Nassau grouper (Epinephelus striatus) are an iconic fish both in The Bahamas and throughout the Caribbean. These large fish have come to characterize the regions’ reefs, however, because of overfishing during their yearly spawning aggregations, (see previous posts here and here), the Nassau grouper is considered endangered throughout its range. The Bahamas have done a better job than most countries in preserving Nassau grouper populations by placing seasonal bans on their harvest during spawning season. In a recent paper published in Coral Reefs we show that protecting Nassau grouper during their breeding season may be beneficial for both Nassau grouper populations and the reefs that host the aggregations.
In previous posts (e.g. here and here) we have discussed the important role fish play in maintaining the productivity of nearshore ecosystems by recycling nutrients stored in the tissue of other plants and animals, (where they are unavailable to plants), into a dissolved, available form. In this paper we estimated the rate of nutrients supplied by the Nassau grouper at and aggregation occurring off of Little Cayman, Cayman Islands. Our estimates of nutrient supply rate were larger than nearly all other published sources of nutrients on reefs. We also compared rates of nutrient supply on the Little Cayman aggregation to our best estimate of nutrient supplied by the (now fished out) Cat Cay aggregation, which was the first scientifically described Nassau grouper aggregation. In 1972 the Cat Cay aggregation was estimated to host nearly 100,000 fish, over 90,000 more fish than the largest aggregations left today. While a decrease of this magnitude is obviously disconcerting for the continued existence of the iconic Nassau grouper, our results show that it may also have consequences for nutrient cycling, and therefore productivity, of the reefs which host spawning aggregations.