Page 12. MAINE COASTAL NEWS April 2016 Commercial Fishing News
NOAA releases draft national strategy to reduce bycatch in marine fi sheries NOAA is inviting public comment on
M C F N
its draft National Bycatch Reduction Strat- egy. The proposal continues the nation’s momentum on reducing bycatch—when fi shermen catch fi sh they don’t want, can’t keep, or aren’t allowed to keep. Bycatch can also occur when fi shing gear harms or kills marine mammals, seabirds, corals, sponges, sea turtles, or protected fi sh. ”Bycatch is a complex, global issue that
can threaten the continued sustainability and resiliency of our fi shing communities, economies and ocean ecosystems,” said Ei- leen Sobeck, assistant NOAA administrator for fi sheries. “The United States is doing its part to reduce and prevent it. This strategy outlines how NOAA is working on multiple fronts with many partners to develop inno- vative solutions to minimize bycatch here and helping others do so abroad.” The draft strategy provides a coordi-
nated national approach for NOAA and its partners to identify and address how bycatch issues diff er by region. It also addresses domestic and international program areas such as bycatch monitoring, research, man- agement, program evaluation, enforcement and communication. “This strategy recognizes both where
we’ve been and where we are going and po- sitions the United States to build on decades of bycatch reduction work under the author- ity of the Magnuson-Stevens Act, the Ma- rine Mammal Protection Act, Endangered Species Act, and other relevant laws,” said Sobeck. “Our goal is to reduce bycatch and encourage use of unwanted catch, keeping our fi sheries sustainable while conserving and recovering protected species.” The strategy completes a series of
bycatch-related documents out this month. A report to Congress, released last week, shows the agency’s progress in improving technologies and changing fi shing practic- es to reduce and prevent bycatch. Earlier this week, NOAA Fisheries distributed an update to its bycatch statistics showing how bycatch varies by fi shery and type of gear. “Bycatch is an issue NOAA Fisher-
ies cannot address alone,” said Richard Merrick, Ph.D., chief scientist for NOAA Fisheries. “Our strategy involves close collaboration with fi shermen, management partners, researchers, and other stakeholders to fi nd win-win solutions.” NOAA Fisheries is accepting public
comment at this link on the draft strategy through June 3. When the strategy is fi nal, NOAA will consult with its partners and stakeholders to prepare regional action plans.
Potential Western Atlantic Spawning Area Found for Atlantic Bluefi n Tuna Scientists from NOAA’s National Ma-
rine Fisheries Service (NOAA Fisheries) and the University of Massachusetts Boston have found evidence of Atlantic bluefi n tuna spawning activity off the northeastern Unit- ed States in an area of open ocean south of New England and east of the Mid-Atlantic states called the Slope Sea. The fi ndings, published March 7 in the
Proceedings of the National Academy of Sci- ences, suggest that the current life-history model for western Atlantic bluefi n, which assumes spawning occurs only in the Gulf of Mexico, overestimates age-at-maturity. For that reason, the authors conclude that west- ern Atlantic bluefi n may be less vulnerable to fi shing and other stressors than previously thought.
Prior to this research, the only known
spawning grounds for Atlantic bluefi n tuna were in the Gulf of Mexico and the Mediter- ranean Sea. The evidence for a new western Atlantic spawning ground came from a pair of Northeast Fisheries Science Center (NEFSC) research cruises in the Slope Sea during the summer of 2013. “We collected 67 larval bluefi n tuna
during these two cruises, and the catch rates were comparable to the number col- lected during the annual bluefi n tuna larval survey in the Gulf of Mexico,” said David Richardson of NOAA’s Northeast Fisheries Science Center (NEFSC), lead author of this study. “Most of these larvae were small, less than 5 millimeters, and were estimated to be less than one week old. Drifting buoy data confi rmed that these small larvae could not possibly have been transported into this area from the Gulf of Mexico spawning ground.” Larvae collected during the cruises
were identifi ed as bluefi n tuna through vi- sual examination and genetic sequencing. To confi rm the identifi cation, larvae were sent to the Alaska Fisheries Science Center laboratory in Juneau, where DNA sequences verifi ed that the larvae were Atlantic bluefi n tuna.
