28 paginas, 2 tablas. Special Issue: Basic and Applied Aspects of Aquaculture Nutrition: Healthy Fish for Healthy Consumers. The definitive version is available at www.blackwell-synergy.com

Live feeds for early stages of fish rearing.

The onset of exogenous feeding in marine fish larvae

Despite the fact that the suitability of copepods as live prey for marine fish larvae is now well established, their use in aquaculture remains sporadic. Although of lower nutritional value, the relative ease of production of rotifers (Brachionus spp.) and Artemia nauplii continues to ensure their predominance. Studies in the literature have highlighted differences in the levels and ratios of fatty acids, lipid classes and pigments between copepods and traditional live prey. Such differences may have important consequences for fish larval nutrition. The consequences of poor nutrition during fish larval development may be obvious, for example deformities or malpigmentation, but in many cases may be obscure, as in affects on temperature tolerance or growth during later life stages. In some aquaculture systems, copepods are cultured in large quantities in outdoor, extensive or semi-intensive units. Intensive-rearing systems for copepods require further development. However, it is now established that intensive rearing on monoalgal diets does not result in severe deterioration of the nutritional value of the copepods, at least in terms of their highly unsaturated fatty acid (HUFA) content. In some cases, the provision of copepods for a short period of time during the larval stage is sufficient to ensure normal development. However, it remains to be demonstrated that the extra costs involved result in increased profits as a result of higher percentages of normally pigmented juvenile fish, improved growth and survival and reduced incidence of disease. This paper reviews the advances in production systems for copepods, their nutritional value as live prey for fish and their present and potential use in aquaculture.

The elusive copepods: their production and suitability in marine aquaculture

Production and use of copepods in marine fish larviculture.

The potential of tropical paracalanid copepods as live feeds in aquaculture

Use of Copepod Nauplii During Early Feeding Stage of Grouper Epinephelus coioides.

The osteological development of elements forming the oral cavity was examined in early stage larvae of the grouper,Epinephelus coioides, from hatching to 242.5 hours after hatching. By the time of initial mouth opening, at 54 hours after hatching, the fundamental elements, composed of the trabecula, some components of the lower branchial and hyoid arches, the quadrate and symplectic-hyomandibular cartilages, maxilla and Meckel's cartilage, had appeared. No further elements were observed until 165 hours after initial mouth opening, except some components in the lower branchial arch and head region. The appearance of new elements and initial ossification of existing cartilage occurred thereafter, but all elements related to feeding either had not appeared or had not started ossifying until 188.5 hours after initial mouth opening. Based on the morphology and developmental modes of these elements, the feeding mode of grouper larvae was considered to be “sucking/grasping.” However, the appearance and ossification of elements occurred slowly, with no transitional phase from sucking to grasping modes of feeding being observed during the study; such delayed development of the feeding-related bony elements was considered to be a cause of the difficulty in rearing early stage grouper larvae.

Why is grouper larval rearing difficult?: an approach from the development of the feeding apparatus in early stage larvae of the grouper,Epinephelus coioides

Larvae of red-spotted grouper, Epinephelus coioides, were reared in outdoor tanks with nauplii of copepods (mainly Pseudodiaptomus annandalei and Acartia tsuensis)and/or rotifers, Brachionus rotundiformis. Grouper larvae successfully started feeding on early stage nauplii even though their abundance was as low as approximately 100 individuals 1−1 and showed better survival and growth thereafter compared to those fed with rotifers only. Incidence of feeding reached 100% on day 4 when nauplii were available and only on day 9 when rotifers were given alone. Larvae seemed to be poor feeders at the onset of feeding, attempting to capture any food organisms in the tank water. Selective feeding ability of larvae started from day 4 and the larvae then preferred to feed on medium- and large-size nauplii rather than on rotifers as they grew. Larvae appeared to have a better chance at surviving in the presence of early stage nauplii, which were probably caught more easily than rotifers.

Preliminary investigation of feeding performance of larvae of early red-spotted grouper, Epinephelus coioides, reared with mixed zooplankton

Food Selection of Early Grouper, Epinephelus coioides, Larvae Reared by the Semi-intensive Method

The osteological development of the feeding apparatus was examined in early stage larvae of laboratory-reared seabass,Lates calcarifer At initial mouth openings 40 hours after hatching, the larvae were equipped with the fundamental elements forming the oral cavity, such as the trabecular roof, the lower branchial and hyoid arches forming the floor, the quadrate and symplectic-hyomandibular cartilages making up the sides, and the maxilla and Meckel's cartilage bordering the jaws The cleithrum appeared almost simultaneously The mechanics of creating a negative pressure in the oral cavity, which results in a “sucking” mode of feeding, were elucidated from these elements During a period from 50–60 to 100–110 hours after initial mouth opening (HAMO), new elements such as the premaxilla and jaw teeth appeared, and the ossification of existing elements started The new elements apparently enabled the larvae to “grasp” food organisms, in addition to the already existing and increasing sucking ability, from 100–110 HAMO

Atsushi Ohno

Papers

Use of Copepod Nauplii During Early Feeding Stage of Grouper Epinephelus coioides.

Why is grouper larval rearing difficult?: an approach from the development of the feeding apparatus in early stage larvae of the grouper,Epinephelus coioides

Preliminary investigation of feeding performance of larvae of early red-spotted grouper, Epinephelus coioides, reared with mixed zooplankton

Food Selection of Early Grouper, Epinephelus coioides, Larvae Reared by the Semi-intensive Method

Osteological development of the feeding apparatus in early stage larvae of the seabass,Lates calcarifer