Current approaches to the enhancement of fisheries

With increasing pressure on the world's inland and coastal marine fisheries, increases in production and quality of yield are being sought through the application of a range of enhancement techniques. Which of these is applied depends on the attitude to the natural resource by societies at different levels of economic development. The range of enhancement techniques involves increasing levels of human input and control which raise productivity significantly, but which also raise costs. Introductions have raised production in many areas of the world at the price of the risk of environmental disruption. Stocking is extremely widespread but has generally been applied uncritically. A variety of models are proposed to serve as a basis for more rigorous evaluation of biological and economic effectiveness of this practice. Fertilization of water bodies is used to raise levels of production further. Elimination of unwanted species then becomes necessary to maximize benefits from the target species. Adjustments to the habitats within the water body assist in raising general levels of productivity which culminate in the conversion of areas of the water into fish ponds or for cage culture. This process has important implications for the social, economic and policy context which necessitates shifts in ownership, finance and education among populations where these types of development occur.     

Impacts of stock enhancement strategies on the effective population size of Murray cod,Maccullochella peelii,a threatened Australian fish

Abstract Murray cod, Maccullochella peelii (Mitchell) is an iconic Australian species endemic to the Murray‐Darling Basin (MDB) of inland south‐eastern Australia. Murray cod has been a valuable food source and supported a large commercial fishery throughout much of the 20th century. Over‐fishing and habitat destruction have resulted in significant declines in Murray cod populations throughout much of its range. Since the early 1980s, large numbers of Murray cod have been stocked into waterways to support both recreational fishing and conservation efforts. In this study, the likely impacts of past and current stocking practices on genetic diversity of Murray cod were modelled and new strategies to maximise genetic diversity in stocked populations are explored. The results suggest that a large, well‐managed breeding and stocking programme could help maintain genetic diversity of Murray cod across the MDB. In catchments within the MDB where the effective population size is very small, a well‐designed stocking programme, following strict guidelines for numbers of families reared and number of individuals maintained per family, could increase genetic diversity in a few generations.     

Non-native fish in the fresh waters of Portugal, Azores and Madeira Islands: a growing threat to aquatic biodiversity

Abstract  Portugal, the Azores, and Madeira had a combined total of twenty six non-native fish species introductions, with the mainland having the highest number (twenty three), followed by the Azores with ten and Madeira with two records. Fifteen of these species established in Portugal, six in the Azores and one in Madeira. The oldest known introduction (1792) was goldfish, Carassius auratus (L.), while the newest (2005) was tinfoil barb, Barbonymus schwanenfeldii (Bleeker). Ten species had been introduced in Portugal by the beginning of 20th century, but the rate of introduction continues to increase, with four species introduced since 2000. In mainland Portugal, the Douro, the Tejo and the Guadiana drainages had the highest number of introduction records, while the Lima and the Mira drainages had the fewest. Management measures are offered to reduce current rate of fish introductions in Portuguese watersheds.     

Effects of fish stocking on the zooplankton community structure in a shallow lake in China

Abstract  Changes in the zooplankton community structure in relation to fishery practices in Lake Donghu, Wuhan, China were examined. The number of Protozoa species increased slightly, whereas the number of rotifers and crustaceans decreased from the 1960s to the 1990s. The total annual average densities of zooplankton increased 15–20 times in the 1990s compared with the 1960s. This increase was largely attributed to Protozoa, which contributed 93.4% by number of the total zooplankton density in 1991. Cladoceran densities decreased markedly from 1987. Changes in densities of rotifers and copepods were not evident. Trends in zooplankton biomass were similar to density. Large changes in zooplankton community structure coincided with markedly changes in concentration of chlorophyll a and transparency in Lake Donghu in 1987. The year 1987 seems to be the threshold year when the zooplankton community structure changed considerably. These changes were related to continuously increasing fish stock biomass in the lake. It was suggested that fish stocking and fish biomass should be a better managed for improvement of the quality of the lake's environment.     

象山港海洋牧场建设与生物资源的增殖养护技术

通过生物资源生境营造、适宜性增殖物种筛选与应用、牧化物种增殖与采捕、效果评估和管理等技术的研究与运用,建立有效恢复生物资源、实现天然水域渔业生物资源产出功能最大化的象山港海洋牧场示范区。至今已建成由15个圆角六边形和1 000个台面框架型诱导礁组合而成的7个鱼礁群,面积25 hm~2,形成空方规模53 810 m~3;移植海带、坛紫菜和龙须菜等大型海藻,建成以浮式平面藻床为主的人工藻场80 hm~2。底播毛蚶、栉江珧等贝类2 000万粒;年放流大黄鱼、黑鲷、黄姑鱼、褐鲳鲉等鱼类苗种160万尾;中国明对虾、日本对虾等虾类1亿尾。调查结果显示,牧场示范区富营养化程度有所降低,初级与次级生产力明显提升,其中海藻年生物量约为18 000 kg/hm~2;海洋牧场的渔业资源养护效果良好,人工鱼礁投放19个月后,鱼礁区游泳动物群落的物种丰富度、总生物量和总丰度分别为对照区的1.32倍、2.04倍和1.49倍。     

