Major international research project challenges current management thinking.
Fishing News 27. March 2012
AS THE EU steps up its efforts to make fishing gear more selective in its bid to ban all discarding, a major new international scientific report argues that selective fishing is damaging to fish stocks and eco systems, reports Tim Oliver.
The report*, in the journal Science, supports a view held by some fisheries scientists that if fishing effort is cut too much and directed too narrowly at target species and sizes, stocks become too big for the available food supply and fish do not grow. One of the leading advocates of this point of view is Icelandic fisheries scientist Jon Kristjánsson, who is well known in the UK and Ireland and whose views have sparked debate over fisheries management for some years.
The researchers argue that balanced harvesting with a moderate level of fishing mortality reduces the adverse ecological effects of fishing and supports sustainable fisheries more effectively than current management strategies.
Fishing across the widest possible range of species, stocks, and sizes in an ecosystem in proportion to their natural productivity maintains their relative size and species composition. The report says that increasing fishing selectivity to catch a small group of species and sizes does not maximise production or minimise the ecological effects of fishing, as conventional fisheries management claims. The research includes results from modelling of 30 ecosystems worldwide and was carried out by both fisheries and conservation scientists from leading marine and fisheries research institutions from around the world.
Dr Tony Smith, one of the report's authors, says: "Traditionally, fisheries have used species and size limits, gear technology and spatial and temporal fishing restrictions to increase selectivity. This means they capture species, sexes, and sizes in proportions that differ from their occurrence in the ecosystem.
"This has been intended to help sustain target populations, protect rare and charismatic species, and minimise the capture of unwanted species and sizes (by-catch). "But selective removals, except at economically unacceptably low levels of harvest, inevitably alter the composition of a population or community and, consequently, ecosystem structure and biodiversity."
Professor Richard Law of the Department of Biology at the University of York, analysing the report suggests that the approach of increasing selectivity in the size and species of fish that can be harvested should be reconsidered. He says that in theory, increased selectivity helps prevents 'growth overfishing' - the loss of future yields if juveniles are caught before they are allowed to reproduce - and reduces by-catch of non-targeted species. But data from 30 fisheries worldwide shows that these benefits occur only where fishing mortality is so low that the fishery is not economically sustainable. The researchers found "compelling evidence" that when fishing is spread over more stocks and sizes, yields are higher and harmful impacts such as biomass depletions are lower.
"There are potentially real benefits to be gained by moving towards more balanced exploitation of marine ecosystems," he says. Professor Law adds that working with other scientists he has checked the sums underlying the argument and has just published an article in the ICES Journal of Marine Science.
"These simulations also show there are potentially real benefits to be gained by moving towards more balanced exploitation of marine ecosystems," he says.
* Science 2 March 2012: Vol. 335 no. 6072 pp. 1045-1047 'Reconsidering the Consequences of Selective Fisheries'.
Icelandic fisheries scientist Jón Kristjánsson, who has argued against selective fishing for many years, has just been included in Seafood Executive's 'The Power 100' - World top 100 in the seafood industry. Seafood Executive is a quarterly supplement to Seafood International magazine published by Intrafish news media. He is one of the few scientists who until now have challenged the accepted maxims of fisheries management in Iceland and elsewhere and his opinions have sparked plenty of debate.
- says Icelandic fisheries scientist Jón Kristjánsson - Fishing News 4. May 2012
EXPERIENCE with management of cod stocks in Iceland since 1976 supports the findings of research reported in the article in the journal Science.
In this exclusive statement to Fishing News. Icelandic fisheries scientist Jón Kristjánsson says this should be a wake up call to EU fisheries managers and ICES scientists to abandon failed orthodox fisheries management in favour of more relaxed regimes.
The paper in Science is the strongest weapon that the industry has ever had. But how will the ICES scientists react to this challenge to orthodox science? Perhaps do nothing and hope this will fade away. Now is the time for the fishing industry and media to press scientists and ask questions. For the last quarter century they have strangled the industry with wrong premises, according to the Science paper. They have been warned and criticised by fishermen and independent scientists for a long time, but ignored the warnings, even though results of orthodox management are dreadful.
A large scale experiment was conducted in Iceland when the foreign fleet left Icelandic fishing grounds in 1976. A radical change in fishing patterns took place, and the mesh size in the codend of trawls was increased from 120 to 155mm to protect small cod and allow them to grow for a little longer.
The immediate effect was that one year class was added to the stock - the age at capture moved from 3-year old to 4-year old fish. At the same time growth (weight at age) slowed, indicating shortage of food. The weight of 6-year old cod went down from 4 to 3kg. Landings went down by 30% and a catch quota system was introduced in 1984. At the start of this management experiment the average catch of cod at Icelandic grounds had been 450.000 tons per year for a long time. But since then cod landings deteriorated lo 150,0001 per year and have remained at this level for many years.
At present the cod quota is 170,000t - half of what they were before the disastrous introduction of present management measures. No lessons have been learned -instead of returning to the former fishing pattern, management screws were tightened even more, fishing pressure reduced further, and protection of small fish increased by area closures.
Similar reductions in cod have been reported in the N. Sea. Irish Sea and West of Scotland after increases in mesh sizes, quotas cuts and reduction of fishing pressure. The only exception is the Barents Sea, where politicians have for many years allotted larger quotas than ICES advised. The stock continually increased. Even minimum landing sizes were decreased to allow for the Russian catches of small cod.
Example from Africa
An interesting case study comes from Lake Kariba in Africa, where the two countries on either side of the lake, Zambia and Zimbabwe, have had different management regimes. The two sides of the lake are separated by a deep gulley in the centre of the lake and the artisanal fisheries on both sides focus on the near shore, shallower areas, each with their specific fish communities. This situation allows a large scale empirical experiment in which the two separate fisheries can be compared.
The Zimbabwean side has had strict controls with licensed fishing effort, regulated gears and mesh sizes (only gillnets allowed, with a minimum 100mm mesh size). But on the Zambian side there has been open access with ensuing high fishing pressure and changing patterns for increased use of small meshes and customary use of traditional, but illegal, methods such as drive (beat) fishing. The results after 40 years (J. Kolding pers.com) show Zambian catches are six times higher than the Zimbabwean side, with no symptoms of overfishing.
According to the results presented in the Science article the EU management regime of selective fishing with catch and species quotas should be abandoned. In practical terms this means it should be replaced with almost free access for vessels with fishing permit, and no restriction on days at sea and no species specific catch limits.