Spawning dynamics of orange roughy,Hoplostethus atlanticus,in mid-slope waters of New Zealand

Synopsis The social and reproductive biology of the sand tilefish,Malacanthus plumieri (Malacanthidae), was studied at Glover's Reef, Belize, where this species occurs in colonies over sand-rubble flats. Individuals each occupy a home burrow refuge and a surrounding home range. Home range overlap among adjacent fish of the same sex is low, and individuals defend exclusive use of much of their home range against all conspecifics except mates (i.e., territoriality). Areas defended by males overlap the territories of up to 6 females; and male territory area is positively related to the number of female residents. Males maintain dominance over females within their territories by aggression, including intervention into some female disputes. Females spawn pelagically-dispersed eggs as frequently as every day. Each female spawns near her burrow, almost exclusively with the male whose defended area encompasses her territory (harem polygyny). Tilefish colonies therefore consist of a mosaic of female territories over which adjacent male territories are superimposed. Histological evidence and observation of behavioral sex change in one female revealed thatM. plumieri is capable of protogynous sex reversal. Females did not change sex in response to removal of one male. Occurrence of small transitional fish indicates that the onset of sex change is controlled by factors other than size-related social hierarchies within harems or colonies.     

Trichonotus halstead, a new sand-diving fish from Papua New Guinea

Synopsis Trichonotus halstead, family Trichonotidae, is described from 3 males and 4 females collected from a sand slope off the northwest end of Normanby Island, Papua New Guinea. It was part of a large population of 4 sympatric species of Trichonotus. The elaborately colored dorsal fin of the male, distinct among trichonotids, is brilliant gold anteriorly followed by a black patch, then a series of 8 to 40 conspicuous, black or dark brown spots that extend onto the upper caudal fin. The spines of the long dorsal fin are filamentous in the male and are numerous (VI to VIII, VII) in both sexes. This species lives in harems (1 male: 4 or 5 females) in well-defined territories and spends more than 80% of its day perched on sand. It feeds on benthic crustaceans and low drifting plankton. When disturbed, it dives into the sand where it also spends the night. It retires within 18 minutes after sunset and emerges within 11 minutes of sunrise. Mating takes place 6:00 h on the sand and the female then picks up the eggs into her mouth. There is evidence of gill-chamber brooding.     

Effects of size and sex on the social organization of reef-associated hogfishes,Bodianus spp.

Synopsis Three species of wrasses (Labridae) were examined in the field to determine the relative importance of size and sex in structuring social organization. The Spanish hogfish, Bodianus rufus, was characterized by stable dominance hierarchies that were linearly organized according to sex and relative size. Males were the largest and most-dominant individuals within discrete social groups of females (harems) whose dominance increased with body size. Dominance rank also increased with body size among both males and females of the Mexican hogfish, B. diplotaenia. Most encounters occurred between the sexes and males were clearly dominant over females. The vieja, B. eclancheri, differed from the other congeners since social interactions were not strongly patterned by either relative body size or sex. Hogfish dominance relationships appear to develop according to the manner in which males compete for females, including the formation of harems in permanent territories with single-male pairspawns (B. rufus), defense of temporary reproductive territories with single-male pairspawns (B. diplotaenia) or maximizing sperm production in multi-male group spawns (B. eclancheri).