Peculiarities of the male urogenital apparatus of two grunt species (Teleostei, Haemulidae)

An unusual testicular structure in the white grunt, Haemulon plumieri , and the French grunt, H. flavolineatum , and a urinary exocrine gland in H. flavolineatum are described. The testes of both species are comprised predominantly of efferent ducts, with spermatogenetic tissue restricted to the gonadal periphery. The epithelial cells of the efferent ducts produce glycogen which may serve a role in the storage and nutrition of sperm. The urinary gland is a male accessory gland thought to be associated with reproduction. The gland is mesonephric in origin and the epithelial cells of the gland produce mucins which may be involved in intraspecific chemical communication.     

Mating system of the rockfish, <Emphasis Type="Italic">Sebastiscus marmoratus</Emphasis> as revealed by DNA fingerprinting

The mating system of the viviparous rockfish, Sebastiscus marmoratus was studied using aquarium mating experiments and paternity testing by DNA fingerprinting. Individually specific DNA fingerprints were produced and the paternal relationships determined with the use of the restriction enzyme HinfI and the DNA probe (CAC)₅. Two types of mating experiments, multiple-male and single-male, were set up to investigate the effect of male sizes on their mating success, as determined by number of females fertilized. Male size was positively and significantly related to mating success in the multiple-male situation in which male–male interaction was present, but not in the single-male situation in which no male–male interaction was involved. Females produced one to seven batches of larvae, and all batches from individual females had identical paternity. Most females were fertilized by a single male but one case of multiple paternity was detected. The laboratory study suggested the principal mating system of S. marmoratus to be promiscuity, although multiple mating by females was uncommon.     

Mating system in a small pelagic spawner: field case study of the mandarinfish,Synchiropus splendidus

Environmental Biology of Fishes - Mating systems in fishes are extremely diverse, ranging from monogamy to multiple polygamous forms, some of which include alternative male mating tactics within...     

Habitat Association and Social Structure of the Chocolate Hind, <Emphasis Type="BoldItalic">Cephalopholis boenak</Emphasis> (Pisces: Serranidae: Epinephelinae), at Ping Chau Island,Northeastern Hong Kong Waters

Synopsis The chocolate hind, Cephalopholis boenak, is the smallest and last remaining grouper of any abundance in Hong Kong waters. We investigated its habitat association and social structure to understand its sexual pattern and seek possible approaches to protect this species. Juveniles and adults are distributed in the same habitat and strongly associated with corals, in particular, Pavona decussata when available, for settlement and residence. Social groups of C. boenak are relatively small with a single male, one or two smaller females, and varying numbers of sexually inactive individuals (which are mature but sexually inactive, or juvenile). Males defend their boundaries by chasing neighbouring males and have significantly larger home ranges than females. Males visit females and sexually inactive individuals at one or more specific locations, consistently following similar paths. There was a positive linear correlation between body size and home range in individuals ≥90 mm TL. We observed male courtship in the reproductive season, within his home range during the late afternoon. Spawning behaviour is not associated with any particular moon phase and may occur more than once within the reproductive season. Although C. boenak is a diandric, protogynous hermaphrodite, primary and secondary males could not be distinguished by behavioural patterns in the field. Population management of this species should include habitat protection.     

The threat of fishing to highly fecund fishes

The last decade has witnessed a growing awareness that fishes can not only be severely overfished but could also be threatened with extinction through over-exploitation. Among commercially important species, those particularly at risk are large and slow to mature, iteroparous and may have sporadic recruitment. The threat of extirpation or extinction may be greater if species are particularly valuable, have a limited geographical range, are part of mixed-species fisheries, or are distributed solely within areas of intense fishing activity. Significantly, there is little empirical or theoretical basis for hypothesizing that highly fecund species are any less at risk than those of low fecundity, as is often assumed. Indeed, the use of fecundity in estimating reproductive output in long-lived, highly fecund, pelagic egg-producing species, may be deeply flawed. A general resistance to accepting that fecund marine fishes could become endangered through exploitation stems from poor understanding of population dynamics, especially in the early post-settlement phase, coupled with assumptions of fishery models that ignore critical components of life history theory. Moreover, faith in the ability to manage exploited species effectively leads to the perception that severe declines are management, rather than conservation, issues. The growing list of threatened marine species and a realization of the many factors that place them at risk indicate the need to be precautionary about the possibility of extinction, and about the criteria used to assess such risk, with important implications for research, monitoring and management.     

Evaluating the use of spawning success to estimate reproductive success in a Caribbean reef fish

Observations on egg batch production by known female Stegastes partitus and the fates of those egg batches within the nests of known males revealed that spawning success was not a reliable predictor of hatching success and, hence, reproductive success because of high egg batch mortality. Moreover, while numbers of eggs per batch increased with increasing female length, both inter- and intra-individual variation in batch size was considerable, demonstrating that spawning events cannot be considered equivalent. These two findings indicate that spawning success cannot be assumed to provide a direct quantitative substitute for a measure of reproductive success in this benthic spawning reef fish.     

Sexual development and sexuality in the Nassau grouper

Hermaphroditic sexual patterns are widespread among teleosts and are especially characteristic of certain perciform families. Among the most diverse groups of hermaphroditic species are the groupers, hamlets and sea basses of the family Serranidae. Like other groupers, the epinepheline serranid, Epinephelus striatus , the Nassau grouper, has long been assumed to exhibit monandric protogyny (a form of hermaphroditism in which all males derive from adult females by sex change). Histological and demographic data, however, indicate that the sexual pattern of this species is not monandric, and that, unlike other group species, the juveniles pass through a bisexual stage of gonadal development. Sexuality in the Nassau grouper is essentially gonochoristic, with potential for sex change. The combination of bisexuality and gonochorism is previously undescribed in the serranids.