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Green Grazing: Ocean Theme
Biodiversity by Ian Parnell, August 29, 2007
Seabirds in trouble: I came across a couple of posts on blogfish about large reductions in a population of over wintering sea birds in the Pacific Northwest and starving seabirds showing up along the coast of Florida. Sounds similar to a blurb I posted a couple of weeks ago about breeding problems for seabirds off the coast of Scotland. For the Scottish birds, climate change was named as the suspect, charged with raising ocean temperatures, which changed the plankton regimes the birds' food sources depended on, which in turn reduced the food supply the birds depended on to feed their young. Similar charges are still under consideration for the seabirds in the Pacific Northwest and Florida, but more investigation is required. It’s clear we’ve got a lot to learn about the ocean ecosystem.
Sustainable Fisheries
Low tuna catches: An article in Planet Ark reports that the Indian Ocean Tuna Commission (IOTC) says the tuna catch over the first four months of 2007 (a mere 75,000 tonnes) is the lowest since the same period in 1996. But is it climate change or overfishing? This fishery probably has more co-ordinated monitoring and research associated with it than all the seabird programs in the world (someone please tell me I’m wrong), yet fisheries scientists with the Indian Ocean Tuna Commission say they probably won’t be able to know has caused these low catches for a couple of years. The Planet Ark story quotes a fish plant manager as saying tuna catches are ‘recovering’ since prices increased in April. It’s hard to rule out any cause with just landed catch data, though – changes in landed catch could be due to climate change causing a change in depth distribution of tuna, or lower populations from heavy fishing over the last few years, or maybe just lower fishing effort due to lower tuna prices. The scientists will need to have data on catch per unit effort, sea surface temperature, population size and age structure, an estimate of the size of the illegal catch and catch by nations not part of IOTC and probably the landed value of catch to assess the various potential causes. That’s a lot of work. More...
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