Forecasting the genetic influences of red drum stock enhancement in South Carolina

The South Carolina Department of Natural Resources (SCDNR) began stocking red drum, Sciaenops ocellatus (Linnaeus), in 1989 to augment the abundance of juveniles available for recreational harvest in South Carolina estuaries. While stock enhancement can help supplement wild populations under high fishing pressure, releasing hatchery‐raised fish into the wild also presents the risk of decreased genetic diversity. An individual‐based model (IBM) was developed to forecast the genetic influences of stocking on the wild spawning population to inform responsible stocking strategies. Model results indicated the SCDNR red drum stock enhancement programme should maintain mean contributions of stocked fish no greater than 30% per year class over a 45‐year stocking period, coupled with at least 10 effective breeders in the hatchery replaced annually, to maintain current levels of genetic diversity estimated in the wild population. The IBM is a useful tool for hatchery managers to guide responsible stock enhancement.     

A simple model for predicting ecological impacts of introduced aquatic organisms: a case study of common carp, Cyprinus carpio L., in the Sepik-Ramu River Basin, Papua New Guinea

Abstract Practical models for predicting the impacts of introduced biota are urgently required to assess the benefits and risks of introductions. The simple method described predicts the ecological consequences of an introduction through potential competition between species based on elementary niche classifications. The model's predictions are tested against field data for common carp, Cyprinus carpio L., which escaped from fish farms during a study of the feasibility of fish stock enhancement in a large river basin. Recorded effects of carp are based on pre- and post-carp gillnet catches, observations of local villagers, socio-economic censuses and other sources of data. The predicted ecological interactions of common carp are in broad agreement with those recorded. The method can assist pre-introduction assessments and is particularly useful where limited data exist. In this particular study, common carp have contributed significantly to an improved capture fishery by fortuitous accident; production from aquaculture was negligible. High niche overlap between carp and certain resident fish species is predicted and this may be of more consequence in highland than lowland regions. Organisms introduced/transferred for aquaculture should be assessed within a much wider forum. The intended impacts of an introduction/ transfer, which in the case study were entirely erroneous, is an area in need of considerable attention.     

Management of a highly unlikely native fish: The case of arctic charr Salvelinus alpinus from the Southern Alps

相似文献   

Potential effects of global warming on northern European freshwater fish and fisheries

Abstract Global warming is expected to result in considerable changes in northern European freshwater fish populations, fisheries and aquaculture. Shifts towards cyprinid and percid dominance in fish assemblages are expected, together with a decrease and collapse of salmonid and other coldwater fish populations. Most of the evident changes will occur in shallow lakes, where no thermal stratification occurs. The potential ranges of some fish species will shift northwards but pronounced changes will occur in the relative abundance of individual fish species. Total fish production will increase but because of changed composition of fish communities the commercial and recreational value of catches will decrease. Salmonid aquaculture productivity will increase provided that fish farmers adapt to new circumstances and cold, oxygenated water is available in larger quantities during summer.     

Evaluation of the effect of stock enhancement in the coastal waters of Guangdong,China

A total of 14.573 million fish fry and 96.32 million shrimp larvae were released across 31 locations into the coastal waters off Guangdong, China, in 2010. The released fish and shrimp were sampled through a combination of market and fishing log‐book surveys. The combined fishery production reached 362 868 kg. The input–output ratio was 1:5.99 for released fish (over 3 years) and 1:11.01 for released shrimp (over 2 years). The average increase in income was 721 RMB per capita. Approximately 240 thousand fish (after 3 years) and 1.2 million shrimp (after 2 years) survived to sexual maturity and could contribute to the spawning stock. The stockings were approximately one‐seventh of the fish and one‐half of the shrimp stocking carrying capacities, respectively. Based on these results, the intensity of stocking could be increased. Stocking and recapture strategies should be adjusted to align with the optimal stocking carrying capacity determined from this study.     

