Search

White trevally Pseudocaranx dentex is a high-value carangid fish species that is only cultured in Japan under full lifecycle aquaculture conditions. To make the reproductive process successful and efficient, sexual phenotyping of broodstock is essential, and this has conventionally been practiced via examination upon abdominal compression. However, in certain cases, sexual phenotyping is not successful due to unsuccessful sperm or semen collection, which leads to misclassification of the phenotype. This study identified the male characteristic DNA sequence of P. dentex. The pectoral fins of eight male and eight female 6-year-old F3 generation broodstock fish were utilized for male sex hormone quantification to determine each sex phenotype. The same fish DNA samples were subjected to bulked-amplified fragment length polymorphism (AFLP) screening, and a male characteristic AFLP DNA fragment of 227 bp in size was identified. A male characteristic fragment was also confirmed by second amplification when it was performed individually. All eight males used for screening carried the AFLP fragment, while none of the eight females did. AFLP was conducted for all 40 broodstock, and it was determined that all 24 putative males were AFLP positive, and 4 of the 16 putative females were AFLP positive. These results indicate that P. dentex may have a male characteristic DNA polymorphism. The nucleotide sequence of the male characteristic fragment showed high homology to Atlantic horse mackerel Trachurus trachurus chromosome 5, and the sequence did not have clear homology to known coding genes. Further studies are required to identify the sex-determining gene of P. dentex in the vicinity of the DNA sequence identified in this study. [ABSTRACT FROM AUTHOR]

Fish meal (FM) used in fish farming is prepared by steaming, squeezing, defatting, drying and crushing raw fish material. However, how drying affects protein digestibility has not been systematically studied. Herein, we evaluate the effect of additional heating of FM on in vitro FM protein digestibility and growth performance of white trevally (Pseudocaranx dentex) juveniles. We heated conventional steam‐dried Chilean FM from 50–200°C for 1 h to prepare additionally heated FM (AHFM). In‐vitro AHFM protein digestibility started to decrease significantly above 150°C, along with substantial reduction in the protein digestion speed. Five isonitrogenous/isolipidic experimental diets were prepared by substituting different proportions of FM with AHFM produced by heating FM to 180°C. In‐vitro protein digestibility and digestion speed of the experimental diets decreased linearly with increasing AHFM content. After a 33‐d feeding trial, the final bodyweight, specific growth rate, weight gain and feed efficiency of white trevallies decreased linearly and/or quadratically with increasing dietary AHFM levels. These findings indicate that in vitro protein digestibility of AHFM decreases linearly at temperatures above 150°C, and the growth and feed efficiency of white trevallies are negatively affected by dietary inclusion of AHFM processed at 180°C. [ABSTRACT FROM AUTHOR]

Three experiments were conducted to elucidate the most suitable rearing light intensity during the ontogenetic changes in white trevally (Pseudocaranx dentex) larvae. In Experiment 1, larvae were reared under 1000, 3000 or 9000 lx. At 10 days post hatching (dph), larval growth was significantly higher in the 1000 lx treatment than in the other treatments. In Experiment 2, larvae were reared under 30, 100, 300, 1000, 3000, and 9000 lx, and 300 lx was revealed to be the most suitable light intensity for larval growth and survival until 10 dph. However, light intensities higher than 1000 lx may promote larval growth after 10 dph when the larval retina has developed prior to the metamorphic stage. In Experiment 3, larvae were exposed to increasing light intensities (i.e. from 300 lx to 1000, 3000 and 9000 lx) from 10 to 18 dph. Our results indicated that the most suitable rearing light intensity was 300 lx during the first week of development and at the commencement of feeding, and between 1000 and 3000 lx when the larvae approached the metamorphic stage. The rearing light intensity should, therefore, be adapted throughout the ontogenetic development of white trevally to promote larval growth and production efficiency. [ABSTRACT FROM AUTHOR]

Specimens of the three new fish species were recorded during 2015 and 2016 in the River Neretva Estuary. These species are: White trevally, Pseudocaranx dentex (Bloch and Schneider, 1801), Pilotfish, Naucrates ductor (Linnaeus, 1758) and White grouper, Epinephelus aeneus (Geoffroy Saint–Hilaire, 1817). The characteristics of caught specimens and their history of records in Adriatic Sea are described. Potential impact of new species invasion in the Neretva Estuary as a major Eastern Adriatic nursery habitat is discussed.