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CALIFORNIA WILD

LETTERS TO THE EDITOR

Fishing’s Net Loss

Some fish are rich in essential oils such as the highly-touted omega-3s. But if tuna and swordfish are on your plate, they are rich in another kind of oil—cheap petroleum. One of the world’s biggest beneficiaries of cheap oil is the longline fishing industry pillaging our fragile ocean ecosystem. This problem is rooted in the overfishing of the oceans outlined in your interview with Jeremy Jackson, “The Rise of Slime” (Winter 2004).

A groundbreaking new study soon to be published in The Encyclopedia of Energy explores the energy efficiency of a number of world fisheries, including longlining. Taking into account the material and petroleum required to power a wide variety of industrial fishing vessels, Peter Tyedmers of Canada’s Dalhousie University compares the amount of edible protein in their catches.

The results are shocking. According to Tyedmers, amongst fisheries targeting high value species, “it is now common for direct fossil fuel energy inputs alone to exceed nutritional energy embodied in the catch by at least an order of magnitude.” In an earlier preliminary study of 54 North Atlantic fisheries from five countries, Tyedmers uncovered a wasteful paradox: “the availability of abundant energy...enables most contemporary fisheries to continue even when stocks are in decline.”

Vessels targeting shrimp, tuna and swordfish are at the top of the list of the fisheries with the most inefficient “edible protein return on investment.” By comparison, the most efficient fish species to target are small deep sea species such as menhaden and mackerel, most of which are ground up into fishmeal or used for oil.

The tuna and swordfish fisheries are especially petroleum-hungry, consuming three times the average energy of most fishing vessels in his study. Between 1986 and 1999, the amount of energy consumed by these fisheries skyrocketed fourfold.

Tyedmers’ study identifies a new problem associated with targeting large predatory species such as tuna and swordfish, adding to an already lengthy and damning list. These fish are caught by longlines which can stretch up to 50 miles and carry hundreds of baited hooks. Longlining creates a non-selective killing field that annually snags and drowns upwards of 4 million endangered whales, dolphins, sea turtles, porpoises, sharks, seabirds, sea lions, and billfish such as marlins in the Pacific alone.

The Pacific leatherback turtle has been the species hardest hit by longlining. The leatherback’s female nesting population has collapsed by 95 percent in the past 22 years. This sea turtle is expected to go extinct within the next few decades unless there is action to reduce the mortality of adult turtles.

Fish may be highly valued for their essential oils, but this is the kind of oil we would be better off doing without.

Robert Ovetz
Sea Turtle Restoration Project
Sausalito, CA

View From Down Here

One has to look no further than Ann Richardson’s own letter defending SUVs (Winter 2004) to see what is wrong with many SUV drivers. She defends her use of an SUV because it rides high off the road: “a low or small car does not have the visual capability that a taller vehicle does. It is important when driving down the highway during rush hour to have good visibility.” Few people would disagree. Ms. Richardson says, however, that it is only important for her to be able to see ahead—that the other drivers in shorter cars do not need to see ahead while driving. She fails to understand that if we all drove shorter cars, we could all see ahead equally, but that it is precisely the selfishness of the SUV drivers which blocks our views. I guess Ms. Richardson is just more important than the rest of us.

Gregory R. Wilson
San Francisco, CA

Cave Development

I very much enjoyed Dr. Jerold Lowenstein’s article on “Evo-Devo: The Shape of Things to Come” (Fall 2003).

It seems to me that it might be worthwhile to investigate the structure and effects of Hox genes in cave-dwelling organisms. There are many arthropods and some fish that are identical to non-cave-dwelling relatives except that the cave-dwellers have lost light-related characteristics such as sight, eyes, and/or coloration. Research involving these species might be especially productive in examining the mechanisms by which Hox genes are altered and by which they induce their effects because:

1) The age of many such caves can be determined, thereby setting an upper limit on the length of time it took for such mutations/trait variations to have occurred and become prevalent.

2) It may be possible to identify the specific genes that produce these trait variations.

3) Many of these caves are young on a geologic/evolutionary time scale, so that the loss of sight, eyes, and/or coloration by the cave-dwelling species must have occurred over a relatively short period of time. This supports the idea that cave-dwellers and their relatives are genetically very similar, and might enable investigation of the rate at which such genetic-variations occur.

4) These types of trait variations are evolutionarily convergent, in that they occur independently in many different caves. Perhaps it can be determined if the mechanism is consistent between different organisms in different caves.

To me, the biochemical mechanisms that produce adaptations to specific conditions are the most mysterious aspect of evolution. Examination of the mechanisms that have repeatedly and separately produced similar adaptations in widely dispersed cave-dwellers could shed more light on this topic.

The author responds: The questions about the loss of sight in cave-dwelling organisms are very interesting. I haven’t come across any research in this area, but I agree that this is very likely one of those situations where the hox genes kick in. Mutations in genes like ‘eyeless,’ which would handicap most species, would have little or no effect on cave-dwellers and so might be tolerated. This would make a good research project for someone. Incidentally, cave-dwellers don’t only lose their eyes and their pigmentation, they also develop extraordinarily long appendages.