Wednesday, May 06, 2009

Invasion of the spiny dogfish

Invasion of the spiny dogfish. It doesn't sound too bad, having a few dogfish around, but wait until you hear what's happening. It's worse than ocean zombies...

Or is it? Spiny dogfish are getting blamed for ruining fishing, when New England fishermen have been doing a good job of ruining fishing themselves. Catching too much of many fish...even catching too many dogfish. Now they're blaming the victim? Check here for the rest of the story.

Now, back to the dogfish zombie invader doomsday warning...
A plague of spiny dogfish (Squalus acanthias) is interfering with fisheries in coastal states from Maine to North Carolina. Unprecedented numbers of these voracious predators are clogging nets, stealing bait and ruining the catch in fishery after fishery, needlessly penalizing the affected fishermen and coastal fishing communities. In addition to this direct interference with other fisheries, dogfish are eating vast quantities of much more valuable species, negating the effects of drastic management-mandated fishing effort reductions in those fisheries. Fishermen are sacrificing to conserve extremely important recreational and commercial species and their efforts are doing little more than providing more food for an ever-increasing population of dogfish.

How have we gotten to this sorry state? How have we let a low value species like the spiny dogfish become so plentiful that it is standing in the way of the successful rebuilding of other, far more valuable species and costing the coastal economies of a dozen states tens of millions of dollars? The simple answer is that’s what federal law requires.

OK, in case you haven't figured it out yet, blogfish thinks this is a bunch of hooey. But go ahead and decide for yourself, it's a free country.


xpend83 said...

Over the last decade or so, fisheries managers and other people and organizations responsible for natural resource management have been talking about using an "ecosystem approach." E.g. from the US Fish & Wildlife site (
"The U.S. Fish and Wildlife Service has adopted an ecosystem approach to conservation because we can't just look at a single animal, species, or piece of land in isolation from all that is around it."

Interestingly enough, neither this blog, nor any of the articles it linked to used the word "ecosystem" nor described the problem in ecosystem terms. The contention was still framed in terms of specific species. When will we move beyond tripping over our own feet and get to the problem-solving part?

Mark Powell said...

Be careful what you wish for, xpend 83. Ecosystem management is NOT killinlg a species that we don't like because it interferes with commerce.

Not sure if that's what you were getting at, but it's what the dogfish haters want when they pretend to push ecosystem management.

If I'm wrong about where you're coming from, then tell me what you hope to gain from putting dogfish in an ecosystem context if it's not a program to kill more dogfish.

Anyway, regarding ecosystems and dogfish...we're learning that predators like dogfish play an important role in structuring ecosystems, and predator extermination to reduce perceived competition for valuable species is a discredited practice from the pre-1950s era. Aldo Leopold dismantled it in his discussion of wolves and his early work killing them.

We can talk about ecosystem management of large fish off New England only after fishermen quit killing fish beyond sustainable limits. Serial overfishing has so distorted the ecosystem that it's hard to draw conclusions about species abundance and interactions.

The FIRST essential step in ecosystem management is to stop killing fish beyond sustainable limits. Duh.

Dogfish haters talking ecosystem management is like an alcoholic talking about the health benefits of moderate wine consumption. We all know what's really going on.

Ed said...

Well,one thing for sure Mr. Powell, is the ecosystem is always changing and adapting, constantly working for natural balance.

In the case of the spiny dogfish, I have seen this here on the West coast and it preceded an influx of larger sharks who will predate on these smaller sharks. Kind of like locusts before the seagulls come and get them.

As far as humans pretending they know how things "should be", well, let's just say, we try.

Ecosystem management to achieve sustainable fisheries is a sound approach if the entire ecosystem is considered and portions are not put into exclusion zones such as "no take" reserves. The reason I say this is because, in order to manage ecosystems, we cannot divide or portion the "system". This approach will cause massive shift of effort and disproportionate impacts to species outside of MPA's.

We will have to depend on MPA's to provide all the recruitment for a given geography. This is troubling when you consider genetic variability will be effected when there is little or no genetic mixing because genetic variability is sourced from a specific location.

Claims of larval dispersal are only theoretical and realistically can only occur in limited geographies and during limited seasonal wind patterns. Any change in these patterns will have more negative impact to the ecosystem than if an entire ecogeography, new word, were managed equally.