PS 4-52
Nearshore larval fish assemblages in a Caribbean estuary
Estuaries are an important ecosystem where freshwater and marine environments meet. These estuaries can provide nursery habitats for some fish species, but are also important for amphidromous fish species, specifically the Sirajo Goby, Sicydium plumieri. However based on the importance of this species there is a lack of adequate research on the development and early life cycle of the Sirajo Goby. It is unclear whether these larval fish migrate back to freshwater from a lunar cue, the third quarter of the lunar cycle, or from freshwater inputs from the river mouth. Nearshore surface water sampling was conducted in the river mouth of the Rio Grande de Arecibo in Arecibo, Puerto Rico. Bongo plankton nets were towed at speeds of 5-6 kph on the surface of the water for 3-4 minutes. Each sampling session consisted of three trolls, one close to the shore, one farther out, and one in between the two. Samples were collected from each troll and larval fish were later identified. It was noted whether each troll was performed within the freshwater plume.
Results/Conclusions
Our results of the study consisted of a large variety of different larval fish species, with over fifty percent belonging to the Gobiidae family, twenty-five percent belonging to the Achiridae family, and the remaining thirty percent was made up of the Centropomidae, Blennioidei, and Eleotridae families. Of the Gobiidae family, our results showed that thirty-five percent were amphidromous and sixty-five percent were non-amphidromous. However, even with these results, the small n value makes it difficult to strong conclusions from. Nevertheless, we did take some exciting footage of what looked like groups of larval fish, quite possibly those of the Siraho Goby species. The Sirajo Goby is inherently valuable to the local culture and economy, and it will be increasingly important to the future management of the species to have answers to the current questions, such as where the larval fish are travelling when they are on their way back to the river mouth, what cues are helping them find their way back, and how sustainable is the current rate of harvest done by the local fishermen.