Deep sea fish may be in worse trouble than we thought. A study published this week shows that the impact of fishing extends far deeper than previously shown.

Using a huge collection of data from scientific trawls dating back to 1977, David Bailey, of the University of Glasgow, and colleagues found fish abundance fell significantly at depths from 800 to 2,500 metres. The maximum depth for commercial fishing is around 1,600 metres.

Bailey originally reported his findings at the 2008 Ocean Sciences Meeting in Orlando, Florida (see: Fishing trawlers have double the reach). Now the research has been published in Proceedings of the Royal Society B.

“What we think is happening is fish are getting impacted if they live any part of their life within the fishing grounds,” Bailey told Nature News earlier this week. “As a result they’re not living to spread out into their normal range.”

Declines of some species are spectacular. Roundnose grenadier (Coryphaenoides rupestris), which are targeted by fishing boats, declined in abundance by 41% between 1977 and 2002. Polyacanthonotus rissoanus, which are not targeted, dropped 77%.

Jennifer Devine, a fisheries scientist with the middle depth fisheries and acoustics group at New Zealand’s National Institute of Water & Atmospheric Research, told Nature:

That the impact of fishing is seen deeper than fisheries operate, as suggested by this paper, is not surprising. Many studies, mostly terrestrial, have shown that trouble at the edge of a species range presages trouble over the entire range.

The work by Bailey et al. (2009) is exciting because they have data that cover most of the depth distribution of several deep-sea species from a moderately long time period; this is rare. Most data collected on deep-sea fishes either encompasses only part of their distributional depth range or are from relatively short time periods. This paper provides more evidence that deep-sea fisheries may have wide-reaching effects and are difficult to manage sustainably.

See also

Deep water fish decline concerns – BBC

Devine’s 2006 Nature paper, Deep-sea fishes qualify as endangered.

More news from this week’s Royal Society journals

A spectacular new “dracula” fish has been discovered, the only species of carp-like fishes to have “teeth”. – Daily Telegraph

Rhesus macaque mothers are about twice as likely to let a howling infant have its way during very public tantrums than during more private moments, says Stuart Semple of Roehampton University in London. – Science News