The depletion of wild fish populations around the world due to overexploitation, habitat destruction, disease, environmental changes, and other factors has ignited an interest in fisheries stock enhancement. Several commercially important species in the U.S., such as the salmonid species of the Pacific Northwest, the striped mullet of Hawaiian waters, and the red drum of the Gulf of Mexico are being raised in hatcheries by the thousands and have been shown to augment wild fish stocks. Many other declining wild fish stocks are potential candidates for enhancement, but research indicates that not all populations automatically rebound upon the addition of hatchery-raised juveniles. One candidate on the west coast of Florida is the common snook, Centropomus undecimalis. The population around Sarasota, Florida has been suppressed in the past 30 years due to overfishing, increased housing and seawall developments along the creeks, and environmental extremes such as bouts of red tide and cold snaps. The closure of the commercial industry in 1957, sportfishing size restrictions, the promotion of recreational catch-and-release, and education through the Snook Foundation have helped, and stock enhancement is the next to join this suite of conservation tactics. Dr. Kenneth Leber and Senior Biologist Nathan Brennan of Mote Marine Laboratory in Sarasota are researching the efficacy of snook stock enhancement, and I was fortunate to work as an intern in Mote’s Center for Fisheries Enhancement for three months.

   In May 2002, over 2000 juvenile snook were released into the Sarasota creek systems. Bowlees Creek and Whitakers Bayou received a 50% increase in snook (original abundance was determined in an April pre-release study), while the control sites, North Creek and South Creek, received only a 10% increase. Hatchery fish were tagged using two cutting-edge methods: coded wire tags (CWT) and visible implant elastomers (VIE), both developed by Northwest Marine Technologies. Two months later, I was able to assist in the first round of sampling and tagging to determine post-release snook density estimates in the four creeks. The most favorable scenario would be a two-fold increase with an equal ratio of wild to hatchery fish in Bowlees Creek and Whitakers Bayou, but little change in the juvenile population structure of North and South Creeks (other than natural mortality trends). To analyze the population, we pulled seine nets at low tide at every 200 feet of each creek and sorted through the catch. I learned how to handle the target species, prepare and insert CWTs and VIEs, and record data on fish measurements and water quality at the site. The work was physically demanding and exciting as this study is the first of its kind to use such extensive tagging techniques in the field. The researchers question whether the creek systems can support more than 2 snook per 100 feet of suitable shoreline habitat. Data from the following sampling trips will help to sort through these questions.

   During our time back at the lab I entered the data from our sampling trips, compiled bibliographic information on pertinent stock enhancement articles, and cared for hatchery-raised snook and red snapper in the department’s tank systems. The fish maintained in the “wet lab” are currently identified by a number of tags in different tissues and are kept as part of an ongoing tag retention study. I was able to assist in a periodic check on the tags, which required anesthetizing the fish with a cocaine derivative. I was also fortunate to assist Mr. Brennan and Research Biologist John Ransier of the Port Manatee state hatchery in a red drum tag retention study. Over 2,000 one-month-olds were anesthetized and tagged with CWTs using Mark-4 machines fitted with “headmolds” for precise insertion into the tissue behind the eye. CWTs are typically not used in such small fish because it is time consuming and can result in high mortality. However, if tag retention remains high over the next year, the headmold method may be an efficient, industrial-scale way to tag red drum prior to release. Florida hatcheries are taking a more scientific approach to red drum enhancement compared to hatcheries in Texas, and Ransier hopes his results will help biologists in Texas understand how released drums are affecting wild populations.

   My internship at Mote introduced me to many facets of fisheries stock enhancement, and more importantly, the inner workings of long-term field studies at a large-scale marine laboratory. Mote is a business as much as it is a research institution, and budgeting, scheduling, and managing require as much time as the actual science. I was also shocked at how such extensive fieldwork was needed for a handful of data points. It is no wonder our knowledge of marine systems lags behind that of terrestrial environments. During my time in the field I recognized the importance of maintaining good relationships with local anglers and residents along the creeks, understanding the region’s natural history, and conducting numerous pilot studies before starting the long-term research. Solid methodology is critical to obtaining accurate results, as I became well aware of within my first week. This summer was an eye-opening learning experience that would not have been possible without your support. I thank the ES Mellon Grant for its generosity in enabling me to take advantage of such an opportunity.