Changing salmon: An analysis of body mass,abundance, survival,and productivity trends across 45 years in Puget Sound

Pacific salmon and trout (Oncorhynchus spp., Salmonidae) of the Puget Sound region of Washington State, USA, have experienced recent and longer‐term (multidecadal) variability in abundance while supporting robust fisheries. As part of the post‐season salmon management process, population‐specific estimates of total adult abundance to Puget Sound (Strait of Juan de Fuca) for pink (O. gorbuscha), chum (O. keta), coho (O. kisutch), sockeye (O. nerka), and Chinook (O. tshawytscha) salmon and steelhead trout (O. mykiss) are calculated annually. We compiled annual estimates of body mass, abundance and survival of hatchery‐ and naturally produced salmon from 1970 to 2015 to compare spatial and temporal patterns across species. Average weights of adult salmon and steelhead returning to Puget Sound, with the exception of coho salmon, have decreased since the 1970s. Temporal trends in abundance, survival and productivity varied by species and origin (hatchery vs. naturally produced). Generally, abundance and survival rates of natural‐origin species decreased whereas those of hatchery‐produced species did not, which is in contrast with other studies' general conclusions of decreasing survival among Puget Sound salmonids. Species diversity has decreased in recent years, with salmonids that rely on a short freshwater rearing phase in the natural environment (hatchery‐produced fish and naturally produced pink and chum) representing >90% of total returns in most years. This new information reveals patterns of body size, abundance, survival and productivity across species, life history and rearing type over the past 45 years and, in doing so, demonstrates the strength in multidecadal, multifactor time series to critically evaluate salmonid species.     

Serum chemistry of diseased English sole, Parophrys vetulus Girard, from polluted areas of Puget Sound, Washington

Relationships between selected serum components and microscopically detected idiopathic liver and kidney lesions were evaluated for English sole, Parophrys vetulus, sampled from urban and non-urban areas of Puget Sound, Washington. The normal range for each serum chemistry parameter was based on English sole with no lesions, or sole with minor parasitic conditions or with lesions in tissues other than liver and kidney which did not significantly affect serum chemistry values. Generally, sole with idiopathic liver lesions had significantly different haematocrit values and levels of serum albumin, calcium, and bilirubin when compared to sole which were free of idiopathic liver and/or kidney lesions. Serum aspartate aminotransferase and alanine aminotransferase activity and serum levels of glucose, total protein, phosphates and magnesium were also abnormal, but appeared to be associated only with certain types of liver lesions. No association between kidney lesions and abnormal serum chemistry values was identified. In addition, English sole sampled from some urban areas of Puget Sound had particular serum chemistry values and liver lesion prevalences which were significantly different from those of sole sampled from non-urban areas. These findings support the hypothesis that sole near highly urbanized environments may display other signs of impaired health in addition to high prevalences of tissue lesions. Thus, measurements of serum chemistry parameters, in conjunction with histopathological examination, appear to be useful techniques for evaluating the health of English sole.     

人工鱼礁结构设计原理与研究进展

为了解侧板结构对八棱柱型人工鱼礁流场效应的影响,实验基于计算流体力学方法 (computational fluid dynamics, CFD),利用大涡模拟 (LES)对4种不同侧板结构的八棱柱型人工鱼礁周围流场变化进行数值模拟,并以上升流体积、背涡流体积和向上输运通量等为流场效应指标进行了分析,同时利用水槽实验对数值模型进行验证。结果显示,水槽实验流速与2种尺寸数值模拟流速的均方根误差最大不超过0.065。0°垂直迎流时,2种来流速度下,A型、C型和D型礁的上升流体积较B型礁最大分别高35.6%、244.1%和80.1%,背涡流体积较B型礁最大分别高193.5%、115.8%和88.8%。C型和D型礁的向上输运通量均大于A型礁,且C型礁最大向上输运通量是D型礁的1.29倍。不同迎流角度下,C型礁和D型礁的上升流体积和背涡流体积在4种角度下差异显著,且迎流面投影面积和上升流体积及背涡流体积之间相关系数较小。研究表明,实验所采用的数值模拟准确可靠;侧板数量增加对于提升八棱柱型人工鱼礁流场效应尤其是上升流效应作用明显;下层侧板固定时,上层为倾斜侧板有利于提升礁体的上升流效应,上层为垂直侧板时有利于提升礁体的背涡流效应;不同的侧板组合会影响礁体对迎流角度的适应性。本研究结果可为鱼礁单体的优化设计以及大尺度海洋数值模型中阻力参数设定提供参考。

