Vol. 2, No. 2 Contents
Headline Back Issues Spring 1998
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Fishery research (con'd) All of this material is entered into one of several extensive databases that NMFS scientists use to determine the abundance and survival rate of fish that are mature enough to be harvested; the geographic distribution of species; how plentiful their food supply is and whether it is changing; their spawning patterns; ecosystem changes that may affect them; and whether their populations are increasing, decreasing, or holding steady. The link between research and management
One of the most troublesome findings scientists may encounter in their research is that a stock has been over-fished. NMFS' September 1997 report to Congress on the status of US fisheries listed 86 species as over-fished and 10 species as approaching over-fished status based on the criteria specified in the Magnuson-Stevens Fishery Conservation and Management Act of 1976. The Act, reauthorized in October 1996, mandates that NMFS rebuild over-fished stocks and protect and enhance essential fish habitat. Regional councils manage US fisheries in accordance with the Magnuson-Stevens Act. Of the 26 stocks under the New England Fisheries Management Council's (NEFMC) geographical area of authority, 12 are classified as over-fished, and two others are approaching over-fished status. In 1984, New England fishermen landed about 96 million pounds of cod (43,439 metric tons). By 1996, landings decreased to about 31 million pounds (14,197 metric tons) due to declining stocks. This prompted scientists to recommend a 63 percent reduction in cod takes, which NEFMC has implemented for this year's Gulf of Maine cod catch. For most species, the definition of over-fishing is based on the number of mature fish killed by fishing (mortality rate), but according to Steve Murawski, chief of NEFSC's Population Dynamics Branch, considering stock level along with mortality rate gives a more accurate picture of a stock's status. For example, on Georges Bank, even though closures have lowered mortality rates, the stock level remains low as a result of past over-fishing. In this case, basing management decisions only on improving mortality rates would overlook the fact that the stocks are still depleted. Murawski noted that NMFS is in the process of revising guidelines for defining over-fishing. Elbow-deep in data On leg four of the spring groundfish survey, at stations selected to provide a representative sampling of the Gulf's depth zones and geography, scientists collected information on food habits, population distribution, and stages of maturity. The trawl net used on research surveys has a finer mesh than a commercial fishing net, allowing smaller, younger fish to be caught, providing information about the number of fish likely to enter the fishery as they mature but NEFSC scientists emphasize that their survey procedures have been developed to minimize the catch taken on research cruises while still allowing them to get a representative sampling of species. At each station, following a 30-minute trawl, the catch was sorted by species into plastic buckets and bushel baskets. The scientists and other participants on board worked in pairs, in which a "cutter" examined the fish, and a "recorder," wrote down the information on waterproof log sheets. While lobsters and crabs were measured and released, almost every other fish caught was measured, weighed, and tallied, and a representative sampling of each species was examined further for information on gender, reproductive maturity, and, in some cases, stomach contents. From many of the fish, scientists also removed otoliths, small bone-like structures in the fish's head that grow new layers as the fish ages, much as tree trunks grow new rings. Otoliths provide valuable information on a fish's age and growth history. In some cases, scales can also provide this information, as can other bones, and these may be collected instead. As watch chiefs, NEFSC biological technicians John Galbraith and Vic Nordahl reviewed their team's log sheets for accuracy, and Nancy McHugh, chief scientist for the cruise, reviewed them again. Paid prison inmates enter the logged information onto computer disks that are later transferred into NEFSC's database which, according to NEFSC fisheries biologist Linda Despres, also contains a system of checks to help catch errors that may have been made at sea or during data entry. Along with providing stock assessment information, survey cruises are an opportunity to collect special samples for other researchers' projects, and to bring back shrimp and herring for the fish and seals at Woods Hole Aquarium. Some live specimens starfish, anemones, and fish are also brought home to be exhibited at the aquarium. Assessment draws on other sources
Records of fish landed by commercial fishermen are also a valuable source of information in assessing fish stocks but do not provide all the information needed, said Frady. Several fishery management plans require that fishermen document landings of certain species, but there are inconsistencies in reporting, she noted. Also, fishermen's logs provide information on fishing "hot spots," which are not necessarily representative of the fishery as a whole. And commercial logs are more likely to include information on marketable species than for species that are less commercially valuable. In addition, fishermen are continually updating their equipment and methods, and increased landings could reflect greater fishing power rather than changes in the actual fish stocks themselves. Survey vessels, on the other hand, use the same methods they have for years, and the equipment has not changed much, so data collected on them can be compared directly from one year to the next, Frady explained. The Commonwealth of Massachusetts has argued against basing fishery management decisions on reported commercial landings. According to the Massachusetts Division of Marine Fisheries (DMF), because recent regulations have increased mandatory reporting requirements, records show more fish are being landed when that may not be the case only that more landings are being documented. But DMF says the perception that more fish are being landed is leading to quotas that are set too low. Massachusetts successfully sued the Secretary of Commerce and the Director of the National Marine Fisheries Service charging that a quota on scup was based on inaccurate and incomplete records of scup landings in the state. Frady said NMFS is considering an appeal. She said the quotas were based on available information. Should more figures come to light, NMFS can revise the scup management plan, she said. Though NMFS has had its share of critics, a recent independent review of its research methods by the National Research Council has validated the science behind NEFSC's stock assessments. "Scientists collect the same type of data each time," said Frady. "The more information you have, the better the assessment you can do." |
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"The assessments themselves result in advice to managers about what is happening with the stock. It's up to managers to decide what to do about it," said Teri Frady, NMFS Chief of Research Communications.
Fish stock assessment draws on other resources in addition to NEFSC's scientific surveys, including fishery surveys conducted by individual states and by Canada. According to Stratis Gavaris, fisheries scientist at the Canadian Department of Fisheries and Oceans (DFO), that country's methods of collecting and analyzing information and making recommendations to fisheries managers is very similar to that in the US. NMFS and DFO jointly evaluate the status of shared stocks, and before putting management policies into place, each agency brings its recommendations before the public.