Measures introduced over a decade ago to protect spawning cod in the Firth of Clyde were “too little, too late” according to a new study published in the ICES Journal of Marine Science which shows 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 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 nephrops and scallops, in the greater part of the area.
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.
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.
Previous studies using genetics, tagging and microchemistry found that cod inhabiting the Clyde are reproductively isolated from other resident groups of the West of Scotland. The researchers compared data on the number of adult fish regularly found in the area and compared it to data on the two other sub-populations of cod off the west coast of Scotland.
Ms Clarke added: “Mortality may have remained high because young cod are still caught as a by-catch 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.”
The measure appears to have been too little, too late and whilst we cannot change the past, we must recognise the failures of the politicians and fisheries managers and implement solutions for the future which manage populations within an ecosystem context.
Additional material regarding the fishery induced changes to maturation of cod, haddock and whiting may be found here.
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