Remote video analysis of an unusual fish life-history combination: nest-building, paternal care, and protogyny in a seabream

Abstract

Seabreams from two genera, Spondyliosoma and Spicara, have a unique life-history that combines nesting, paternal care, and protogyny. Whereas protogyny is a common sexual system among seabreams, all, except Spondyliosoma and Spicara spp., are broadcast spawners. We describe the nesting behaviour of Spondyliosoma emarginatum as a basis for analysing this unusual life-history combination. We remotely filmed males on a nesting site with over 80 nests in South Africa. It has been postulated, based on morphometric data and general observations, that males invest heavily in nest-building, courtship, and egg-guarding, although these behaviours had never been documented. Energy intensive behaviours, including the clearing of invertebrate invaders (7 counts h−1) and fanning of nests (86 counts h−1), remained constant before and after the appearance of eggs. Males spent 79.2% of their time on the nest. The remainder was spent chasing other fish species and neighbouring males (12 counts h−1) and avoiding predation. Paired spawning events proceeded in batches. Nest take-overs and sneaker male attempts were recorded. The young leave the nest immediately after hatching. Males did not feed during the 67-day nesting period. Energetic costs of nest maintenance, starvation, and predation risk explain the condensed (relative to other seabreams) 51-day spawning season. S. emarginatum meets the requirements of the SAM as nest defence requires large male body size. Their short lifespan classifies Spondyliosoma spp. as opportunists, which may explain their success across a wide range of biogeographic zones from the cold temperate North Atlantic to the subtropical western Indian Ocean. These characteristics set Spondyliosoma spp. apart from the bulk of the seabreams, which are long-lived, broadcast-spawning, periodic strategists.