Discrimination and abundance estimation of wild and released abalone Haliotis diversicolor using stable carbon and oxygen isotope analysis in north-eastern Taiwan

The discrimination between wild and released Taiwan abalone Haliotis diversicolor was performed by stable carbon isotope analysis. Abalone samples were collected from Mao Aw Gulf in north-eastern Taiwan. Live abalone and dead shells were collected by divers with an 80 × 80 cm frame. The densities and amounts of wild and released abalone, as well as the survival rates of released abalone, in 1997 and 1998 were estimated. The age of the specimens was also determined from the specific temperature of each month and the inverse relationship between oxygen isotope values and temperatures. Results show that examining stable isotopic profiles proves to be a practical and feasible method for stock discrimination as well as density and abundance estimation. These data would be helpful in assessing the success of abalone culture and release programs, which aim to enhance this valuable marine resource.     

Evaluation of shrimp polyculture system in Thailand based on stable carbon and nitrogen isotope ratios

ABSTRACT: To quantify the contribution by cocultured animals to waste assimilation in an intensive shrimp farm in Thailand, the food web structures of the macrobenthos in a reservoir pond, a shrimp culture pond and water treatment ponds were examined using the stable C and N isotope ratio technique. Seawater for aquaculture was drawn from a creek, and stored in a reservoir pond, used for farming the banana prawn Fenneropenaeus merguiensis in culture ponds, and then recycled through treatment ponds where the green mussel Perna viridis was cultured to remove organic wastes discharged from the farming. The clam worm Nereididae sp. and the mud creeper Cerithideopsilla cingulata in the culture pond had δ ¹³C values of −21.0‰ and −18.4‰, respectively, suggesting that shrimp feed (mean δ ¹³C = −20.7‰) was the main food source for these species. The δ ¹³C analysis also suggested that sediments (−23.7‰) in the reservoir pond and particulate organic matter (POM) (−24.0‰) and/or sediments (−25.0‰) in the treatment pond supplied carbon for most macrobenthic animals. However, green mussels in the treatment pond had a mean δ ¹³C value of −20.5‰, suggesting that shrimp feed was the main food source for this species.     

Differences in stability effects on the marine survival of hatchery pink salmon (Oncorhynchus gorbuscha) within the upwelling and downwelling domains of the northeast Pacific Ocean

Regional coastal conditions have a strong influence on juvenile salmon survival during their critical first months in the marine environment. Salmon (genus Oncorhynchus) survival has been thought to be favored within the high latitude downwelling domain if water column stabilities increase, whereas stability may have the opposite effect in upwelling‐dominated lower latitudes. In this study, the relationships between water column stabilities during early marine residence of pink salmon (Oncorhynchus gorbuscha) in both the upwelling and downwelling domains of the northeast Pacific Ocean and marine survival rates for hatchery stocks ranging from Vancouver Island, British Columbia, to Kodiak Island, Alaska, were explored. Contrary to expectation, there was no clear difference in the effect of stability on marine survival rates in the downwelling and upwelling domains. In both domains, marine survival rates increased for pink salmon stocks that experienced below‐average stability on the inner shelf during early marine residence. Stability effects from the outer shelf showed no consistent relationship to marine survival within the northeast Pacific.     

Differences in stable isotope ratios of Dall’s porpoises (Phocoenoides dalli) between coastal and oceanic areas of the North Pacific

Carbon and nitrogen stable isotope ratios in the muscle of Dall’s porpoises were measured. Samples were collected from the catches of the hand harpoon fishery, incidental catches of drift net, and scientific research on the use of drift nets. Samples were from the North Pacific, Sea of Japan, Sea of Okhotsk, and Bering Sea. Although no variation in δ¹⁵N was observed, δ¹³C was significantly different between population groups near Japan and the oceanic North Pacific and Bering Sea. The difference may be due not only to local variation in prey species, but also to an overall difference in carbon stable isotope ratios that originate from coastal benthic or oceanic pelagic‐based food webs. We differentiated Dall’s porpoise population groups from both areas using carbon stable isotope ratios with an error rate of <5%. Although further study is needed, our results suggest that carbon stable isotope ratios could possibly be an indicator of whether a Dall’s porpoise belongs to a coastal benthic or oceanic pelagic food web.     

Depletion of naturally recruited wild Japanese eels in Okayama,Japan, revealed by otolith stable isotope ratios and abundance indices

To investigate the population dynamics of naturally recruited wild Japanese eels, fisheries data of wild individuals in Okayama Prefecture were investigated as a case study. Wild and stocked eels were discriminated using a recently developed method based on otolith stable isotopes. Of the 161 eels captured in freshwater areas where eels had been stocked, 98.1% were discriminated as stocked. In contrast, 82.8% of 128 eels captured in coastal areas where eels are not stocked were discriminated as wild. There was a significant decrease in longline and set-net catch per unit effort between 2003 and 2016 in the coastal areas where most eels were discriminated as wild, indicating ongoing depletion of wild Japanese eels in these waters.     

Fecundity, egg size and early hatchery survival for wild Atlantic salmon, from the River Bush

Abstract  A total of 118 wild Atlantic salmon, Salmo salar L., females were stripped at the River Bush Salmon Station. The total number of eggs (fecundity) and egg diameters were compared for three age groups of adults. Adult length explained the majority of the variation in fecundity whilst freshwater age explained the majority of the variation in egg diameter. Parallel regression analysis for the total number of eggs on fish length relation for 3 years (2000–2002) showed significant temporal variation among years. Larger eggs from 2.1+ adults produced longer and heavier swim-up fry than smaller eggs from 1.1+ adults. There was also the suggestion that the survival of eggs from 1.1+ adults was lower than eggs from 2.1+ adults to the swim-up stage.     

Genetic heterozygosity and meristic character variance in a wild Atlantic salmon population and a hatchery strain derived from it

Heterozygosity at seven enzyme loci was compared with the degree of fluctuating asymmetry of three bilateral traits in a wild population of Atlantic salmon (Salmo salar L.) and a hatchery strain derived from it. In the wild population, average heterozygosity per fish was higher (p < 0.01) and average asymmetric value per fish was lower (p < 0.01), compared with the hatchery strain. Analyses at the intrapopulation level did not provide unequivocal support for the relationship between heterozygosity and developmental stability, with correlation between the number of heterozygous loci per fish and the asymmetric value per fish being non-significant. However, comparisons of asymmetric value per fish between homozygous and heterozygous individuals at separate loci indicated that heterozygotes had significantly lower asymmetry values per fish at IDDH-1* in the hatchery sample. These results are discussed in relation to the potential utility of fluctuating character asymmetry as an indicator of loss of heterozygosity in cultured Atlantic salmon stains.     

Variability in performance in wild Atlantic salmon, Salmo salar L., fry from a single redd

Dispersal and growth were studied in Atlantic salmon, Salmo salar L., fry from a natural isolated redd. The distribution of fry leaving the redd was strongly peaked, 80% being caught within a 2-week period. Early in the dispersal period, all fry leaving the redd had remnants of yolk sac and had not fed; by half way through the dispersal period, no fry had any visible yolk, but 35% still had empty stomachs. Fry leaving the redd during the first half of the dispersal period tended to settle in different first feeding sites than those dispersing later. Predation on fry by larger salmonids was frequent, especially during dispersal. Coefficients of variation for length, weight and condition factor increased significantly over the study period and for individually recognised fry, growth rates varied markedly. Thus, individual salmon fry differ in physical status on emergence from the redd and these differences are amplified during the first few weeks after emergence.     

Changes in rhodopsin-porphyropsin ratio of chum and pink salmon

ABSTRACT:   In order to investigate the changes in rhodopsin-porphyropsin ratio of chum salmon and pink salmon in relation to the change in their habitat, the ratios were analyzed in individual fish prior to stocking, during the sea run, homing, and upstream migration. The ratio in both the species gradually increased during the sea run. However, the ratio decreased after upstream river migration. Moreover, in the sea, the rhodopsin-porphyropsin ratio of chum salmon was always slightly higher than that of pink salmon. The largest difference in the individual variation was observed in the individuals caught with a set net placed near the mouth of a home river.     

