The distribution of the ectoparasite fauna of Sebastes capensis from the southern hemisphere does not correspond with zoogeographical provinces of free-living marine animals

Aim We examined the ectoparasite fauna of Sebastes capensis over almost all its geographical distribution range (Chilean, Argentinean and South African coasts) to determine (1) whether the ectoparasites of this host show a zoogeographical pattern and, if so, (2) how this pattern is related to known zoogeographical patterns for free‐living organisms. Location Fish were captured from 20, 24, 30, 33, 36, 40, 45 and 52° S along the Chilean coast; 11° S on the Peruvian coast; 43° S on the Argentina coast; and 34° S on the South African coast. Methods From April to September 2003 and from April to August 2004, 626 fish were captured. The parasites were collected using standard parasitological techniques. At the component community level, zoogeographical distribution patterns were evaluated using cluster analysis. At the infra‐community level, patterns of similarity in parasite composition among localities were investigated with multivariate discriminant analyses. Results The ectoparasite fauna of S. capensis consists of six species distributed along the whole of the Chilean coast. Four other species are distributed only within the transitional zone between the northern warm temperate region (Peruvian faunistic province), extending from Peru to the northern Chilean coast up to c. 30° S, and the cold temperate region (Magellanic faunistic province). The component communities from latitudes 30 to 40° S showed higher ectoparasite species richness, while localities on the margins of the geographical range showed lower species richness. Cluster analysis indicated a grouping of localities consistent with the transitional zone. Argentina and South Africa always emerged as separate localities. Main conclusions The ectoparasite communities of S. capensis do not follow a distributional pattern concordant with the known biogeographical zones for invertebrates and/or fish along the south‐eastern Pacific. Therefore their ectoparasite fauna is not useful as a zoogeographical indicator, although it does allow us to distinguish the transitional zone of the south‐eastern Pacific. On a more extended geographical scale, it is possible to distinguish the ectoparasite communities of S. capensis in the south‐eastern Pacific (as a whole) from those of Argentina and South Africa.     

Analysis of Microsatellite DNA Polymorphisms in Rockfish Sebastes thompsoni and Application to Population Genetics Studies

Population differentiation and relationships among 6 natural rockfish populations collected from northern coastal seas around Japan were assayed using microsatellite DNA loci. Seven loci examined were polymorphic in all populations. The number of alleles per locus ranged from 6.7 to 9.3, and the average of observed and expected heterozygosity ranged from 0.63 to 0.68, and from 0.66 to 0.69, respectively. The observed genotype frequencies at each locus were almost in agreement with Hardy-Weinberg expectations with two exceptions (P < .05). The allele frequencies of 16 population pairs were significantly different (P < .05). Genetic distance (D _A ) between 6 populations ranged from 0.03 to 0.08. According to a neighbor-joining tree generated from the D _A values, the 6 populations fell into 3 clusters. These clusters were correlated with the geographical positions of each population; larval dispersions due to water current were also found to have an effect on these results. Received May 2, 2000; accepted July 17, 2000.     

Techniques for live capture of deepwater fishes with special emphasis on the design and application of a low-cost hyperbaric chamber

A cost effective, simple, portable hyperbaric chamber was constructed from polyvinyl chloride to aid in the collection of adult rockfishes Sebastes sp. to hold as broodstock. This system was designed to recompress fishes quickly once brought to the surface on hook and line, and to allow for decompression over a period of days. The hyperbaric chamber is capable of continuous stable operation at <1 033 515 N m⁻² and can accommodate fishes up to 91·4 cm in length and 26·8 cm in diameter. Pressure in the chamber is maintained by a Goulds Booster pump that delivers continuous pressure and supplies sea water at a rate of 3·8 to 7·6 l min⁻¹ to as many as four chambers. The hyperbaric chamber operated very effectively and allowed successful decompression of 12 cowcod Sebastes levis captured at depths of 90·2 to 146·3 m.     

Lipid class dynamics during development in early life stages of shortbelly rockfish and their application to condition assessment

Lipid class dynamics and the relationship between weight and length were analysed during early life stage (ELS) development in wild populations of shortbelly rockfish Sebastes jordani to investigate their utility in a condition or nutritional status assessment. Analyses from more than 3000 field-captured shortbelly rockfish indicated little variation in weight for a given length and provided limited application in the assessment of condition. The fractionation of total lipids into individual classes revealed trends in lipid metabolism throughout development. These trends were described best using a stage-specific regression model, since Sebastes show defined early life history transitions. Among developmental stages, triacylglycerols (TAG) and polar lipids (PL) were the dominant lipid classes and cholesterol (CHOL), sterol/wax esters, and nonesterified fatty acids were found in lower concentrations. In the preflexion stage, low concentrations and constant levels of TAG along with the combined influence of endogenous and exogenous sources of energy compromised the use of TAG as an index of nutritional status. However, during flexion through juvenile stages, TAG levels increased indicating an accumulation of energy reserves with development, thus providing a valid indicator of nutritional status in later stages. Large fluctuations in PL concentrations during development suggested complex metabolism which may be due to changes in cell volume and cell membrane proliferation with development as well as catabolism. CHOL declined in larval stages, then remained constant with increasing size through the juvenile stage, negating its use as a normalizer for variations of mass in a TAG/CHOL ratio prior to juvenile transformation. This study provides the first documentation of lipid dynamics during early life stages following parturition in a marine viviparous teleost.     

