GROWTH COMPARISON OF TWO COHORTS OF GULF KILLIFISH Fundulus grandis IN FRESHWATER PONDS AND SALINITY TOLERANCE POST- POND CULTURE

Brittany Chesser*, Christopher Green, and Peter J. Allen
 
Department of Wildlife, Fisheries, and Aquaculture
Mississippi State University
Mississippi State, MS 39762
bc1826@msstate.edu
 

Interest in culturing Gulf Killifish (Fundulus grandis), an estuarine species found along the Northern coast of the Gulf of Mexico and the Eastern coast of Florida, has been growing due to its use as a baitfish and its euryhalinity, allowing for culture in low salinities. However, information is limited on freshwater pond production and post-culture salinity tolerance, knowledge gaps that must be addressed before inland producers will adopt this species for commercial culture. Therefore, studies were conducted to determine if growth and survival were similar in cohorts stocked 4 weeks apart and if freshwater grow out affects salinity tolerance.     

A 12-wk freshwater pond growth experiment was conducted for two cohorts from 6/28/17- 9/18/17 and 7/31/17- 10/16/17, respectively. Each cohort had 3 ponds, stocked with a density of 25,000 fish/ha and evaluated for 12 weeks. Ponds were sampled every 4 weeks to monitor growth. Initial and final total lengths (TL) between cohorts did not vary significantly; however mean survival between the two cohorts did vary (Table 1). Possible reasons for variation include differences in pond water quality parameters, such as pH and hardness.

After the first cohort was harvested, 30 fish were randomly selected to evaluate salinity tolerance post-pond culture. Fish were randomly placed into individual containers at three salinity treatments of freshwater (FF: 0.5 ppt), brackish water (FBS: 8 ppt), and saltwater (FS: 33 ppt) and monitored for 120-hr. Fish in the FBS treatment were place into saltwater after a 6-hr acclimation period in the brackish water to mimic hauling tank conditions. Whole body moisture was significantly different between treatments, although other parameters were similar (Table 2). These studies show that cohorts will have similar growth if stocked several weeks apart, and freshwater grow out may affect salinity tolerance, although further studies are needed.