Differences in sea migration between wild and reared Atlantic salmon (Salmo salar L.) in the Baltic Sea

The effect of origin, smolt size and year of release on the sea migration pattern of Atlantic salmon (Salmo salar L.) in the Baltic Sea was examined by tagging experiments conducted in 1991–1993 on wild and reared smolts of the Simojoki river salmon stock. The tag recovery data analysed by log-linear models revealed significant differences in both spatial and temporal sea migrations between the wild and reared salmon; the variation was attributed to the year of release and to the origin of the fish. Grilse accounted for the majority of reared returners (76%) but for a smaller proportion (46%) of the wild fish. The effect of smolt size could be studied only in the smolt groups tagged in 1991. Wild fish were more frequently (71%) caught in the Baltic Main Basin than were reared fish (51%) during their second sea year, and the size variation between wild and reared smolts did not explain the recovery site. No such differences in spatial distribution were found during the third sea year. The tagging place (hatchery/trap) of the reared fish did not affect their later sea migration. The differences in sea migration patterns suggest that the wild salmon are more vulnerable to the intensive salmon fishery in the Baltic Main Basin than are reared fish.     

Competition between Asian pink salmon (Oncorhynchus gorbuscha) and Alaskan sockeye salmon (O. nerka) in the North Pacific Ocean

The importance of interspecific competition as a mechanism regulating population abundance in offshore marine communities is largely unknown. We evaluated offshore competition between Asian pink salmon and Bristol Bay (Alaska) sockeye salmon, which intermingle in the North Pacific Ocean and Bering Sea, using the unique biennial abundance cycle of Asian pink salmon from 1955 to 2000. Sockeye salmon growth during the second and third growing seasons at sea, as determined by scale measurements, declined significantly in odd‐numbered years, corresponding to years when Asian pink salmon are most abundant. Bristol Bay sockeye salmon do not interact with Asian pink salmon during their first summer and fall seasons and no difference in first year scale growth was detected. The interaction with odd‐year pink salmon led to significantly smaller size at age of adult sockeye salmon, especially among younger female salmon. Examination of sockeye salmon smolt to adult survival rates during 1977–97 indicated that smolts entering the ocean during even‐numbered years and interacting with abundant odd‐year pink salmon during the following year experienced 26% (age‐2 smolt) to 45% (age‐1 smolt) lower survival compared with smolts migrating during odd‐numbered years. Adult sockeye salmon returning to Bristol Bay from even‐year smolt migrations were 22% less abundant (reduced by 5.9 million fish per year) compared with returns from odd‐year migrations. The greatest reduction in adult returns occurred among adults spending 2 compared with 3 years at sea. Our new evidence for interspecific competition highlights the need for multispecies, international management of salmon production, including salmon released from hatcheries into the ocean.     

象山缢蛏养殖群体和野生群体遗传多样性的比较

于2001年4月，在浙江象山港虾塘和象山外海滩涂分别采集100个缢蛏(Sinonovacula constricta Lamarck)样品，采用聚丙烯酰胺凝胶电泳技术，分析了2个群体各38个样本的EST、ADH、MDH、IDH、ME、LDH、GDH、SOD、SDH、ATP等10种同工酶，分别记录了30、29个基因位点。其中s-MDH-1、SDH、s—ME、ATP-1、ATP-2等5个位点为多态位点。象山野生缢蛏群体的多态位点比例(17．24％)和群体平均杂合度观察值(0．0377)都明显高于养殖群体(16．67％，0．0314)。结果表明，与其他贝类比较缢蛏象山养殖和象山野生群体拥有较低的遗传变异水平，其中象山野生群体比养殖群体遗传变异水平高。     

Predation on wild and hatchery salmon by non‐native brown trout (Salmo trutta) in the Trinity River,California

Non‐native predators may interfere with conservation efforts for native species. For example, fisheries managers have recently become concerned that non‐native brown trout may impede efforts to restore native salmon and trout in California's Trinity River. However, the extent of brown trout predation on these species is unknown. We quantified brown trout predation on wild and hatchery‐produced salmon and trout in the Trinity River in 2015. We first estimated the total biomass of prey consumed annually by brown trout using a bioenergetics model and measurements of brown trout growth and abundance over a 64‐km study reach. Then, we used stable isotope analysis and gastric lavage to allocate total consumption to specific prey taxa. Although hatchery‐produced fish are primarily released in the spring, hatchery fish accounted for most of the annual consumption by large, piscivorous brown trout (>40 cm long). In all, the 1579 (95% CI 1,279–1,878) brown trout >20 cm long in the study reach ate 5,930 kg (95% CI 3,800–8,805 kg) of hatchery fish in 2015. Brown trout predation on hatchery fish was ca. 7% of the total biomass released from the hatchery. Brown trout only ate 924 kg (95% CI 60–3,526 kg) of wild fish in 2015, but this was potentially a large proportion of wild salmon production because wild fish were relatively small. As large brown trout rely heavily on hatchery‐produced fish, modifying hatchery practices to minimise predation may enhance survival of hatchery fish and potentially reduce the abundance of predatory brown trout.     

