Humans the biggest threat to marine species
October 12, 1998
By Environmental News Network staff
(ENN) -- Seaweb, an organization devoted to raising public awareness of the world ocean, has issued its monthly Ocean Update for October, and the news is not good. The update summarizes research on fisheries, global warming and bycatch. In all of these categories human impact on marine species is the biggest threat they face. Some of the studies reviewed:
The barndoor skate, one of the largest skates in the northwest Atlantic, is close to extinction as a result of being killed as by-catch in cod, redfish and other trawl fisheries. The report's authors estimate that in a large fisheries area south of Newfoundland, the barndoor skate population probably numbered some 600,000 individuals in the 1950s; by the 1970s, this number was likely around 500. The authors also say that if a large, easily identified species can dwindle away in a well-surveyed area, then the fate of poorly-known species is probably worse.
Black guillemots have only been hanging around in northern Alaska for the past 25 years, but it looks like they're moving on as a result of global climate change. Arctic sea ice, on which guillemots rely as refuge and as habitat for the Arctic cod on which they feed, is retreating, forcing the birds to fly farther in search of food. The guillemots' decline is, according to the author of the study, one of the "first documented biological effects" of climate change in the Arctic.
Spectacled eider population declines on the Yukon-Kuskokwim Delta, Alaska, are probably the result of eating lead shot. The populations have declined rapidly during the 1980s and low adult female survival is the likely cause of the decline. The authors found that adult females exposed to lead prior to hatching their eggs survived at a much lower rate each year than females not exposed to lead before hatching.
Gentoo and Rockhopper penguin populations on the Falkland Islands have undergone precipitous declines. The gentoo penguin population has fallen about 43 per cent and the Rockhopper penguin population has declined about 90 percent since surveys were first conducted in 1932/33. Recent monitoring suggests that the declines in both species are continuing. The news is particularly bad for the rockhopper since the Falklands represent the world's most important breeding site for the species.
King penguins, another Falklands penguin, is the only species that seems to be thriving; their numbers have increased by 700 percent -- to about 400 pairs -- since 1980-81, in line with worldwide trends for this species. The fourth main Falklands penguin, the Magelannic, was not included in the census because of the difficulties associated with counting a species that nests in burrows.
Humpback whales, predominantly calves, are suffering from more fishing line entanglements and human-related deaths off the coasts of Hawaii than ever before. Figures showed an increasing trend of entanglement in natural fiber and synthetic lines since 1992 and a three-fold increase in death and entanglement occurrences related to human activity in 1996.
The Australian king prawn fishery was studied to assess levels of bycatch, and the news could hardly be worse. Researchers chose an oceanic prawn trawl fishery off the coast of southeastern Australia that involved some 280 vessels. They monitored four of the largest and most important fleets (out of 11). In catching an estimated 1,579 tons of prawn, the four fleets also caught some 16,435 tons of bycatch involving 80 species of finfish, crustaceans and mollusks. This makes the bycatch to prawn ratio 10.4:1. Of this, an estimated 2,952 tons was retained for sale and the remainder, 13,458 tons, was thrown overboard.
Florida Keys coral reef fish stocks have been something of a mystery to scientists because of a lack of data. However, a recent study showed that of the 35 fish stocks looked at, which included 16 grouper species, 13 of snapper, five of grunt, and the great barracuda, 22 -- or 63 percent -- were in an "overfished" condition. The authors of the study said that given the inevitable increases in fishing effort and habitat degradation by rapid human population growth, overfishing is likely to continue. They also felt that the dynamics and structure of the overall coral community may have already seen "substantial changes."
Sharks are severely threatened, and a failure to enact state regulations by Atlantic and Gulf Coast states is seriously undermining federal efforts to protect them, according to a report released by the Ocean Wildlife Campaign. Five years ago, the National Marine Fisheries Service instituted a fishery management plan to prevent overfishing of sharks in federal waters but the sharks aren't seeing the lines, apparently, and move in and out of federal waters and get caught in state waters where they aren't protected. In addition, says the report, sharks are threatened by high levels of bycatch and by destruction of bays and estuaries that are important nursery grounds for their young.
Seaweb is a multimedia public education project designed to raise awareness of the world ocean and the life within it. For a complete reading of Ocean Update, visit Seaweb's Internet site, www.seaweb.org. For more information, contact email@example.com.
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