     

Chinese integrated fish farming: a comparative bioeconomic analysis

This paper provides an overview of the structure and performance of Chinese integrated pond fish farming systems, based on analysis of survey data for 1013 ponds on 101 farms in eight Chinese provinces. A province-by-province examination of gross and net fish yields supports the traditional Chinese classification of provinces into high, medium and low productivity classes according to fish farm output: average net fish yields for surveyed ponds in each class were 7958,4981 and 3321 kg ha^?1 year^?1 respectively. The paper includes summaries and analyses of data on fish stocking and harvesting, use of feeds and fertilizers, fish-animal integration, capital inputs, and the overall cost and revenue structure in each productivity class. In addition to variations in aggregate input and output levels, a key difference between productivity classes is seen to lie in the stocking model utilized: filter-feeding fish dominate in poorer areas, while ‘feeding fish’ (grass carp, Ctenopharyngodon idella (Valenciennes), black carp, Mylopharyngodon piceus (Richardson), and omnivorous carps) dominate in high-productivity provinces. These results are examined in light of regional differences in culturing tradition, socio-economics, infrastructure, climate and geographical factors.     

A Preliminary Study of the Spatial Variation in Growth of Raft-Cultured Blue Mussels Mytilus trossulus in Northern Puget Sound, Washington

Abstract.– The effects of culture rope density (high and low), position (inside, middle. and outside), and depth (1, 3, and 5 m) on growth rates, expressed as mean shell length increase (mm) per day, were quantified in raft-cultured blue mussels Mytilus trossulus in northern Puget Sound during the fall of 1993. Growth rates differed by as much as 20% after the 90-d experimental period, and varied significantly according to culture rope position, but not according to culture rope density or depth. Furthermore, a three-way analysis of variance revealed a significant first-order interaction effect, culture rope density × depth. The significant culture rope position effect was due to the higher growth rate (mean ± SEM) of mussels on outside culture ropes (0.199 ± 0.009 mm/d) compared to inside culture ropes (0.168 ± 0.007 mm/d). The interaction effect was due to the significantly higher growth rates of mussels at I and 3 m (0.197 ± 0.009 and 0.204 ± 0.011 mm/d, respectively) compared to 5 m (0.162 ± 0.014 mm/d) under low culture rope density conditions, and the significantly higher growth rate of mussels at 3 m under low culture rope density conditions (0.204 ± 0.011 mm/d) compared to high culture rope density conditions (0.168 ± 0.012 mm/d). Practical raft management is affected by such variation in growth. Commercial mussel growers may find it necessary to alter their culture methods to insure a more uniform product from seed to harvest.     

Transaction costs in contract farming models for mussel and oyster farming in South Africa: Organisational and management implications

Abstract

This study examines transaction costs faced by small mussel and oyster growers to elicit the appropriate organisational design of contract institutions. The theoretical premise is that high transaction costs essentially constrain the participation of small growers in mussel and oyster mariculture. Transaction cost analysis is applied to contract farming models and this approach is first discussed conceptually. Experience with contract farming by small growers in a developing context is synthesised and used in guiding the design of contract farming models. This is followed by a brief overview of the mussel and oyster industries, which is used to gain insight into transaction costs associated with contract institutions. Contracting models and implications are assessed separately for each industry. For mussel mariculture, four farming models are examined and the appropriate model is subsequently selected. For oyster mariculture, the transaction costs of contract fanning are examined to assist in organisational design.     

