The fish skeptics

[n2doc]

The fish skeptics
Posted by Enric Sala of National Geographic May 5, 2011


In the last decade, studies analyzing global fisheries statistics since 1950 have shown a decline in marine fish catches. Most experts believe that the decline in catches is due to overexploitation, that is, we have removed fish out of the sea faster than they can replenish. Projections of trends since 1950 suggest a continued depletion of fish and consequent collapse of fisheries.



Time series of the composition of global marine fisheries catch according to the status of the stocks making up that catch, 1950−2003 (From Pauly, D. 2007. AMBIO 36(4):290-295)


However, a handful of fisheries scientists have argued recently that these studies exaggerate the problem and that most fish stocks are actually stable or rebounding (see recent blog in New York Times). Their message is that the world is mostly fine and that no significant action is required to turn things around. Based on existing evidence, most marine biologists believe that they are wrong. Most fishermen around the world will also agree that we have a real problem.

Why are the skeptics wrong? Mainly because they are showing new ‘global’ trends that suggest stability by using only data from a subset of the world’s fisheries – mostly those that are well managed and monitored, and which are doing better than most other fisheries. I agree that well managed fisheries can rebound, but these represent less than a tenth of the world’s fisheries. Who would agree on the results of a study describing the wealth of Americans using only Forbes’ millionaires list?
http://newswatch.nationalgeographic.com/2011/05/05/the-fish-skeptics/

[Gregorian]

1. This has nothing to do with human population. The planet can sustain billions more.

Don't worry. And do not make the connection. And don't be responsible.

Or maybe this is just the way it was supposed to happen, and I'm wasting my energy wishing for Ray Miland to come back to life, and do a remake of The Uninvited.

[hatrack]

2. You don't work for Fisheries & Oceans Canada, do you?

:hi:

[Gregorian]

4. I don't get it.

Honestly, I don't understand your post.

[hatrack]

5. It was sarcasm - but not aimed at you.

Fisheries Canada are the guys who utterly botched every possible call on the Grand Banks cod, in a process that went on for decades until (surprise!) there was nothing left to fish.

[kristopher]

3. Fisheries vs populations of fish species

"Projections of trends since 1950 suggest a continued depletion of fish and consequent collapse of fisheries."

This sentence from the article demonstrates that there are two separate events under discussion; and the distinction needs to be clarified since the article leaves someone not familiar with specific terms to think the discussion is about species extinction.

Definitions of fisheries on the Web:
Generally, a fishery is an entity engaged in raising and/or harvesting fish, which is determined by some authority to be a fishery. ...
en.wikipedia.org/wiki/Fisheries

fishery - a workplace where fish are caught and processed and sold
wordnetweb.princeton.edu/perl/webwn

fishery - the catching, processing and marketing of fish, shellfish etc; a place where fish etc are caught or processed; a fishing company
en.wiktionary.org/wiki/fishery

With that defined, the claim of the article becomes more clear - in general, it is the human impact on food production that is the problem under discussion, not species extinction. Extinction can occur when populations are stressed by fisheries and then they experience another stressor, such as reduced habitat in the areas where spawning occurs. However, that is a relatively rare event and does not underpin the discussion that the OP is pointing towards.

The collapse of a fishery is an economic problem brought about by poor policies controlling the way fishers enter and exit the market based on traditional market signals and the way the resource is exploited by a multinational, unable-to-be-regulated group of profit seekers. When a profit opportunity develops resources are shifted to exploit the fish involved. Without regulation that results in a boom and bust cycle of investment with consequent damaging effects on wildlife populations and human fishing communities alike when the fish "disappear" from the nets.

However, the level at which the bust occurs is usually well above that where most teleost populations (r-selected species) are at risk of extinction from that specific threat. I say "most" because there are some species, particularly those living among coral IIRC, that are able to be fished to extinction.

r- versus K-selected Species

K-selected species usually live near the carrying capacity of their environment. Their numbers are controlled by the availability of resources. In other words, they are a density dependent species. Food availability is one resource that controls population size.

K-selected species have attributes that distinguish them from r-selected species. The attributes of a K-selected species include a long maturation time, breeding relatively late in life, a long lifespan, producing relatively few offspring, large newborn offspring, low mortality rates of young, and extensive parental care. Examples of a K-selected species include elephants, bonobo apes and humans.

On the other hand, r-selected species are the opposite. They are very opportunistic. The attributes of a r-selected species include a short maturation tim, breeding at a young age, a short lifespan, producing many offspring quickly, small offspring, high mortality rates of young, and nonexistent parental care. Examples of r-selected species include waterfleas, insects, and bacteria.

http://www.bioinquiry.vt.edu/bioinquiry/cheetah/cheetahpaid/cheetahhtmls/poprK.html

I'm not an expert in this area, but I've some exposure to the issues involved because of it is an area of policy I've delved into. Anyone with a background in marine biology could add a lot, I'm sure.