No abstract

No abstract

No abstract

The predation pressure on the siphons of the bivalve Nuttallia olivacea by the juvenile stone flounder Platichthys bicoloratus in the Natori River estuary, Miyagi, was estimated from both sides of the predator–prey relationship to analyze the specific relationship in which predators remove a part of the prey. Feeding experiments determined the feeding rate required to achieve the growth of juvenile stone flounders in the field. A juvenile cropped siphon tips at a mean of 56 per day from March to early July. The siphon tips that a juvenile consumed in a season amounted to 6375 pieces (6.2 g). In terms of predation, the duration since the last cropping in the field from the regeneration of cropped siphons was analyzed. The mean cropping rate of 0.211 times a day per clam in an area of intensive predation indicated that a clam was cropped 25.8 times (22.1 mg) in a season by fishes. The mean cropping rate by juvenile stone flounders was estimated to be 0.160 times a day. Of the 25.8 croppings, 19.5 (16.9 of the 22.1 mg) could be attributed to juvenile stone flounders. The results proved that a juvenile stone flounder preyed on approximately 370 clams in a season.

This study examined age and growth of Japanese flounder Paralichthys olivaceus off the Pacific coast of northern Japan, and determined whether the growth patterns of male and female fish in northern (40-41°N) and southern (37-38°15′N) waters differ. In total 8095 specimens were collected between January 1999 and December 2005. Zonation consisting of opaque and translucent bands on the otolith was evident. Within each opaque band a thin and clear check (ring mark) was observed in all specimens examined. Monthly change in the frequency of appearance of a ring mark on the outer margin of the otolith indicates that ring marks form between July and August. The von Bertalanffy growth model showed a sexual dimorphism in growth, as females grew faster and reached a larger size than males. The growth patterns obtained by tracking the observed total length for monthly collections showed a rapid increase in total length between August and October. Spatial variation in the growth pattern of male and female fish between northern and southern waters was evident, as southern fish were significantly larger than northern counterparts during 1.25-3.00 years post hatch.

In Fukushima Prefecture, one million hatchery-reared juvenile Japanese flounder Paralichthys olivaceus have been released annually in the stock enhancement program since 1996. A community-based management system is used for this flounder fishery, where fishers pay 5% of their annual landings to operate the stock enhancement program. Also, since 1993, fishers have consented not to catch flounder <30 cm total length to maximize economic gains from the investment in stock enhancement. Our fish market surveys revealed that released flounder annually contributed an additional 30-90 tons to the catch. However, the economic efficiency of stocking has reduced since 1996, which has been largely attributed to a decline in fish price and recapture rate. Another problem is that the population dynamics of wild flounder have never been considered during implementation of the stock enhancement program. The occurrence of a dominant year-class of wild flounder causes a dramatic increase in landings and removes the need to release hatchery-reared juveniles. However, the program cannot be easily terminated because it plays important roles in having fishers recognize the importance of fishery management. It is a difficult but important realistic problem concerning how to make the stock enhancement program more flexible and effective.

A series of novel azulene-1 carboxylic acid derivatives 28-30, azulene-1 sulfonic acid sodium salts 41a-c, and related compounds were synthesized. These compounds were tested for TXA2 receptor antagonistic activity. The inhibitory concentrations (IC50) of these compounds for vascular contraction (TXA2 tau receptor) and platelet aggregation (TXA2 alpha receptor) induced by (15S)-15-hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5(Z),13(E)- dienoic acid (U-46619) were obtained. Azulene-1-sulfonic acid sodium salts 41a-c were over 3 times more potent than azulene-1-carboxylic acids 28-30. The most potent compound, 41b was 4 orders of magnitude more potent than a TXA2 antagonist, BM13,177, in inhibiting vascular contraction (tau receptor) and had an IC50 of 9.0 x 10(-10) M. Compound 41b was also found to be a tau receptor selective antagonist (IC50 of contraction/IC50 of aggregation = 378) and to have no TXA2 synthetase inhibitory activity at concentrations up to 10(-4) M and no partial agonistic activity at concentrations up to 10(-5) M in rabbit aorta (tau receptor) and up to 10(-4) M in rabbit platelet-rich plasma (alpha receptor). In a radioligand binding assay using rabbit gel-filtered platelets, compound 41b had a high-affinity binding for the TXA2 receptor. In an in vivo study, compound 41b inhibited U-46619-induced sudden death in mice at a dose of 0.3 mg/kg and its duration of action was over 8 h when administered orally at 3 mg/kg.

No abstract