Factors influencing densities of non‐indigenous species in the ballast water of ships arriving at ports in Puget Sound,Washington, United States

• 1. Oceanographic characteristics and the presence of international shipping in Puget Sound, Washington, USA contribute to its vulnerability to non‐indigenous species (NIS) invasions. To evaluate NIS arriving in ballast water, zooplankton was sampled in 380 ballast tanks of ships after they entered Puget Sound.
• 2. Taxa were classified into a higher risk group of coastal organisms (including known NIS), and a lower risk group of largely oceanic species. Most ships reported conducting mid‐ocean ballast water exchange (BWE). However, despite state regulations requiring BWE, and apparent compliance by ship operators, most sampled tanks from both transpacific and coastal routes had coastal zooplankton densities exceeding internationally proposed discharge standards.
• 3. BWE efficiency models and controlled before‐and‐after BWE experiments indicate that BWE consistently removes most coastal zooplankton. However, this study found that although the empty–refill method of BWE significantly reduced coastal plankton compared with un‐exchanged tanks, the flow‐through method did not, and in either case remaining coastal plankton densities presented appreciable risks of introducing NIS.
• 4. Densities of high risk taxa were consistently and significantly higher from US domestic trips dominated by tank ships carrying ballast water from California, and lower in samples from trans‐Pacific trips dominated by container ships and bulk carriers with ballast from Asia. These findings are probably a result of the dense and diverse NIS assemblages present in California and other US west coast estuaries and the comparatively short transit times between them and Puget Sound.
• 5. While it appears that BWE can effectively replace NIS with less risky ocean species, new reporting, verification, and operational procedures may be necessary to enhance BWE efficacy. In the long‐term, the introduction of ballast water treatment technologies may be required to significantly reduce the discharge of risky organisms from commercial ships if BWE practices do not become more effective.

Copyright © 2008 John Wiley & Sons, Ltd.     

Economic feasibility of prawn Macrobrachium production in South Carolina,USA

Cost and returns were estimated for freshwater prawn Macrobrachium rosenbergii farming as a supplemental enterprise in South Carolina in relation to the following factors: (1) existing versus new investment for ponds and water supply; (2) three stocking strategies (postlarvae alone, a 50:50 mixture of postlarvae and nursed juveniles and nursed juveniles alone) at various densities (2·15–8·61 prawns m^?2); (3) a range of prices for seed stock ($0–50 per thousand); and (4) two marketing alternatives (sale of product as shrimp tails only or with the large animals marketed heads-on and the rest as tails). Net revenue estimates indicate that prawn aquaculture has potential to become a source of supplemental income to farmers in the coastal plain area of South Carolina and throughout much of the southeastern United States. This is especially likely if the enterprise can utilize existing pond facilities that are already discounted into the value of the land or were constructed during a period of lower investment costs. A prawn farm is unlikely to be profitable if postlarvae alone are stocked, even in existing facilities, but if a mixture of postlarvae and juveniles or juveniles alone are stocked in existing facilities, profitability is likely at seed costs up to about $40 per thousand.     

Three dimensional numerical modeling using a multi-level nesting system for identifying a Water layer suitable for scallop farming in Tongyeong,Korea

Three-dimensional modeling was performed in Tongyeong, South Korea to identify a space suitable for Yesso scallop farming that may not be successful if seawater temperature remains above 22 °C. In the research area, an underwater basin was found at a depth of 70 m; the depth outside the basin was not deeper than 30 m. It was expected that the water temperature in the interior of the basin might be low enough for farming during summer. The present study was then designed to investigate the temperature distribution in this basin area to verify if a water layer with consistently low temperature existed below the surface layer, using a MOHID (MOdelo HIDrodinámico) three-dimensional numerical model. The model applied mixed vertical coordinates so that the difficulties in modeling near the basin, where water depth sharply changes, could be overcome. In addition, a multi-level nesting system was developed based on the 72 -h forecasting system of the sea status around South Korea, which increased the modeling accuracy using updated boundary conditions. The model was validated by the measured tide and temperature data. The results showed that a strong thermocline was formed at depth of 15 m and a sub-surface space existed at depths deeper than 30 m, where seawater temperature was lower than 22 °C even in summer, which indicates the possibility of successful farming in the research area. The measurements also supported this result because dissolved oxygen and chlorophyll-a were not scarce in the sub-surface space probably due to the strong tidal mixing that could bring the surface seawater properties down below the thermocline. It was also found that the model was effective in resolving the thin thermocline and the sub-surface space below it due to the mixed vertical coordinate system.     

