Collection and transportation of young of the year weakfish for use in laboratory experiments

Young of the year (YOY) weakfish, Cynoscion regalis, were captured off the Delaware shore of Delaware Bay using trawl nets and beach seines during late July and August 2009 for use in planned temperature and salinity dependent growth studies. While aboard the trawling vessel fish were held in a 133-L holding and transport vessel with oxygen supplied to the water from a cylinder. A small container was used to separate desirable fish from debris and other species brought up in the otter trawl. No less than four water exchanges were done throughout the day with one last exchange performed before heading back to the boat ramp at the end of the day. Dissolved oxygen, salinity and temperature were recorded for the holding tank and the bay bottom before heading back to the boat ramp as well. Fish were transported to the Delaware State University Aquaculture Research and Demonstration Facility and immediately transferred to acclimation tanks at a density of 50 individuals per 360-L tank. Fish captured each day were quarantined and treated with Nitrofurazone at 9 mg/L for six days. On the morning of the seventh day 80 % of the total volume in the tank was siphoned, and tanks were then refilled with water from the recirculating system and the drains opened to complete the recirculating loop. Mortality was highest within 24 hours of bringing the fish into the laboratory with a final survival of 56 %. Once enough YOY weakfish are captured, they will be stocked at 20 individuals per tank for subsequent research trials. Fish will be randomly stocked into 18 360-L tanks and individual tanks will then be randomly assigned to one of three treatments. The goal of this study will be to measure growth rates of C. regalis in closed environments with salinities (year 1) and temperatures (year 2) above the historical averages for Delaware Bay.