Territoriality, Reproductive Behavior, and Parental Care in Gray Triggerfish, Balistes Capriscus, from the Northern Gulf of Mexico

Abstract

We documented spawning behaviors in gray triggerfish, Balistes capriscus (Gmelin, 1789), in June and July 2004–2007 on artificial reefs in the northern Gulf of Mexico, including territoriality, nest building, harem spawning, and parental care. Males were significantly larger than females and could be distinguished from females by size and dark charcoal coloration during the spawning season. Pre-fertilization dominant males were observed building and maintaining one to 13 demersal nests at particular reef sites, aggressively defending the immediate area surrounding the nests against other male gray triggerfish and other fishes, while attracting one to five females to spawn. Pre-fertilization females were observed frequently visiting and inspecting the newly constructed nest. Post-fertilization females stayed continuously on the nest guarding the eggs, and displayed a contrasting white and black color pattern, while fanning and blowing the eggs. Post-fertilization males continued to defend a territory immediately around the nest, visiting the female on the nest, and chasing other fish away. Actual spawning behavior was observed where a male and female tightly circled each other within the nest, with fertilized eggs produced immediately after this circling. Active nests with a guarding female and male were observed 28 times on 18 different reef sites. Mean number of eggs per spawning event was 772,415 from 13 active nests each with a guarding female. Observations of aggressive male behavior and sex ratios of single dominant male and up to five spawning-condition females indicate that gray triggerfish display harem spawning behavior.