Status of freshwater prawn farming: a review

Farmed freshwater prawn production globally expanded by a factor of 3.5 in the 7 years from 1984 to 1991 but declined by 17% to 31 235 tin 1992. This was caused by a 53% reduction in the output of Taiwan due to disease and in-breeding problems, partially compensated by increases elsewhere, notably in India and Vietnam. This paper reviews the scientific literature published between 1989 and 1994 on the culture of the freshwater prawn Macrobrachium rosenbergii (De Man 1879) and summarizes earlier work. Broodstock and larval studies, nutrition, grow-out management, genetics, integrated aquaculture and disease and water quality are covered. Finally, a brief summary of the status and characteristics of prawn culture in the major farming locations is presented, together with some comments on the opportunities and constraints for further development.     

关于南美白对虾的养殖技术之一南美白对虾淡水养殖技术分析

近两年,南美白对虾低盐度淡水养殖在我国南方沿海省份发展迅速,因养殖场地所处的江沿岸、盐碱荒滩邻近海岸线,直接或间接地利用了海水潮汐作用,盐度大都在2‰以上,所以这些淡水养殖均应属低盐度水养殖.若将南美白对虾引入内陆省份江河湖泊的纯淡水中养殖,其发展前景、市场潜力、社会、经济效益将无法估量.南美白对虾纯淡水养殖的成败,取决于采取的养殖技术是否可行.即:1、生产的淡化苗种能否适宜在淡水中生长.2、淡水人工调兑技术方案是否可行.3、淡水养殖效益如何.     

Technical inefficiency of Vietnamese pangasius farming: A data envelopment analysis

Vietnamese pangasius farming needs to produce efficiently to compete in world markets. This study investigates the input- and output-specific technical inefficiency of Vietnamese pangasius farmers. First, we used a Russell-type (input–output) directional distance function to estimate the input- and output-specific technical inefficiency. Second, we applied a bootstrap truncated regression to analyze the factors influencing these technical inefficiencies. Results show that the main challenges for enhancing the performance of Vietnamese pangasius production are inadequate use of capital assets (inefficiency of 42%) and improper methods to achieve higher fish yield (inefficiency of 30%). Input-specific technical inefficiency (pond area and feed) is negatively associated with the experience and education level of pangasius farmers. Location of the farm in a saltwater intrusion area is positively associated with the inefficiency of producing fish. Outcomes of this study are useful to identify successful strategies to minimize the use of inputs while simultaneously maximizing fish production.     

Bio-economic analysis of super-intensive closed shrimp farming and improvement of management plans: a case study in Japan

Fisheries Science - Crustacean aquaculture is a multibillion-dollar industry worldwide that continues to show significant growth. Shrimp farming has been intensified for decades, and...     

Studies on triploid oysters in Australia: farming potential of all-triploid Pacific oysters, Crassostrea gigas (Thunberg), in Port Stephens, New South Wales, Australia

Triploid Pacific oysters Crassostrea gigas farmed in Port Stephens, NSW had an exceptionally fast growth rate and reached a whole weight of 55 g in 13 months versus 20 months for diploids. Mortality of the triploids (24.5±2.94%) was significantly lower (P<0.05) than that of the diploids (40.0±2.26%) over the duration of the experiment (July 2002–February 2004). Unfortunately, this advantage was offset by discoloration of the meats of the triploids when they were in better condition than the diploids over summer (October 2003–March 2004). However, discoloration of meat of triploids had cleared up by April 2004 and neither did they suffer this problem from April–September 2003. The triploids also had a lower peak condition than the diploids. Oysters in peak meat condition, i.e. spawning condition, are preferred for the half shell trade in Australia and in this study, there was at least a six‐month period prior to discoloration, when the triploids were large enough and had sufficient meat condition for marketing on the half shell.     

Fertilization success of the New Zealand geoduck,Panopea zelandica: Effects of sperm concentration,gamete age and contact time

Valuable aquaculture and fisheries industries for the North American geoduck, Panopea generosa, have driven interest in developing similar ventures for other geoduck species including P. zelandica from New Zealand. However, little is known about the fertilization kinetics of this species, or the conditions under which the amount and quality of larvae can be maximized. We determined the effects of sperm concentration, gamete age and contact time on the fertilization success of P. zelandica using an extended‐Vogel‐Czihak‐Chang‐Wolf (EVCCW) model. The model provided a good fit to laboratory data when applied to individual contact times. For a contact time of 10 s, optimal fertilization was achieved at concentrations of approximately 10⁴ sperm μL^?1, but this decreased to as little as 10² sperm μL^?1 for contact times of several minutes. Optimal fertilization was always <100% (max. observed 70%) and the proportion of fertilized eggs decreased rapidly at sperm concentrations above the optimal. According to the model this was due to a slow block to polyspermy. If commercial hatchery facilities ensure that broodstock are in ripe condition, and use sperm <30‐min old, then optimal fertilization can be expected at sperm densities of 10²–10³ sperm μL^?1 at contact times of 5–10 min.     

Correction to: Bio-economic analysis of super-intensive closed shrimp farming and improvement of management plans: a case study in Japan

Fisheries Science - The article "Bio-economic analysis of super-intensive closed shrimp farming and improvement of management plans: a case study in Japan", written by Junpei Shinji,...     

Key factors influencing transport of white shrimp (Litopenaeus setiferus) post-larvae into the Ossabaw Sound system, Georgia, USA

We examined conditions under which white shrimp (Litopenaeus setiferus) post‐larvae enter an estuarine channel receiving high freshwater discharge and one receiving negligible discharge in the Ossabaw Sound system of Georgia, USA, during 1997 and 1998. We used surface nets to collect plankton over several 14‐day periods, during which consecutive tows were made at night against the flooding current at stations in the inlet channels. During these sampling periods, additional intensive periods of around‐the‐clock surface and near‐bottom (using a bottom sled) plankton tows were made. Data on oceanographic conditions were obtained from moored instrument arrays and shipboard sampling. We identified three key factors that influenced the densities of post‐larval white shrimp in time and space within the Ossabaw inlet system. The first factor was a critical minimum temperature of coastal waters of 27–28°C. Once the threshold temperature was reached, lunar tidal stage became a key factor when the full duration of the flood tide coincided with darkness during peak ingress. This peak also coincided with an increase in water level within the system by more than 0.2 m, which induced an additional influx of water that reinforces the flood current over the ingress period. Our results suggest that the direction of subtidal currents (into or out of the system) becomes a significant factor in post‐larval ingress when influx of water coincides with the time of favorable temperature conditions and nighttime flood tides.     

Demographics of the spawning aggregations of four catostomid species in the Savannah River, South Carolina and Georgia, USA

Abstract –  Differences in the life history strategies employed by otherwise ecologically similar species of a fish assemblage may be an important factor in the coexistence of these species and is an essential consideration in the conservation and management of these assemblages. We collected scales to determine age and growth of four species of the catostomid assemblage (northern hogsucker Hypentelium nigricans , spotted sucker Minytrema melanops , notchlip redhorse Moxostoma collapsum and robust redhorse Moxostoma robustum ) of the Savannah River, Georgia–South Carolina in spring 2004 and 2005. Robust redhorse was the largest species; reaching sexual maturity at an older age and growing faster as a juvenile than the other species. Spotted sucker did not achieve the same size as robust redhorse, but reached sexual maturity at younger ages. Notchlip redhorse was intermediate between the abovementioned two species in age at maturity and size. Northern hogsucker was the smallest species of the assemblage and reached the sexual maturity at the age of three. Both robust redhorse and spotted sucker were sexually dimorphic in size-at-age. The range of life history strategies employed by Savannah River catostomids encompasses the range of life history strategies exhibited within the family as a whole.     

Bioeconomic evaluation of Eleutheronema tetradactylum farming: a case study in Taiwan

Eleutheronema tetradactylum is a recently developed product in aquaculture systems in Taiwan. Its production is concentrated in the Pingtung and Kaohsiung counties of Taiwan during the overwinter and oversummer seasons. In this study, a bio-economic approach was applied to investigate the mechanisms and economic profitability of commercial E. tetradactylum farming. The analysis consisted of two parts: (1) a cost–benefit analysis to determine the main components affecting profitability; and (2) multivariate statistics to clarify the relationship between biological and economic factors. The findings suggest that fry quality is an important factor in increasing the survival rate in aquaculture systems, and that increased survival rate in turn generates increased farm profitability and expansion options during the oversummer season, thus providing better economic performance. As feed cost is the key factor affecting production, improving feed management could increase the profitability of E. tetradactylum farming.