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  Photo credit: John Hyde Fish TrackingAbstract: "Do we still have a body?" "Yep, but I've extracted the ear stones . . . and the DNA says it's a black gill." This is not an unusual exchange in the genetics and physiology laboratory of Russell Vetter at the National Marine Fisheries Service (NMFS). The NMFS in La Jolla attempts to balance goals of conserving the ecosystem with maintaining viable fisheries off the Southern California coast. Otoliths (ear stones) and DNA sequences are two sources of data for achieving these goals. To maintain viable fisheries for future generations, we need to make accurate predictions in fish numbers now and in the future. Fishery scientists often focus on early life stages of fishes (eggs and larvae) because they are easier and cheaper to sample than adults. Sampling these early stages helps us to identify factors contributing to fluctuations in the fishery. For example, cold years following El Nino warm periods correspond to high numbers of offspring for some rockfish species. If we can predict effects of environmental changes on fish stocks, we can make reasonable management decisions to secure fisheries now and in the future. My work focuses on rockfishes. Rockfishes are often marketed as "rock cod" or "Pacific red snapper" in the grocery store. These commercially fished species are also popular targets of sportfishing boats. They can be found at offshore seamounts or in local kelp beds. Over 50 species of rockfish occur off Southern California, some with distributions extending as far north as Alaska. Each species of rockfish has its own depth preference. Some species can be found as shallow as 20 feet, whereas others are found at over 1,000 feet in depth. As adults, many near-shore (shallow-dwelling) rockfishes stay put on one reef or rocky outcrop. Rather than lay eggs like most marine fish, female rockfishes give birth. They can release hundreds of thousands of larvae in one brood. These tiny larvae are at the mercy of the currents, and some remain offshore for up to four months. By staying offshore, they may avoid coastal predators. They feed on small, free-swimming and floating zooplankton while they grow. During their early life, rockfishes become stronger swimmers, but little is known about this time in their life. One goal of my research is to better understand factors contributing to the survival of these young fishes that somehow find their way back to the coastal areas where they spend adulthood. To study the early life period in fishes, we obtain larval fish from net tows in a research program called CalCOFI (the California Cooperative Oceanic Fisheries Investigations). CalCOFI is supported by a joint effort among the California Department of Fish and Game, the National Marine Fisheries Service and Scripps. Before current DNA sequencing technology, few rockfish larvae were identifiable to species, so there were few scientific data to support management decisions for them. The CalCOFI program collects scientific data by conducting ocean surveys (including net tows) four times per year in a set sampling grid in the ocean. These data have been collected for over 50 years off Southern California. Since these data are collected at the same locations year to year on a grid pattern, they are considered less biased than the data on the adults caught by fishermen who always go where they know the fish are biting. Two of many goals in CalCOFI are to construct trends in spawned numbers of fish larvae and to estimate adult spawners (adult fish stock) from year to year. The data that fishery biologists often obtain from larval fish might seem surprising. We use the ear stones, or otoliths, to estimate fish age (in days). As fish larvae grow, the daily rings in their otoliths can be counted much like annual rings in a tree trunk are used to age an oak. By aging them and knowing where they were sampled, we can use our knowledge of ocean currents to identify areas where these larvae were born. We also collect genetic (DNA) data for larvae using forensic methods. Larvae of some species, like sardine and anchovy, can easily be identified visually because they have a distinct shape or fin pattern. With most species of rockfish larvae, however, DNA data are needed to make the identifications. At NMFS, we have been able to use adult samples from diving and fishing to develop a database of known rockfish DNA sequence data. We use these data to identify unknown larvae. Advances in biotechnology have allowed genetic methods to be accessible to fisheries biologists. Biologists are embracing all tools that help them balance priorities of protecting the livelihood of fishermen and conserving our patch of ocean habitat off Southern California. The text of the above article originally appeared in the San Diego Union-Tribune on Jan 23, 2002. Copyright SAN DIEGO UNION TRIBUNE PUBLISHING COMPANY Jan 23, 2002. Useful websites: Southwest Fisheries Science Center http://swfsc.ucsd.edu Daniel Poland National Ocean Service Marine Sanctuaries Page http://www.sanctuaries.nos.noaa.gov/oms/oms.html UCSD Underwater Club (Seadeucers) Website http://www.seadeucers.com/ Milton Love's (UCSB) Website and Home of the American Sebastes Society http://www.id.ucsb.edu/lovelab/index.html Ray Troll's Website and Online Store http://www.trollart.com/ |
Scientific Sleuthing
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