摘要:

The continuing increase in numbers of toxic algal species coupled with increased incidences of blooms of these species presents a constant threat to public health worldwide. Traditionally, only filter‐feeding molluscs that concentrate these toxic algae are considered in monitoring programs for paralytic (PSP), diarrhetic (DSP), neurotoxic (NSP), and amnesic (ASP) shellfish poisons; however, increasing attention is being paid to higher‐order consumers such as carnivorous gastropods and crustaceans. This review summarizes data on accumulation of phycotoxins by “non‐target”; species frequently consumed by humans, and stresses the importance of including such species in routine monitoring programs, especially in regions where nontraditional spedes are being harvested.

ISSN:1064-1262    

DOI:10.1080/10641269509388565

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Many ecologists and aquaculturists view crayfish as either detritivores or herbivores. The nutritional importance of detritus and plant material, seemingly confirmed by examination of stomach contents is exaggerated. Examination of stomach contents emphasizes indigestible residues, for example, plant fragments and detritus, while neglecting the ingestion of easily digestible soft‐bodied metazoans. The few comparative studies that have measured the assimilation and metabolic use of ingested items reveal animal protein to be the chief substance promoting rapid growth. Crayfish are not indiscriminate omnivores; in fact, they demonstrate a predilection for animal protein. Crayfish rank among the chief carnivores found in lakes and streams. To completely understand their role, crayfish should be viewed from two perspectives: that of an individual attempting to complete its life cycle, and the collective functioning of a population in the ecosystem, which can produce a serious ecological impact. While searching for and ingesting animal protein, they can ingest large amounts of herbaceous and detrital materials. As sources of animal protein are exhausted, crayfish become facultative herbivores. After reaching high densities, their extended foraging activity can modify habitat, for example, destruction of macrophyte beds, algal mats, etc. In an extreme situation, they can seriously reduce or even eliminate other animals and plants from the ecosystem. Hence, crayfish often act as keystone predators and serve as major conduits of energy and materials in complex food webs.

ISSN:1064-1262    

DOI:10.1080/10641269509388566

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

A review of published scientific and hatchery production data concerning the feed training of largemouth bass and their culture to advanced fingeriings is presented. The review concludes that largemouth bass can be trained successfully to accept a prepared diet The best training diet is a semimoist formulation. The optimal training size is 1.0 g 05 to 50 mm) and stocking density is 4 to 8 kg/m3of water. Bass fry between 10 and 20 mm can be trained to a prepared diet, but with a lower success rate and greater expense. Training success is greatest using northern strain largemouth bass fingeriings. In a 10‐to 14‐d training period, approximately 70% of the fish stocked will be trained. Approximately 65% of the fingeriings trained to a semimoist pellet can be converted to a dry, floating pellet suitable for pond grow‐out Fish growth rate during training is approximately 0.05 g/d.

ISSN:1064-1262    

DOI:10.1080/10641269509388567

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor