Influence of death struggle on the structural changes in chub mackerel muscle during chilled storage

ABSTRACT: Chub mackerel (34–35 cm, approximately 500 g), which were caught by fishing with a rod and line at the Bungo Channel, Oita prefecture, were rested overnight in a fish preserve and either killed by decapitation (control group) or allowed to struggle in air for 30 min (struggled group). Muscle samples were excised every 4 h, and measurements on breaking strength and histological observations were done for both groups. The breaking strength of muscle in the control group was significantly higher than that in the struggled group, whereby a decrease in breaking strength was delayed for 12 h compared to the struggled group. Light microscopy showed space extension among muscle cells in association with a decrease in breaking strength. Especially in the struggled group, the extended area was larger and the difference in area was significant at the time when breaking strength showed a significant difference. Using electron microscopy, the extended area showed cut and/or disappeared collagen fibrils. From these results, it was demonstrated that struggling to death promoted the degradation of collagen fibrils and the weakening of connective tissue and, resultantly, led to the faster softening of muscle of chub mackerel.     

Shelf-Life of Spanish Mackerel (Scomberomorus commerson) from Northern Australian Waters

Abstract

The shelf-life of Spanish mackerel caught by line fishing in Northern Australian waters was evaluated. Spiked fish were stored in ice either headed and gutted or left uncut and subjected to sensory, nucleotide, pH, histamine and microbial analysts and the rigor pattern recorded. There was little difference between the two product forms. Rigor in uncut fish lasted for 14 ± 9.8 hours and in headed and gutted fish for 19.6 ± 16.3 hours. Spanish mackerel retained good sensory quality for up to 14 days. The bacterial load reached 105 cfu/g by 18 days. K values were low for most of the storage time, < 40%. Histamine levels did not develop more than 10 mg/kg during storage. The pH of Spanish mackerel did not change much even though bacterial levels become high.     

黄渤海蓝点马鲛个体生殖力的研究

本文根据1992～1993年黄渤海蓝点马鲛产卵期内采集的114个卵巢样品分析和组织切片观察，对其个体生殖力进行研究。结果表明，蓝点马鲛为分批排卵鱼类，在产卵期内排卵2～3次，个体绝对生殖力在45～5257千粒，个体组对生殖力和相对生殖力随年龄、体长、体重的生长逐渐增加，其中与年龄的关系最为密切。     

河南小尾寒羊产肉性能与羊肉品质的分析研究

就河南小尾寒羊的产肉性能和羊肉品质进行了分析研究。结果表明:河南小尾寒羊生长发育快,产肉性能好,肉质细嫩,肉味浓郁,6月龄的屠宰率较高。肌肉中的蛋白质含量较高,氨基酸含量丰富,其中的赖氨酸、异亮氨酸等达到或超过了标准蛋白质中的含量。     

Dual effects of reversed winter–spring temperatures on year‐to‐year variation in the recruitment of chub mackerel (Scomber japonicus)

To clarify the effects of temperature on the recruitment of chub mackerel (Scomber japonicus) in the North Pacific, we investigated the influence of winter surface temperature (WST) on spawners at the time of maturity around the spawning grounds and the influence of ambient spring temperature on larvae using estimated temperature (ET) obtained from particle tracking experiments. We found a significant positive correlation between ET approximately 10 days following hatching and the recruitment per spawning stock biomass (RPS) after 2000. The closer (more meandering) the Kuroshio Current (KC) axis was in relation to the spawning ground, the higher (lower) the spring surface temperature and the higher (lower) RPS was in the spawning ground. In contrast, WST inside KC near the maturity/spawning ground was significantly negatively correlated with RPS. A significant negative correlation between the temperatures in winter and spring was detected in the area after 2000, when the conditions of the Pacific decadal oscillation index and the stability of the Kuroshio Extension were synchronous, indicating that KC shifted northward during this time. The reversed temperature pattern was consistent with the winter–spring movement of KC axis in the offshore direction and was correlated with the winter–spring difference in the intensity of the Aleutian low. These results suggest that the annual variation in chub mackerel recruitment after 2000 was strongly affected by the combined effects of ambient temperature because of the reversal of conditions that occurred between winter and spring around the maturity/spawning ground, which was related to the KC path.     

Biochemical Properties of Pelagic Fish Proteins as Affected by Isolation Methods and Gel Properties by Heating Methods

The biochemical and gel properties of Pacific sardine and Pacific mackerel were characterized as affected by preparation and cooking methods. Four to eight times more salt soluble proteins were extracted from water-washed paste than fish protein isolate (FPI) paste. Higher total sulfhydryl content was measured in FPI, indicating the exposure of sulfhydryl groups during alkaline extraction. Comparing gel properties based on two cooking methods (slow and fast), the two pelagic fish proteins performed quite differently. Heating rate did not differentiate between surimi and FPI gels from sardine. However, mackerel exhibited higher texture values when using the fast cooking method, indicating the presence of high levels of proteolytic enzymes. Water-washed surimi gels were whiter than FPI for both species. Water retention ability appeared to be higher with mackerel than sardine, regardless of isolation and cooking method. Sodium dodecyl sulfate polyacrylamide gel eletrophoresis (SDS-PAGE) also supported a difference in processing chemistry and thermal behavior between two methods for protein isolation and cooking, respectively.     

浅谈资源租金理论及其在渔业中的应用

在综述地租理论、产权理论和公共物品外部性理论等自然资源租金理论的基础上,结合渔业资源的经济特性,提出了渔业资源租金的理论框架及其计算方法。渔业资源除稀缺性外,还具有再生性、洄游性、共享性等特性。由于具有共享性以及存在所有权和产权分离等问题,使得渔民在捕捞作业中只重视使用捕捞权利,而忽视对捕捞种类的养护,因此在自由入渔情况下捕捞生产中存在"市场失灵"和负外部性问题。针对上述问题,本文提出了在我国近海实施渔业资源租金管理制度的必要性和可行性;同时,借鉴国内外渔业资源租金研究方法,以近海鲐鱼(Scomber japanicus)资源为例,提出了鲐鱼资源租金计算的基本框架,为下一步深入研究打下基础。     

东南太平洋智利竹筴鱼栖息地指数的比较研究

根据2000~2007年度东南太平洋智利竹筴鱼的商业捕捞数据,结合海洋环境数据(SST,SSA,SSHG以及等温层深度),运用4种关联建模方法计算其栖息地指数,并使用Surffer 8.0软件绘制出HSI的空间分布图。通过2008年度的捕捞数据进行验证,结果表明4种模型的结果存在明显差异:采用算术平均法和几何平均法时,主要产量分布在0.6HSI0.9的区域;采用最大值法时,主要产量集中在0.8HSI1.0的区域;采用最小值法时,主要产量分布在0.3HSI0.6的区域。通过4种模型的验证结果比较,本文认为算术平均法和几何平均法能较好地反映东南太平洋智利竹筴鱼的中心渔场位置以及分布特征。