Longline Hook Selectivity for Branchiostegus japonicus (Houttuyn, 1782) and Dentex tumifrons (Temminck & Schlegel, 1843) in the East China Sea

Bottom longline fishing of red tilefish (Branchiostegus japonicus) is one of the most important commercial of fishing in the East China Sea. The present study aimed to investigate hook selectivity in B. japonicus and D. tumifrons, by means of experiments using three hook sizes (“J”: #15, #13 and #11) and was conducted in the East China Sea from June to August 2018. Altogether 602 B. japonicus fish and 858 D. tumifrons fish were caught. With respect to the size of the hook used, the total length-frequency varied significantly for both B. japonicus and D. tumifrons that were caught. The total length and four mouth parameters (upper and lower jaw length as well as height and width of mouth opening) of the two species showed a positive linear relationship. A logistic model created using the maximum likelihood method was used for elucidating hook selectivity; the best fit model with the minimum Akaike’s Information Criterion value was selected as the final model. The 50% selection lengths were 224.827 and 233.179 mm for B. japonicus; 201.461 and 202.603 mm for D. tumifrons using “J” #13 and “J” #11 hooks, respectively. To preserve the reproductive potential of younger fish in the stocks, the size of the “J” #13 hook was selected as the minimum hook size that should be used for the sustainable development of bottom longline fishing for B. japonicus and D. tumifrons.

A new and two known species of Hatschekia Poche, 1902 (Copepoda, Siphonostomatoida, Hatschekiidae) parasitic on Japanese fishes

Hatschekia laeopsi sp. nov., H. branchiostegi Yamaguti, 1939 and H. pagrosomi Yamaguti, 1939 are (re-)described based on specimens collected from the branchial lamellae of three Japanese fishes, Laeops kitaharae (Smith & Pope, 1906) (Pleuronectidae), Branchiostegus japonicus (Houttuyn, 1782) (Malacanthidae), and Dentex tumifrons (Temminck & Schlegel, 1843) (Sparidae), respectively. The free-living stages of H. branchiostegi are described for the species for the first time.

EFFECT OF ENDOGENOUS PROTEASES ON GELATION OF RED TILE FISH SURIMI

Red tile fish Branchiostegus japonicus meat degrades easily. In market, the small- sized fish is traded at a low price. Additionally, the population of red tile fish in the sea around Japan has reduced. Therefore, for effective utilization of small-sized red tile fish, the effect of endogenous proteases on heat-induced gelation of red tile fish surimi was investigated in the research. Fish gels from red tile fish surimi were prepared at different temperatures between 30 – 90 oC. After heating, the samples were cooled in ice water and then mechanical properties and SDS-PAGE patterns were analyzed. Homogenates prepared from the surimi were mixed with protease inhibitor solutions. The mixtures were incubated in water bathes at 40 or 60 oC. After heating, peptide contents in the supernatant and autolytic protein patterns were determined by the Lowry method and SDS-PAGE respectively. The surimi didn’t form heat-induced gels at 30 - 80 oC and SDS–PAGE showed that proteolysis markedly occurred. Addition of 1, 10-phenanthroline, benzamidine or SBTI prevented proteolysis. These results suggest that red tile fish surimi had extremely low gel- forming ability due to endogenous metalloprotease and trypsin-like serine protease. Keywords: Fish products, Gelation, Protease inhibitor, Surimi