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Bill,

A lot of trawl fisheries already leave the largest fish uncaught --  
and receive a lot of negative publicity for doing so. The "domed  
partial recruitment" arises (primarily but not exclusively) because  
many fish species have distributions somewhat segregated by size.  
Trawl fisheries tend to concentrate where the highest tonnages can be  
taken in the least time, which is not in the areas frequented by  
scarce, large fish. It might well be worth enhancing that trend  
towards lower fishing mortalities at higher ages but only if enough  
individuals escape the fishing pressure of the intermediate ages, so  
that there are big fish to not catch.

As David Kerstetter noted, it should be possible to develop sorting  
grids that would release larger fish, while retaining mid-sized ones.  
However, persuading people that that is the way to go wouldn't be  
easy. In most fisheries that I encounter, public debates over  
conservation strategies don't seem able to progress beyond the absurd  
oversimplification that we just need to let each fish spawn once  
before it gets caught. There is often strong pressure to push minimum  
sizes ever higher.


Trevor Kenchington



On 17-Apr-08, at 7:40 AM, Bill Silvert wrote:
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>
> The examples that David gives are mainly from fisheries where the  
> catch is handled one by one, as in the recreational fishery or hook  
> and line fisheries. I imagine that these are relatively easy to  
> control, at least in principle. My concern is more with bulk  
> fisheries, especially trawl fisheries, where by the time the fish  
> come on board they are either dead or so stressed that they are  
> unlikely to survive even if immediately thrown back. Think of the  
> gadoids or small pelagics.
>
> Bill Silvert

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