A single bluefi n tuna can spawn mil-
lions of eggs, each of which is just over a millimeter in diameter, or the size of a poppy seed. Within a couple of days these eggs hatch into larvae that are poorly developed and bear little resemblance to the adults. Larval bluefi n tuna can be collected in plank- ton nets and identifi ed based on their shape, pigment patterns and body structures. Atlantic bluefi n tuna (Thunnus thyn-
nus) is a high value species with a unique physiology that allows it to range from the tropics to the sub-arctic, in coastal to international waters. As a highly migratory species, Atlantic bluefi n tuna is assessed by the Standing Committee on Research and Statistics (SCRS) of the International Commission for the Conservation of Atlan- tic Tunas (ICCAT) as distinct eastern and western stocks separated by the 45 degree west meridian (or 45 w longitude). The U.S. fi shery harvest from the western Atlantic stock is managed through NOAA Fisheries’ Atlantic Highly Migratory Species Fishery Management Plan. For many years, global overfi shing
on this species was prevalent, resulting in substantial population declines. However, recent international cooperation in manag- ing catches has contributed to increasing trends in the abundance of both the eastern and western management stocks. The west- ern stock, targeted by U.S. fi shermen, is harvested at levels within the range of the SCRS’ scientifi c advice. This research may help to resolve a
longstanding debate in Atlantic bluefin tuna science. It had long been assumed that
bluefi n tuna start spawning at age 4 in the Mediterranean Sea and age 9 in the Gulf of Mexico. Electronic tagging studies begun in the late 1990s revealed that many bluefi n tuna, assumed to be of mature size, did not visit either spawning ground during the spawning season as expected. This led some to propose that these larger fi sh were not spawning, and instead the age-at-maturity for western Atlantic bluefi n tuna was 12-16 years, rather than 9 years, as was assumed in the stock assessment. Molly Lutcavage at the Large Pelag-
ics Research Center of the University of Massachusetts Boston, a co-author on the study, was a consistent supporter of an alternate hypothesis—fi sh that did not visit the Gulf of Mexico and Mediterranean Sea were spawning elsewhere. The research team used electronic tagging data from the Lutcavage lab to present an alternate model of western Atlantic bluefi n tuna spawning migrations. Only the largest bluefi n tuna, those over
about 500 pounds, migrate to the Gulf of Mexico spawning area. After these fi sh exit the Gulf of Mexico, they swim through the Slope Sea rapidly, on their way to northern feeding grounds. On the other hand, smaller fi sh, ranging in size from 80 to 500 pounds, generally spend more than 20 days in the Slope Sea during the spawning season, a duration consistent with spawning. “Last year, we demonstrated using
endocrine measurements that bluefi n tuna in the western Atlantic mature at around 5 years of age. That study, and ones before it, predicted that these smaller fi sh would spawn in a more northerly area closer to the summertime foraging grounds in the Gulf of Maine and Canadian waters,” Lutcavage said. “The evidence of spawning in the Slope Sea, and the analysis of the tagging data, suggests that western Atlantic bluefi n tuna are partitioning spawning areas by size, and that a younger age at maturity should be used in the stock assessment.” Researchers also found that individual
tuna occupy both the Slope Sea and Medi- terranean Sea in separate years, contrary to the prevailing view that individuals exhibit complete fi delity to a spawning site. Re- productive mixing between the eastern and western stocks may occur in the Slope Sea and the authors contended that population structure of bluefi n tuna may be more com- plex than is currently thought. “Past analyses of Atlantic bluefi n tuna
population structure and mixing between the western and eastern Atlantic stocks may need to be revisited because they do not account for the full spatial extent of west- ern Atlantic spawning,” Richardson said. “So much of the science and sampling for Atlantic bluefi n tuna has been built around the assumption that the Gulf of Mexico and Mediterranean Sea are the only spawning
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