require the specification of a new set of systemwide harvest targets that account for trophic interactions as well as rules that limit ecosystem impacts such as habitat loss and loss of biodiversity. The second step would be to determine a new suite of regulatory actions to limit effort according to the modified harvest rules.
|
From page 72... ...
, and they always involve contentious initial allocation decisions regarding who is granted privileges and how much allocation is granted. In bottom-up systems with secure access privileges, the tactical decisions are left to the fishermen about how to conduct their fishing operations to maximize the value of their allocations.
|
From page 73... ...
And "other fishermen" may include those with whom a particular group of rights holders interact via the interrelated nature of their target species. For example, in the earlier cod capelin example, cod fishermen might find it desirable to purchase harvest access privileges held by capelin fishermen to account for the predator-prey ecosystem effects of having a larger biomass of capelin to support the cod.
|
From page 74... ...
Individual agencies have mandated responsibilities that do not necessarily allow them to develop management actions that are more broadly based and coordinated across sectors of human activity. With respect to fisheries, while the MSFCMA calls for conservation of ecosystems on which fisheries depend, the national standards for management plans do not clearly call for coordination with other management actions outside the fishery sector.
|
From page 75... ...
As described in this chapter, consideration of ecosystem effects requires explicit consideration of tradeoffs in ecosystem services under different management actions. In effect, the current statutory structure precludes certain tradeoffs unless some overarching authority for ecosystem-based management is created.
|
From page 76... ...
An overarching mandate that allows explicit consideration of tradeoffs is needed to resolve the difficulties of reconciling the existing mandates.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.