Reproductive Behavior in Abudefduf saxatilis: The Relationship Between Nest Location, Brood Size and Aggression

This study investigated the reproductive behavior of the Caribbean Sergeant Major, Abudefduf saxatilis. The aim was to identify the possible relationships between nest locations, brood size and aggression rates in males when guarding their eggs. Surveys were conducted using Sergeant Major nesting aggregations located on a group of 5m deep mooring blocks on Bonaire, Netherlands Antilles. As brood size increased, aggression rates (attacks/ min) also significantly increased (R2 = 0.0492). The benefits of protecting the brood from intruders may outweigh the risks to the individual for large broods. Aggressiveness can also be a behavioral trait preferred by females when choosing a nest to lay their eggs. Therefore males who exhibit greater aggression may be more reproductively successful. Aggression rates significantly increased for individuals nesting on or near the upper level on the mooring blocks (t= 0.00045; p<0.05). Although the number of other fish visiting the different areas of the mooring blocks was not counted, the general impression was that the upper portions of the blocks were subject to more traffic from other fish. The helps support the finding that aggression rates increased for nests located in the higher positions because these males may have been given more opportunity to defend their eggs. No significant relationship was found between nest location and brood size. Nest location did not appear to be important in determining patterns of female egg-laying suggesting that male choice, rather than nest choice is the driving factor.

This student research was retrieved from Physis: Journal of Marine Science III (Spring 2008)19: 31-35 from CIEE Bonaire.