EGG PRODUCTION IN GULF KILLIFISH Fundulus grandis AT VARYING ENVIRONMENTAL SALINITIES  

Salinity plays a significant role in the distribution of aquatic animals and is particularly important for esturine fishes where salinity can change often. The Gulf killifish (Fundulus grandis) occupies a wide range of salinities and is distributed within the northern Gulf of Mexico and extreme southern Atlantic coast. As a secondary result from the recent Deepwater Horizon oil spill, freshwater was flushed into the Gulf to potentially push oiled-water away from coastal habitats. The freshwater introduced to these systems and future alterations due to freshwater inputs have the potential to alter important physiological conditions in fishes.  Even though the Gulf killifish can survive in an extreme range of salinities, 0 to 76 ppt, this preliminary study seeks to determine differences in reproductive performance as it relates to altered salinity.  

Three different recirculating systems, were painted with black aquatic, fish-safe paint to crate different salinities for sexually mature Gulf killifish.  Each system was maintained at a different salinity with three tanks in each system representing 3, 12, and 22 ppt. Once the paint cured for a week, the tanks were hosed down to ensure the paint was dry and then filled with water from their system. Four female and three male gulf killifish were placed in each 30 L tanks, for a total of 63 fish being used in the experiment.   Female size ranged between 12-20 g while males were below 18 g.   The fish were fed once daily, Monday through Friday, and received constant aeration throughout the experiment.  An automatic light timer was used to keep the fish on 14 hours of light and 10 hours of darkness to simulate photoperiod during the spawning months for this species. The fish acclimated to their tanks and new salinities for a week and then each tank received spawning substrate placed inside a PVC pipe.

Eggs were collected from the spawning substrate twice a week and data collection recorded the total numbers of egg as well as the numbers of fertilized and unfertilized eggs from each salinity treatment.  The results of this preliminary study will be used to highlight spawning in this species across a wide range of salinities.  We anticipate that this species might produce differences in egg output at lower and intermediate salinities.