Fishing closures are ineffective if the stock has already collapsed and is subject to by-catch
The University of Glasgow News reports 13th August 2015: Measures introduced over a decade ago to protect spawning cod in the Firth of Clyde were “too little, too late”, a new study finds.
Data published in the ICES Journal of Marine Science, showed no evidence that a seasonal closure of part of the Firth had led to local recovery of cod numbers or a reduction in overall mortality.
The researchers from the University of Glasgow and Marine Scotland Science say implementing spawning closures on nearly collapsed stocks may be why such measures often appear to have been ineffective.
The annual closure of the spawning ground was introduced in March 2001 to allow cod to reproduce without being caught by trawlers, while still allowing the targeting of scampi and scallops, in the greater part of the area.
Before the closure there was a clear seasonal peak in fishing effort corresponding to the spawning time of cod in this area with high catch rates. Placing the Clyde off limits was also intended to avoid an increase in fishing activity as a consequence of a spawning closure introduced in the Irish Sea in 2000. Joanne Clarke, a PhD student who led the study under the supervision of Dr Peter Wright of Marine Scotland Science and Dr David Bailey at the University of Glasgow, said: “Fish that congregate at predicable locations and times to spawn are often vulnerable to over-exploitation. Seasonal closures of fishing grounds have been implemented around the world in an attempt to alleviate such impacts, but the effectiveness of these measures is rarely tested.”
Ms Clarke added: “Mortality may have remained high because young cod are still caught as a bycatchBycatch The part of a fishery catch that is not a legal target of the fishery. Bycatch may be retained and landed but is usually discarded (released or returned to the sea, dead or alive). Examples: sea turtles caught in a longline fishery, sharks caught while fishing for swordfish, small or undersize red snapper caught when fishing for larger red snapper, and target species caught after a quota or limit has been reached. in the scampi fishery in the area, and the predation rate may have increased due to an expanding whiting population.
“The spawning closure is justified on the basis that it has reduced targeted fishing effort on spawning cod, and prevents displaced fishing effort from the Irish Sea. So in that respect, while we don’t know the full reasons preventing cod recovery, the least we could do is allow the remaining fish to spawn undisturbed.
“We cannot change the past, but we can address the future by managing populations within an ecosystem context. Spawning closures are not enough to manage populations when numbers are too low to withstand environmental fluctuations and additional sources of mortality. The measure appears to have been too little, too late.”
Source: University of Glasgow News, 13th August 2015. For full details, see
http://www.gla.ac.uk/news/headline_416059_en.html
Marinet observes: Is it not obvious that if you allow a stock to collapse (its spawning stock is reduced to a level where it can no longer effectively reproduce) then recovery in that stock is likely to be perilous and uncertain? And, if you allow the area to still be fished for other species (in this case, prawns) then is it not obvious the fish stock that is meant to be protected by no fishing will still actually be subject to fishing as a by-catch, thus negating the “no-fishing” protection?
At which school of fisheries management are these fishery managers learning their profession?
