Evidence of homing of black rockfish Sebastes inermis using biotelemetry

ABSTRACT: The black rockfish Sebastes inermis is one of the most important fishery species along the coast from southern Hokkaido to Kyushu, Japan and is often found in rocks and Zostera areas. We conducted biotelemetry using coded ultrasonic transmitters to clarify the movement of the black rockfish that inhabited the seawall of the Kansai International Airport. We released 25 black rockfish at two points. One was the airport seawall and the other was side shallows off the Sensyu district. Seventeen black rockfish returned to their capture site after release. We used the V -test to determine whether the direction of movement was random or orientated. The black rockfish moved at random along the seawall within some hours after release ( P  > 0.05). Four hours after release, they moved to their home site intentionally ( P  < 0.0025).     

Morphological aspects of feeding and improvement in feeding ability in the early larval stages of red sea bream Pagrus major

The present study examined the appearance, ossification and growth of the bones that form the oral cavity in early larval stages of laboratory reared red sea bream ( Pagrus major ) for 380 h after hatching. The fundamental elements of the oral cavity appeared 11 h after initial mouth opening (HAMO). Development in the red sea bream, based on the osteological development of the feeding apparatus, was divided into three phases following the first feeding (24 HAMO; mean total body length 3.3 mm). The first phase was the early sucking phase (24 to 80–100 HAMO; approximately 3.9 mm), during which the head and bones increased in size. The intensified sucking phase (to 200–220 HAMO; approximately 4.9 mm) was defined by the appearance of new structural elements and a continued enlargement of the head and bones. Finally, during the transition phase (beyond 300 HAMO; approximately 5.6 mm), larvae used grasping as well as sucking to feed, new elements appeared, ossification began, size increased and teeth were acquired. As the larvae advanced through these three phases, the ability to feed by sucking was enhanced by the appearance and growth of new bones. The developmental phases appear to be linked to the transition from endogenous to exogenous nutrition resources under laboratory rearing conditions and to diversification in the size and components of wild food organisms.     

HCG与LHRHa对雌性蜂巢石斑鱼产卵期间生理变化的影响及比较

选取日本冲绳地区雌性蜂巢石斑鱼为对象,描述与分析了HCG与LHRHa对该鱼催产效果的差异及注射后所引起的性腺发育变化和排卵相关的性类固醇变化,希望能为蜂巢石斑鱼的人工繁殖提供可靠的理论基础,以及在实践生产中的重要参考。结果表明,HCG与LHRHa均显著促进了决定排卵的性成熟诱导物质MIS的释放以及鱼的产卵; 产卵后的蜂巢石斑鱼雌二酮E2的水平显著下降,验证了蜂巢石斑鱼卵巢发育及产卵随月亮周期变化的周期性; 在渔业生产中注射催产药物前,确定对象鱼卵泡发育阶段对于提高催产成功率十分重要。在LHRHa注射组,完成卵黄化的蜂巢石斑鱼催产效果最佳,卵黄化早期的鱼不产卵; HCG对卵泡发育初期的蜂巢石斑鱼的催产效果优于LHRHa,但催产效果仍不理想,而对于完成了卵黄化鱼的催产效果不如LHRHa。结合LHRHa的其他优势,本研究认为在具备检验鱼体卵巢发育阶段实验技术的条件下,更加推荐LHRHa作为雌性蜂巢石斑鱼的催产药物。     

A three-dimensional numerical model for a mariculture nitrogen cycle: case study in Shizugawa Bay, Japan

A numerical model is developed for mariculture management, which consists of: (1) calculation of spatial distribution of PON (particulate organic nitrogen) using simulated current, (2) calculation of spatial distribution of DO (dissolved oxygen), (3) calculation of DON (dissolved organic nitrogen), (4) calculation of spatial distribution of DIN (dissolved inorganic nitrogen), and (5) calculation of the horizontal distribution of accumulated matter which is supplied by deposits from the mariculture of fish. This model is capable of calculating the detailed spatial distribution of PON, DON, DIN and DO by dividing the bay into many grid points. It also takes into consideration the effects of feed and fish in each raft, and the loading of DIN from rivers. The model is applied to Shizugawa Bay, in Miyagi Prefecture, Japan. The model elucidated the oxygen cycle among ecological compartments. The amount of dissolved oxygen supplied by photosynthesis is much greater than the consumption through respiration by fish and all other conditions for mariculture of fish are favourable in this bay.