Algae as first food for cod larvae, Gadus morhuaL.: filter feeding or ingestion by accident?

Abstract

Cod larvae. Gadus morhua L., 2 4 days posthatch, were fed different species of algae in order to evaluate both rates and mechanisms of ingestion. The results were compared with cod larvae feeding on a natural assemblage of algae in a lagoon. Small algae (Nannochloris atomus Butcher, 1 4 pm) were found to enter the larval gut in accordance with drinking rate. In contrast, the cod larvae concentrated larger algae [Dunaliella salina (Dunal) Teodor. 6 10 pm] in the gut at rates from 492 to 7251 times the drinking rate. D. salina was captured in the slits between the visceral arches, and increased activity when the algae was added indicate that the cod larvae are active filter feeders during early larval stages. In the gut of cod larvae from the lagoon the fraction of algal material with diameter larger than 8 pm was 39.2% in 7-day-old larvae while, in 12-day-old larvae it had decreased to 12.6%. The most conspicuous characteristics of gut content in the youngest larvae were green spheres (10 pn) and a naked dinoflagellate (20 p). Short chains of the diatom Skeletonemu cosrarum (Greville) Cleve were also frequently found.

Development of hatchery technology for the silver pomfret Pampus argenteus (Euphrasen): effect of microalgal species on larval survival

“…These papers discuss the effect of microalgae on the nutritional and behavioural aspects of fish larvae. Some fish larvae take up substantial amounts of microalgae during the initial days after hatching, as has been reported in cod (Meeren 1991) and halibut (Reitan, Bolla & Olsen 1991). This may support the idea that microalgae are used as a direct food source at the start of feeding.…”

Use of the microalgaNannochloropsis occulatain the rearing of newborn longsnout seahorseHippocampus reidi(Syngnathidae) juveniles

“…Microalgae are often added to intensive culture systems for marine fish larvae, as these organisms generally enhance growth and survival. This posi-tive effect has been found in several species of marine fish (Naas et al 1992 Meeren (1991), microalgae may also be ingested incidentally and thereby serve as a direct source of nutrients, stimulating the synthesis of endogenous enzymes and providing exogenous enzymes that may assist in the digestion of the prey (Hjelmeland, Pedersen & Nilssen 1998). Such factors are important to individuals with an underdeveloped digestive system (Kolkovski 2001).…”

“…A number of authors report that microalgae provide essential nutrients, such as vitamins and fatty acids, to the live feed offered in the early stages of development of marine fish (Brown, Jeffrey, Volkman & Dunstan ; Reitan, Rainuzzo, Oie & Olsen ; Lee & Ostrowski ; as examples). According to Meeren (), microalgae may also be ingested incidentally and thereby serve as a direct source of nutrients, stimulating the synthesis of endogenous enzymes and providing exogenous enzymes that may assist in the digestion of the prey (Hjelmeland, Pedersen & Nilssen ). Such factors are important to individuals with an underdeveloped digestive system (Kolkovski ).…”

Investigations into the causes of early larval mortality in cultured summer flounder (Paralichthys dentatus L.)

“…This trial began on 3 DAH, as in the previous trials, but was extended to last until 14 DAH to allow for the possible extended survival due to any nutritional value (Van der Meeren, 1991;Stottrup, 1994) of algae in the unfed , algae added, controls. The culture methodology of experiment 1 was followed with some changes: a) the number of larvae per bowl at the start of the trial was increased to 150 to account for sampling during the increased length of the trial, and b)larvae were measured on days 3, 10, and 14 after hatch.…”