Marine reserves can enhance ecological resilience

The goals of ecosystem‐based management (EBM) include protecting ecological resilience, the magnitude of a perturbation that a community can withstand and remain in a given state. As a tool to achieve this goal, no‐take marine reserves may enhance resilience by protecting source populations or reduce it by concentrating fishing in harvested areas. Here, we test whether spatial management with marine reserves can increase ecological resilience compared to non‐spatial (conventional) management using a dynamic model of a simplified fish community with structured predation and competition that causes alternative stable states. Relative to non‐spatial management, reserves increase the resilience of the desired (predator‐dominated) equilibrium state in both stochastic and deterministic environments, especially under intensive fishing. As a result, spatial management also increases the feasibility of restoring degraded (competitor‐dominated) systems, particularly if combined with culling of competitors or stock enhancement of adult predators.     

Validation and efficacy of transgenerational mass marking of otoliths in viviparous fish larvae

Transgenerational mass marking of viviparous fish larvae in vivo was validated by intra‐muscular injection of elemental strontium chloride (SrCl₂) in gestating females and detection of the Sr in the otoliths of developing larvae. All otoliths of brown rockfish Sebastes auriculatus larvae produced from SrCl₂‐injected females showed enriched Sr:Ca ratios near the otolith edges, and the signatures did not appear to be affected by the anterior, centre and posterior positions of larvae within the ovary. Results from the present study indicate that transgenerational marking is a highly reliable technique for marking large numbers of extremely small viviparous fish larvae.     

Temporal variation and feeding ecology of juvenile Sebastes in rocky intertidal tidepools of northern California, with emphasis on Sebastes melanops Girard

This study examined the seasonal use of rocky intertidal areas by young-of-the-year (YOY) Sebastes spp. at three locations in northern California, 2003 to 2005. Six species of Sebastes were noted during the study with black rockfish Sebastes melanops comprising >99% of the total number sampled. Sebastes melanops were noted in rocky intertidal areas from May to August with peak abundances occurring in May or June. Variation in recruitment and feeding was evident among years. Diet analysis, using the index of relative importance (% I _RI) and the modified index (% I _M), showed that YOY S. melanops and Sebastes mystinus consumed a variety of prey items with harpacticoid copepods and gammaridean amphipods being the dominant prey categories. The rocky intertidal appears to serve as an important habitat for YOY S. melanops in northern California.     

Estimation of genotyping error rate from repeat genotyping,unintentional recaptures and known parent–offspring comparisons in 16 microsatellite loci for brown rockfish (Sebastes auriculatus)

Genotyping errors are present in almost all genetic data and can affect biological conclusions of a study, particularly for studies based on individual identification and parentage. Many statistical approaches can incorporate genotyping errors, but usually need accurate estimates of error rates. Here, we used a new microsatellite data set developed for brown rockfish (Sebastes auriculatus) to estimate genotyping error using three approaches: (i) repeat genotyping 5% of samples, (ii) comparing unintentionally recaptured individuals and (iii) Mendelian inheritance error checking for known parent–offspring pairs. In each data set, we quantified genotyping error rate per allele due to allele drop‐out and false alleles. Genotyping error rate per locus revealed an average overall genotyping error rate by direct count of 0.3%, 1.5% and 1.7% (0.002, 0.007 and 0.008 per allele error rate) from replicate genotypes, known parent–offspring pairs and unintentionally recaptured individuals, respectively. By direct‐count error estimates, the recapture and known parent–offspring data sets revealed an error rate four times greater than estimated using repeat genotypes. There was no evidence of correlation between error rates and locus variability for all three data sets, and errors appeared to occur randomly over loci in the repeat genotypes, but not in recaptures and parent–offspring comparisons. Furthermore, there was no correlation in locus‐specific error rates between any two of the three data sets. Our data suggest that repeat genotyping may underestimate true error rates and may not estimate locus‐specific error rates accurately. We therefore suggest using methods for error estimation that correspond to the overall aim of the study (e.g. known parent–offspring comparisons in parentage studies).     

Behaviour, growth and survival of redfish larvae in relation to prey availability

Growth, survival and condition of redfish larvae Sebastes spp., reared in the laboratory (0, 500 1500 and 4500 prey l^-1) were highest in the 1500 prey l^-1 treatment. Significantly lower larval growth and survival in the 4500 prey l^-1 treatment corresponded with lower prey bite: orient ratios in later weeks, suggesting that larvae were unable to forage efficiently at high prey densities. While these prey densities are higher than those reported in the field, naturally co-occurring Atlantic cod Gadus morhua larvae require higher prey densities when reared under similar conditions in the laboratory. These data suggest that prey availability may not be as limiting to redfish as for other commercially important marine species.     

高致病性美人鱼发光杆菌美人鱼亚种胞外产物的毒力特性分析

【目的】美人鱼发光杆菌美人鱼亚种(Photobacterium damselae subsp. damselae,PDD)是一种可导致多种海洋生物患病的重要病原菌。本研究以从我国海水养殖环境中分离的具有强磷脂酶活性、强溶血性表型且具有高致病性的2株PDD菌株为研究对象,分析PDD菌株胞外产物(extracellularproducts,ECP)的致病性及细胞毒性,及其与菌株致病性表型的相关性。【方法】利用培养基平板法测定菌株PDD1605、PDD1608的ECP体外磷脂酶活性和溶血性;通过人工感染实验测定PDD1605和PDD1608活菌株及其ECP对许氏平鲉的致病性,并进行组织病理切片观察组织的病理损伤;通过向人胚肾细胞系HEK293T和小鼠成纤维细胞系MCFS等2种培养细胞中添加菌株PDD1605和PDD1608的ECP测定其对哺乳动物的细胞毒性。【结果】人工感染PDD1605和PDD1608活菌株对许氏平鲉均表现为高致病性,5×108CFU/mL的菌液浓度24h内受试鱼全部死亡;菌株PDD1605和PDD1608的ECP对许氏平鲉同样表现为高致病性,受试鱼的死亡曲线与感染活菌株的...