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Chub Mackerel Scomber Japonicus (chub + mackerel_scomber_japonicu)
Selected AbstractsEnvironmental effects on recruitment and productivity of Japanese sardine Sardinops melanostictus and chub mackerel Scomber japonicus with recommendations for managementFISHERIES OCEANOGRAPHY, Issue 4 2005AKIHIKO YATSU Abstract We compared a wide range of environmental data with measures of recruitment and stock production for Japanese sardine Sardinops melanostictus and chub mackerel Scomber japonicus to examine factors potentially responsible for fishery regimes (periods of high or low recruitment and productivity). Environmental factors fall into two groups based on principal component analyses. The first principal component group was determined by the Pacific Decadal Oscillation Index and was dominated by variables associated with the Southern Oscillation Index and Kuroshio Sverdrup transport. The second was led by the Arctic Oscillation and dominated by variables associated with Kuroshio geostrophic transport. Instantaneous surplus production rates (ISPR) and log recruitment residuals (LNRR) changed within several years of environmental regime shifts and then stabilized due, we hypothesize, to rapid changes in carrying capacity and relaxation of density dependent effects. Like ISPR, LNRR appears more useful than fluctuation in commercial catch data for identifying the onset of fishery regime shifts. The extended Ricker models indicate spawning stock biomass and sea surface temperatures (SST) affect recruitment of sardine while spawning stock biomass, SST and sardine biomass affect recruitment of chub mackerel. Environmental conditions were favorable for sardine during 1969,87 and unfavorable during 1951,67 and after 1988. There were apparent shifts from favorable to unfavorable conditions for chub mackerel during 1976,77 and 1985,88, and from unfavorable to favorable during 1969,70 and 1988,92. Environmental effects on recruitment and surplus production are important but fishing effects are also influential. For example, chub mackerel may have shifted into a new favorable fishery regime in 1992 if fishing mortality had been lower. We suggest that managers consider to shift fishing effort in response to the changing stock productivity, and protect strong year classes by which we may detect new favorable regimes. [source] Food habits of the silky shark Carcharhinus falciformis (Müller & Henle, 1839) off the western coast of Baja California Sur, MexicoJOURNAL OF APPLIED ICHTHYOLOGY, Issue 4 2010A. A. Cabrera-Chávez-Costa Summary The objective of this study was to establish the trophic niche of the silky shark and to determine the ecological role of this predator in the ecosystem close to Baja California. The trophic spectrum was analyzed from samples taken during summer and autumn (2000,2002) from the fishing camps of Punta Lobos and Punta Belcher on the western coast of Baja California Sur. A total of 263 stomach contents were analyzed (143 with food; 120 empty). The index of relative importance (IRI) showed that at Punta Lobos, silky sharks fed mainly on red crabs Pleuroncodes planipes (%IRI = 83%), whereas at Punta Belcher the main food item was the jumbo squid Dosidicus gigas (%IRI = 41%), followed by chub mackerel Scomber japonicus (%IRI = 33%). According to the Levin Index (Bi), the trophic niche breadth in silky sharks is low (Bi = <0.6), which means that silky sharks are specialist predators because they mainly consume three prey types: red crab, chub mackerel, and jumbo squid. The Shannon-Wiener Index indicated that all trophic categories at Punta Belcher (0.85,1.22) had lower diversity than at Punta Lobos (0.50,1.6), because the silky shark feeds more on tropical prey found close to Punta Lobos. The Morisita-Horn Index (C,) showed an overlap in the diet between the two areas analyzed and between sexes (C, = >0.6). The juveniles and adult females did not show any overlap. In the caloric analysis of the main prey, the jumbo squid (D. gigas) contributed the most calories to the silky shark diet (76%). [source] EFFECT OF SLAUGHTER METHOD ON DEGRADATION OF INTRAMUSCULAR TYPE V COLLAGEN DURING SHORT-TERM CHILLED STORAGE OF CHUB MACKEREL SCOMBER JAPONICUSJOURNAL OF FOOD BIOCHEMISTRY, Issue 5 2002KENJI SATO ABSTRACT The present paper demonstrates that a nonstntggling slaughter method can delay degradation of type V collagen in meat of chub mackerel Scomber japonicus and softening of the meat during postharvest chilled storage. The fish were slaughtered by piercing a knife into nape (nonstruggling method) or by leaving on ground (struggling method) and then stored in an ice box. Sensory study revealed that the postharvest softening of the meat was moderated at 4 and 8 h by the non-struggling slaughter method in comparison with the struggling method. On the basis of the specific solubilization of type V collagen and reduced tyrosine content in it, a cleavage of the nonhelical regions (telopeptides) of the type V collagen occurred during the chilled storage in the fish slaughtered by the struggling method. The degradation of type V collagen was also slower in the meat of the fish slaughtered by the nonstruggling method, which can be directly linked to the moderation of the postharvest softening. [source] | ||||||||||