Search Results - (Author, Cooperation:C. M. Bulman)

2011-07-23

American Association for the Advancement of Science (AAAS)

0036-8075

1095-9203

Biology

Chemistry and Pharmacology

Computer Science

Medicine

Natural Sciences in General

Physics

Animals ; *Aquatic Organisms ; Biodiversity ; Biomass ; Birds ; *Ecosystem ; *Fisheries ; *Fishes ; *Food Chain ; Mammals ; Models, Biological ; Oceans and Seas ; Population Dynamics

1095-8649

Blackwell Publishing Journal Backfiles 1879-2005

Biology

This study was designed to determine whether orange roughy reproduce throughout their distribution in Australian waters, and if so, whether commencement of spawning and length at maturity vary within the region. We found that females from four widely separated sampling areas reproduced in 1988, but that the onset of spawning and length at maturity were not the same in all the areas. In New South Wales, ovulation was finished by mid-June, and 50% of females were mature at 28 cm standard length (S.L.). On the other hand, females from eastern and western Tasmania and South Australia did not spawn until mid-July, and 50% of females from Tasmania were not mature until 32 cm S.L. Females from all areas had oocytes with yolk granules at least 5 months before ovulation. However, in the few months before spawning, some adult females from all areas had not undergone vitellogenesis or were resorbing all yolky oocytes. The best estimates of the proportion of these non-reproductive females were made in March and April, when the single batch of eggs to be spawned was clearly distinguishable, and before spawning aggregations had formed. In 1990 in eastern Tasmania, at the site of a major spawning aggregation, the best estimate of the proportion of non-reproductive fish was 45%. We suggest that scarcity of food, coupled with the cost of joining a spawning aggregation, may result in intermittent spawning in this long-lived species.

Electronic Resource

1432-1793

Springer Online Journal Archives 1860-2000

Biology

Abstract Diets of 15 species of demersal and pelagic fishes on the upper continental slope (420 to 550 m) were determined, based on samples taken every two months over 13 mo (April 1984 to April 1985) off eastern Tasmania. The calorific contribution of each prey item to the diets was determined. The fish could be divided into four trophic categories: pelagic piscivores, epibenthic piscivores, epibenthic invertebrate feeders and benthopelagic omnivores. Dietary overlap between the groups was low. The pelagic piscivores Apogonops anomalus, Trachurus declivis, Brama brama, Lepidopus caudatus and Macruronus novaezelandiae primarily consume the shelf-break myctophid Lampanyctodes hectoris; their diet is narrow, with a large overlap between species. The epibenthic piscivores Deania calcea and Genypterus blacodes both take a greater variety of prey, but have little dietary overlap. The fish feeding on epibenthic invertebrates, Coelorinchus sp. 2 and Centriscops humerosus, obtain most of their energy from benthic Crustacea and Ophiuroidea, supplemented with Lampanyctodes hectoris; the diet is broad, with little overlap. Among the benthopelagic omnivores (Cyttus traversi, Coelorinchus sp. 4, Lepidorhynchus denticulatus, Neocyttus rhomboidalis, Helicolenus percoides, Epigonus denticulatus and E. lenimen), most diets are broad and show slight overlap. All but E. denticulatus consume significant quantities of Lampanyctodes hectoris as well as Crustacea, particularly Polychaeta, Euphausiacea and Pyrosoma atlanticum. Seasonal changes in diet occurred in G. blacodes, T. declivis, Lepidopus caudatus, Coelorinchus sp. 4, Lepidorhynchus denticulatus, H. percoides, E. denticulatus and E. lenimen; these were related to changes in abundance of particular prey species, not to alterations in feeding habits. Only three species, Lepidopus caudatus, Coelorinchus sp. 2 and H. percoides, showed significant diel feeding periodicity. Ontogenetic dietary changes were evident in Cyttus traversi, Coelorinchus sp. 2, Lepidorhynchus denticulatus and H. percoides. Cyttus traversi and H. percoides progressively changed from crustaceans to fish as their size increased. The diets of size classes within species showed little overlap, except for Lepidorhynchus denticulatus, which eats chiefly euphausiids and Lampanyctodes hectoris at all sizes. In addition to describing the diets and trophic relationships of 90% of the fish biomass, the results emphasize the importance to the entire fish community of mesopelagic food resources, particularly Lampanyctodes hectoris. Many benthopelagic species undertake extensive vertical migrations in search of prey, thus playing a major role in the transport of energy from midwater regions to the benthos of the continental slope.

Electronic Resource

1432-1793

Springer Online Journal Archives 1860-2000

Biology

Abstract The age, growth and mortality of the lanternfish Lampanyctodes hectoris (Gunther) were investigated by examining the otoliths, length-frequency data, and seasonal abundance of fish collected from continental slope waters of eastern Tasmania between April 1984 and June 1985. Although L. hectoris can live to 3 yr old, it has a high annual mortality (79%) and few live past their first year. Growth, described here by a variation of the Von Bertalanffy model, takes place mainly in the first six months of life and only during late spring and summer. The hypothesis of daily deposition of primary growth increments in myctophids was supported by comparing the back-calculated birth dates of daily-aged individuals of L. hectoris with the spawning season of this species.

Electronic Resource