摘要:

The economics of most modern aquaculture operations require that animals be cultured at high densities. A consequence of high‐density aquaculture is the increased probability that the animals will be exposed to elevated concentrations of nitrogenous wastes, particularly ammonia and nitrite. Ammonia toxicity is dependent primarily on the concentration of ammonia and the pH of the environment High concentrations of ammonia will decrease survival, inhibit growth, and cause a variety of physiological dysfunctions. Nitrite toxicity is dependent on the concentration of nitrite and, in many species, the concentration of chloride in the water. Nitrite toxicosis is characterized by reduced survival and growth, methemoglobinemia, and other physiological dysfunctions. Both ammonia and nitrite act as stressors in that they stimulate the release of corticosteroid hormones into circulation. Elevated concentrations of circulating corticosteroids have been linked to impaired immune function and, consequently, decreased disease resistance. Aquaculturists who wish to limit losses and remain competitive must recognize the specific detrimental effects as well as the probable immunosuppressive effects of ammonia and nitrite.

ISSN:1064-1262    

DOI:10.1080/10641269409388560

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

A diverse assortment of organisms is cultured under specific pathogen‐free (SPF) conditions. These include livestock and poultry, certain laboratory animals, and a few aquatic species. The procedures for cultivating these organisms are specialized according to the biology of the pathogen and the requirements of the animal cultured. This article contains an overview of these culture methods with the goal of identifying principles, techniques, and background information of potential use in the establishment of SPF aquaculture centers.

ISSN:1064-1262    

DOI:10.1080/10641269409388561

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Throughout the nineteenth and first half of the twentieth centuries, fleets of fishing vessels 20 to 35 ft in length sailed daily, weather permitting, from the South Carolina port of Charleston to coastal offshore waters. Sailing out of sight of land with no navigational aids, the fishermen's reputation as skilled navigators, and a source of high‐quality fresh fish during periods when refrigeration was unavailable, won them the respect and admiration of the community. Known as the “mosquito fleet”; and sailing as a unit, their main objective was the blackfish banks located up to 10 to 15 mi offshore. Depending on season and depth, commonly captured inshore species included whiting(Menticirrhus americanus), summer trout(Cynoscion regalis), croaker(Micropogonias undulatus), and bluefish(Pomatomus saltatrix); deeper‐water species included blackfish (Centropristis striata), porgy (Calamus leucosteus), bastard snapper(Pagrus pagrus), and grunt(Haemulon plumieri). Reports of the fleet fishing blackfish banks 40 mi offshore were probably exaggerated based on today's knowledge of blackfish bank locations. In the 1880s, the fleet consisted of about 50 vessels and over 300 fishermen who organized a union to care for the sick and bury the dead. Storms posed the most serious threat with a single squall in 1901 resulting in the loss of 15 fishermen. A total of 57 died at sea from 1900 to 1935. During the early 1930s, the Charleston fleet continued to enjoy a high community standing and held boat races in Charleston Harbor as part of the Fourth of July festivities. A1940 hurricane damaged nearly the entire fleet, an event from which it never recovered. World War II and new opportunities aboard larger commercial fishing vessels with refrigeration lured younger fishermen away from the mosquito fleet lifestyle. Those who remained used speedboats and began to fish singly, more often focusing their attention on crabs and other inshore species. Mr. Arthur Wright, the last “commodore”; of the mosquito fleet, died in 1973.

ISSN:1064-1262    

DOI:10.1080/10641269409388562

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Biology and habitat use of mountain whitefish (Prosopium williamsoni)throughout its range are reviewed for its spawning; early developmental, hatching, and emergence; and underyearling, yearling, and subadult to adult feeding and migratory stages. About44%of the 112 relevant publications pertain to U.S. populations (California, Nevada, Utah, Wyoming, Montana, Idaho, Oregon, “Washington), about 42% to British Columbia populations, and the remainder to Alberta or other populations. About 63% of the studies have been published since 1970. There are surprising gaps in essential life history and other biological aspects of the species, which severely limit development of techniques for habitat compensation and improvement arising from impacts on habitat by impoundments, pipeline and road construction, forestry and mining activities, as well as on the populations themselves by recreational fisheries. Nevertheless, a series of specific needs and recommendations for habitat compensation and improvement are given.

ISSN:1064-1262    

DOI:10.1080/10641269409388563

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor