Study on behavioral characteristics of wild and hatchery-reared red tilefish

Organized by Graduate School of Informatics, Kyoto University ; JSPS Bangkok Liaison Office ; Japanese Society of Bio-logging Science ; Informatics Research Center for Development of Knowledge Society InfrastructureDecember 13-15, 2004, Imperial Tara Hotel, Bangkok, ThailandThe diel activity of red tilefish Branchiostegus japonicus was studied using two different methods : analysis of biotelemetry records and video observation. We have acquired the biotelemetry tracking records of the red tilefish which were released in Maizuru Bay and tracked from January 2003 to February 2004. The records ware compared to the time of sunrise and sunset, the duration of sunshine, and the lunar cycle, which may influence on light conditions. Whilst the fish showed diel activity, the fish changed their behaviors along with the time of sunrise and sunset; the fish probably moved out of their burrows in the daytime and retreated into the burrows at night. We could not find a clear relationship between the behavior and the other two factors. In the laboratory, the behavior of one hatchery-reared individual was recorded by video for five days in the experimental tank where the light condition changed periodically over 24 hours. The fish was more active in the light periods (550 lx) compared to in the dark periods (0 lx). Since the results from the two methods probably compliment one another, further experiments using the two methods will reveal the detailed behavior of red tilefish

Food availability before aestivation governs growth and winter reproductive potential in the capital breeding fish, Ammodytes japonicus.

Capital breeders develop gametes by using energy that was stored before the spawning season. Energy is allocated to growth and reproduction, and limited food availability affects the balance of energy allocation, especially in fish that mature within a year, such as western sand lance (Ammodytes japonicus). This species aestivates without feeding until winter spawning and utilize energy stores that were accumulated prior to aestivation for maturation and spawning. This study aimed to evaluate the growth, energy storage, maturation rate, and reproduction of A. japonicus in response to food availability before aestivation. We conducted laboratory experiments in which young-of-the-year A. japonicus were fed at rates of 4% and 1% of their body weight per day; assigned as high and low ration groups, respectively. In June, body length was found to be significantly larger in the high ration group than in the low ration group, but the somatic condition did not differ significantly between the groups. Maturation rates and average fecundities were 1.0 and 6297 in the high ration group and 0.8 and 2251 in the low ration group, respectively. These results indicate that food availability before aestivation strongly governs the reproductive potential of A. japonicus, and suggest the involvement of mechanisms in the inter-annual recruitment variation in sand lance species

A new type of fish diet, non-fish meal extruded pellet for yellowtail, Seriola quinqueradiata

A non-fish meal diet using plant and/or animal protein materials for yellowtail, Seriola quinqueradiata was developed. Three kinds of non-fish meal diets and a control diet containing 50% fish meal were processed. In the non-fish meal diets, the fish meal was replaced with commercially available plant or animal materials and supplemented with taurine and other ingredients for maintaining palatability. These diets were fed to one year old yellowtail (body weight: 753±96 g) in net cages. No significant differences in growth, daily weight gain, daily feed rate, feed conversion ratio and protein efficiency ratio were observed among fish given the diets. Non-fish meal diets were processed in a factory and their biological characteristics were studied such as uptake, stomach evacuation rate, and disease resistance. In addition, the diet palatability of each substitute protein source for fish was examined and ingredients that enhanced palatability of the non-fish meal diets were identified. Non-fish meal diets have the potential to support the growth of one year old yellowtail

Quantitative Trait Loci (QTL) Associated with Resistance to a Monogenean Parasite (<i>Benedenia seriolae</i>) in Yellowtail (<i>Seriola quinqueradiata</i>) through Genome Wide Analysis

<div><p>Benedenia infections caused by the monogenean fluke ectoparasite <i>Benedenia seriolae</i> seriously impact marine finfish aquaculture. Genetic variation has been inferred to play a significant role in determining the susceptibility to this parasitic disease. To evaluate the genetic basis of Benedenia disease resistance in yellowtail (<i>Seriola quinqueradiata</i>), a genome-wide and chromosome-wide linkage analyses were initiated using F₁ yellowtail families (n = 90 per family) based on a high-density linkage map with 860 microsatellite and 142 single nucleotide polymorphism (SNP) markers. Two major quantitative trait loci (QTL) regions on linkage groups Squ2 (<i>BDR-1</i>) and Squ20 (<i>BDR-2</i>) were identified. These QTL regions explained 32.9–35.5% of the phenotypic variance. On the other hand, we investigated the relationship between QTL for susceptibility to <i>B. seriolae</i> and QTL for fish body size. The QTL related to growth was found on another linkage group (Squ7). As a result, this is the first genetic evidence that contributes to detailing phenotypic resistance to Benedenia disease, and the results will help resolve the mechanism of resistance to this important parasitic infection of yellowtail.</p></div

Multiple QTL model mapping results of the significant markers for Benedenia disease resistance in linkage group 2 and 20 in family A.

<p>Locus; marker name, LOD; Lod scores, % Var; percent of variance explained, Effect; estimated effect. Squ(linkage group)F; F is dam allele in female linkage group. Values in bold are LOD max in peak of each QTL marker position and each value.</p

Localization of significant markers for Benedenia disease resistance in linkage group Squ2F and Squ20F with family A.

<p>Squ(linkage group)F; marker distance in female map. (A) Squ2F, (B) Squ20F. Map positions and LOD scores are based on a simple interval mapping QTL analysis using the software MapQTL 5. Marker absolute map distances are given in (cM). 95% confidence probability LOD support interval was indicated as Gray bold line. Horizontal lines across each plot indicate LOD siginificance threshold, <i>P_g</i>; genome-wide significance threshold.</p

Between fish size and number of parasites in pairwise Pearson correlations.

<p>Values in bold are different from a significance level <i>P</i> = 0.001.</p

Simple interval mapping results of the fish sizes in linkage group 7 and 17 in family A.

<p>Locus; marker name, LOD; Lod scores, % Var; percent of variance explained. Effect; estimated effect. Squ(linkage group)F; F is dam allele in female linkage group. Values in bold are LOD max in peak of each QTL, marker position and each value.</p

Significant markers for Benedenia disease resistance multiple-QTL model mapping in linkage group Squ2F and Squ20F with family A.

<p>Squ(linkage group)F; marker distance in female map. (A) Squ2F, (B) Squ20F. This figure was described using by MapQTL 5.</p