Soft-bottom benthic assemblages and levels of contaminants in sediments and biota at Gray's Reef National Marine Sanctuary and nearby shelf waters off the coast of Georgia (2000 and 2001)

A series of studies was initiated to assess the condition of benthic macroinfauna and chemical contaminant levels in sediments and biota of the Gray’s Reef National Marine Sanctuary (GRNMS) and nearby shelf waters off the coast of Georgia. Four key objectives of the research are (1) to document existing environmental conditions within the sanctuary in order to provide a quantitative benchmark for tracking any future changes due to either natural or human disturbances; (2) to examine broader cross-shelf spatial patterns in benthic fauna and sediment contaminant concentrations and to identify potential controlling factors associated with the observed patterns; (3) to assess any between-year temporal variability in benthic fauna; and (4) to evaluate the importance of benthic fauna as prey for higher trophic levels. Such questions are being addressed to help fulfill long-term science and management goals of the GRNMS. However, it is anticipated that the information will be of additional value in broadening our understanding of the surrounding South Atlantic Bight (SAB) ecosystem and in bringing the knowledge to bear on related resourcemanagement issues of the region. We have begun to address the first three of these objectives with data from samples collected in spring 2000 at stations within GRNMS, and in spring 2001 at stations within the sanctuary and along three cross-shelf transects extending from the mouths of Sapelo, Doboy, and Altamaha Sounds out to sanctuary depths (about 17-20 m). This report provides a description of baseline conditions within the sanctuary, based on results of the spring 2000 survey (Section II), and uses data from both 2000 and 2001 to examine overall spatial and temporal patterns in biological and chemical variables within the sanctuary and surrounding inner-shelf environment (Section III). (PDF contains 65 pages)

Effects of human chorionic gonadotropin (HCG), toad and Clarias pituitary hormogenates on spawning in the catfish: Clarias Lazera (C. and V.) and Clarias anguillaris (Linne)

Experiment on induced spawning of Clarias lazera and C. anguillaris using human chorionic gonadotropin (HCG) freshly prepared toad and Clarias pituitary hormogenates were carried out. Clarias pituitary hormogenates induced spawning in C. lazera and C. anguillaris at dosage levels of 0.27-0.46 mg/150 g body weight or 2 glands/fish of equivalent weights. HCG induced spawning in C. anguillaris at 500 i.u/500 g body weight but failed in C. lazera. Toad pituitary was not successful at even a higher dosage level of 0.60 mg/150 g body weight. The implications of these results are discussed. Spawning occurred in the HCG (and Clarias pituitary treated females in less than 12 hours after injection and subsequent examination of ovaries of the spawned fish showed incomplete spawning. Furthermore, fertilization occurred, following spawning in the piscine pituitary hormone treated male and female fish but failed in the HCG (treated pair. A mean fertilization rate of 50-90% was recorded. Possible explanations of these observations are advanced. The hatching time of 24-48 hours and a mean hatching rate of 75-90% were recorded. A high larval mortality of up to 95% was observed in the post yolk-sac stag after 8 days. The need for the development of appropriate larval food for Clarias species in culture practice is stressed

Manipulation of chromosomes in fish: review of various techniques and their implications in aquaculture

Human ingenuity has made it possible to advent the chromosome manipulation techniques to produce individuals with differing genomic status in a number of fish using various causal agents such as physical shocks (temperature or hydrostatic pressure), chemical (endomitotics) and anesthetic treatments either to suppress the second meiotic division shortly after fertilization of eggs or to prevent the first mitotic division shortly prior to mitotic cleavage formation. This results in the induction of polyploidy (triploidy and tetraploidy), gynogenesis (both meiotic and mitotic leading to clonal lines) and androgenesis in fish population. The rationale for the induction of such ploidy in fish has been its potential for generating sterile individuals, rapidly inbred lines and masculinized fish, which could be of benefit to fish farming and aquaculture. In this paper, these are critically reviewed and the implication of recently developed chromosome manipulation techniques to various fin fishes is discussed.