Abellán-Martínez, E. (Emilia)

Arizcun-Arizcun, M. (Marta)

García-Alcázar, A. (Alicia)

English

Abellán-Martínez, Emilia

García-Alcázar, Alicia

Arizcun-Arizcun, Marta

Digital.CSIC

EFFECT OF PREY DENSITY ON THE FIRST FEEDING OF SHI DRUM (UMBRINA CIRROSA) LARVAE

Repositorio Institucional Digital del IEO

EFFECT OF PREY DENSITY ON THE FIRST FEEDING OF SHI DRUM (UMBRINA CIRROSA) LARVAEE. Abellán, A. García-Alcázar and M. ArizcunInstituto Español de Oceanografía. Centro Oceanográfico de Murcia. Ctra. de la Azohía s/n. Puerto de Mazarrón. Murcia. SpainE-mail: emilia.abellan@mu.ieo.es IntroductionThe shi drum, a member of the Sciaenidae family, is considered a good candidate for Mediterranean aquaculture because of its high growth rate, good adaptability to culture conditions and high market price. Although some studies on the culture of shi drum have been carried out, no experiment aimed at defining the optimal supply of live prey at the critical period of first feeding of larvae has been designed. In order to design a feeding protocol for shi drum larvae, optimal rotifer concentration, the best timing for startfeeding and the moment that larvae are able to hunt Artemia nauplii, have been determined. Also, the point of no return (PNR) has been defined. Materials and methodsLarvae were obtained by natural spawning from broodstock adapted to captivity. Three replicates per treatment were performed in 15 l. cylindroconical tanks with soft aeration, in which 450 larvae were placed. Rotifers were administered for the first time to larvae in concentrations of 1, 2.5, 5, 7.5, 10 and 12.5 at the ages of 2, 3, 4, 5 and 6 days post hatching (dph) at a temperature of 20±0.5ºC. To each tank, together with rotifers, Tetraselmis phytoplankton was administered at a concentration of 50 000 cells.mlˉ¹. Larvae were allowed to feed for 6 hours, then preserved in 4% formalin solution for later study of their stomach contents to count the amount of rotifers ingested.150 larvae from each of the treatments were examined. The percentage of fed larvae and the number of rotifers ingested per individual larva were determined. To define the point of no return (PNR) of the larvae during starvation they were fed with 12.5 rotifers.mlˉ¹ from 2 dph to death for starvation.In order to establish the most suitable time to start feeding with Artemia nauplii, 400 shi drum larvae were placed in each 15 l. tank at the ages of 5, 6, 7, 8, 9 and 10 dph. All trials were set up in triplicates. Larvae, previously fed rotifer, were fed Artemia at a concentration of 2 nauplii.mlˉ¹. Two hours later, stomach contents of 30 larvae/tank were examined to determine the percentage of fed larvae. To compare the results the analysis of variance (ANOVA) was applied.ResultsAt a temperature of 21±0.5ºC, death by starvation occurs within 6 dph. The time to reach the PNR (when rate feeding of larvae is half its maximum initial value) is 4.48 dph (Figure 1).Figure 1. Larval feeding rate after different starvation days. Shi drum larvae, in all cases, start feeding the second day, the moment their mouths open (Figure 2). From that moment on, the larvae were able to catch the food at any of the tested densities. The highest percentages of fed larvae can be seen on the third day for the larvae fed with 12.5 rot/ml. In general terms, the rate of fed larvae increased with increasing prey density. Independently of the prey density, the number of fed larvae is significantly higher (p<0.05) on day 2 and 3 than on day 4, 5 and 6.  The number of ingested rotifer on day 3 is significantly higher (p<0.05) than on the rest of days. Figure 2. Percentages of fed larvae (mean ± SEM) and average number (mean ± SEM) of rotifers ingested per larva, receiving different concentrations of rotifers at 20±0.5ºC. From the age of four days old, larvae have practically lost the ability to catch the prey so that by days five and six they are not able to feed.Larvae feed Artemia nauplii from day 5 dph (40%) and at day 10 all most 100% of them fed Artemia. AcknowledgementsThis study was supported by the research projects 15275/PI/10 of the Seneca Foundation. Comunidad Autónoma de Murcia.

http://www.repositorio.ieo.es/e-ieo/bitstream/10508/2097/1/Abellan1.doc

EFFECT OF PREY DENSITY ON THE FIRST FEEDING OF SHI DRUM (UMBRINA CIRROSA) LARVAE

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