Multi‐timescale interactions between pink and chum salmon catch per unit effort in the Bering Sea

Based on generalized linear models, interspecific interactions were identified between chum and pink salmon. In addition, the effects of sea surface temperature and location on the variability of catch per unit effort (CPUE) of chum salmon from gill‐net surveys carried out between 1972 and 2010 were investigated. In the optimal model, interspecific interactions between CPUEs of chum and pink salmon on a year scale were positive for approximately half of all years in the central Bering Sea. In addition, interspecific interactions on a multi‐year scale were positive in even‐numbered years. The effects of location on the CPUE of chum salmon were significant variables in the optimal model. The CPUEs of chum salmon located near the continental shelf in the Bering Sea were higher than those of other locations. This study provides new evidence of positive interspecific interactions between the CPUEs of chum and pink salmon. The results also suggest that the standardized CPUE of chum salmon from the gill‐net surveys reflects relative chum salmon abundance in the North Pacific Ocean in the following year.     

中华绒螯蟹幼蟹碳稳定同位素周转速率与碳、氮分馏系数的测定

为测定生长与新陈代谢对不同规格中华绒螯蟹幼蟹和不同组织碳稳定同位素周转速率的影响及分馏系数,本在水族箱（0.2 × 0.2 × 0.3 m）中分别养殖EA组（4.0 g ± 0.5 g）和EB组（15.5 g ± 0.5 g）2组中华绒螯蟹幼蟹,分别于0、7、14、21和28 d时采集幼蟹的肝胰腺、肌肉和鳃组织,探究其碳稳定同位素周转过程,并测定了幼蟹对食物碳、氮稳定同位素的分馏系数。结果显示,EA组幼蟹碳稳定同位素的周转速率大于EB组,周转速率随着幼蟹规格的增大而减小。幼蟹肝胰腺的周转速率最快,其次是肌肉,最后是鳃,其中EA组幼蟹肝胰腺、肌肉和鳃的半衰期分别为20.88、29.37和34.14 d,EB组分别为21.73、35.18和66.01 d。新陈代谢是驱动幼蟹体内碳稳定同位素周转的主要因子,幼蟹肝胰腺、鳃和肌肉中新陈代谢占碳稳定同位素周转的贡献百分比分别为79.82% ~ 94.04%、（67.00% ~ 81.90%和71.61% ~ 90.36%。幼蟹对饵料碳、氮稳定同位素的分馏系数分别为0.98‰ ± 0.19‰和3.01‰ ± 0.02‰。本研究不仅对中华绒螯蟹幼蟹的营养生态学研究提供参考,还为中华绒螯蟹养殖过程中的饵料选择提供了科学依据。     

Discrimination of nursery locations of juvenile Japanese flounder Paralichthys olivaceus on the Pacific coast of northern Japan based on carbon and nitrogen stable isotope ratios

Fisheries Science - To test whether stable isotope ratios of carbon (δ13C) and nitrogen (δ15N) can be used to understand the ecological connectivity of Japanese flounder Paralichthys...     

香鱼野生群体和养殖群体遗传多样性比较

香鱼是分布于中国、日本和朝鲜的一种珍稀名贵经济鱼类,本实验比较分析了香鱼养殖和野生群体的遗传多样性。研究结果显示,在长度为445 bp的控制区部分序列上,鳌山卫养殖群体的单倍型多样度h(0.198 4±0.092 4)和核苷酸多样度π(0.000 8±0.000 9)显著低于东张水库野生群体(h=0.810 5±0.067;π=0.002 6±0.002 0),两群体产生了较大的遗传分化(F st=0.447,P=0);单倍型邻接关系树的拓扑结构简单,未呈现明显的地理谱系结构,日本香鱼个体与中国香鱼亲缘关系较远;东张群体的历史动态分析结果表明其可能经历过近期的群体扩张事件。无论是养殖群体还是野生群体,中国香鱼群体的遗传多样性现状不容乐观。