Spawning-site choice by female Pseudolabrus celidotus (Pisces: Labridae) and its influence on the mating system

Abstract

1. The mating system and seasonal patterns of behaviour of the protogynous wrasse Pseudolabrus celidotus were studied for 2 years in a shallow reef habitat in north-eastern New Zealand, with the purpose of determining how site-specific spawning by females influences the behaviour and spawning success of terminal phase (TP) males. 2. Females were home ranging but made temporary trips into deeper areas during the breeding season solely for the purpose of spawning. Most TP males defended territories from other TP males, but nonterritorial, wide-ranging males commonly moved through the study area in the spaces between territories. The number of territories was highly variable, with only certain deeper sites being occupied consistently. Home ranges overlapped considerably with each other and with territories, but females were never actively confined to their ranges by TP males. 3. Spawning success of TP males was not related to body size, age, coloration, or territory size. Successful males were generally resident for longer periods, spent more time swimming, courting and behaving aggressively towards initial phase (IP) fish, and less time feeding during the spawning season. Testis weight: body weight ratios were positively correlated with spawning success. Spawning rate increased exponentially with the depth of the territory and was highest on territories with large patches of shelter centred on bare rock areas. 4. Experimental removal of TP males established that females were choosing particular sites to spawn at, and spawned only with TP males possessing these sites. Females presumably chose to spawn deep because egg-eating planktivorous fish were more abundant in shallow areas. The restriction of spawnings to areas adjacent to shelter sites suggests that females were vulnerable to predators during the spawning act. 5. The mating system is classified as ‘resource defence polygyny’ (Emlen and Oring 1977) since TP males defending preferred spawning sites accounted for the large majority of the spawnings. The influence of spawning-site selection on the territorial system is discussed.