The balancing act of captive breeding programmes: salmon stocking and angler catch statistics

The debate over Atlantic salmon, Salmo salar L., stocking in Britain centres on the trade‐off between enhancing rod fisheries and harming wild populations. This article informs the debate by quantifying the relationship between stocking and angler catch statistics for 62 rivers over 15 years. After controlling for environmental factors affecting adult abundance, the 42 rivers with stocking had non‐significantly lower mean catch statistics than the 20 rivers without stocking. This difference increased with the age of stocked fish. Among stocked rivers, weak relationships between mean stocking effort and catch statistics also became more negative with the age of stocked fish. For stocked rivers, there was no evidence for a generally positive relationship between annual stocking efforts and catch statistics. Those rivers for which stocking appeared to improve annual rod catches tended to have lower than expected mean rod catches. The results suggest the damage inflicted on wild salmon populations by stocking is not balanced by detectable benefits to rod fisheries.     

我国鱼类近缘杂交研究及其在水产养殖上的应用

基因型不同的动物体间相互交配的过程称为杂交(hybridization)。杂交是被广泛采用的育种手段。杂交的主要目的在于获得杂种优势,并通过杂交选育新品种或新品系。根据杂交亲本的亲缘关系,杂交可分为远缘杂交(remote hybridization,distant hybridization)和近缘杂交(closehybrid     

西藏鱼类增殖放流初报

西藏土著鱼类生长缓慢、性成熟晚并对环境变化高度敏感。近年来,受过度捕捞、水利工程建设等人类活动的影响,西藏渔业资源面临越来越大的压力。开展增殖放流活动是恢复当地渔业资源和生态平衡的重要手段。本文介绍了西藏鱼类增殖放流概况、苗种来源、放流实施、效果评估情况,分析了目前存在的基础研究不足、苗种来源不稳定、缺乏技术规范、效果评估有待加强等问题。提出了加强增殖放流基础设施建设和基础理论研究、建立西藏鱼类增殖放流与效果评估技术规范、重视放流后的管理与评估工作、加强专业技术人才队伍建设的建议。     

Legislation and the capacity for rapid‐response management of nonindigenous species of fish in contiguous waters of Canada and the USA

• 1. The provision of Canadian and US hard, enforceable, law to authorize rapid response management of nonindigenous aquatic species originating from aquaculture, live fish sales, bait fish, and the pet trade was analysed at the provincial/state levels of government for the Atlantic, Laurentian Great Lakes, and Pacific regions of North America.
• 2. No federal legal capacity for rapid response management exists in either country. US state legislation is generally better developed than Canadian provincial laws to manage the exotic fish trade. However, much discrepancy exists among provincial and state law regarding provisions to restrict or prohibit potentially harmful species. Aquaculture and baitfish use is generally better regulated than live fish markets and the pet fish trade in both countries. Only the state of Maine has laws authorizing rapid‐response management to control escaped exotic fish.
• 3. Most species of nonindigenous fish arise from the aquarium, pet, and baitfish trades, and development of improved legislation containing provisions for rapid response management of escapees is warranted in all states and provinces.
• 4. It is recommended that Canada amends the Fisheries Act to create the appropriate enabling legislation to monitor, assess risk, and deploy rapid response management of nonindigenous aquatic species, including fish that enter federal fresh and sea waters. Two recently‐introduced US Bills, S. 725 and H.R. 1350, with their explicit measures for early detection and fast action response, could, if passed into law, create provisions to control introduced nuisance species throughout North American waters. They would also create precedents for states and provinces that have most jurisdiction over aquaculture and trade in exotic fish to amend and align their laws in a complementary manner.

Copyright © 2008 John Wiley & Sons, Ltd.     

Introduced and translocated fish species in the inland waters of Greece

Over the last 7 decades, 23 exotic fish species have been introduced into the inland waters of Greece. Some introductions were deliberately planned to take advantage of particular ecological or economic qualities of the species concerned. These include rainbow trout, Oncorhynchus mykiss (Walbaum), Pacific salmon, Oncorhynchus sp., vendace, Coregonus lavaretus (L.), grass carp, Ctenopharyngodon idella (Valenciennes), and silver carp, Hypophthalmichthys molitrix (Valenciennes). Other introductions, such as that of pumpkinseed, Lepomis gibbosus (L.), and false rasbora, Pseudorasbora parva (Temminck & Schlegel), were unintentional. Further transfers were made of species between various basins within the country, including common carp, Cyprinus carpio L., tench, Tinca tinca (L.), crucian carp, Carassius auratus gibelio (Bloch), bitterling, Rhodeus amarus (Bloch), and Aristotle's catfish, Silurus aristotelis Garman. Some species have become fully acclimatized and have built up important populations. In other cases, the transfers and introductions have had considerable negative impacts, particularly where introduced species have outcompeted native forms, as in the cases of the mosquito fish, Gambusia affinis (Baird & Girard), versus Greek toothcarp, Valencia letourneuxi (Sauvage), in the western Greek marshes, and of Aristotle's catfish versus the wels, Silurus glanis L., in Lake Volvi.     

Rapid dispersion of escaped meagre (Argyrosomus regius) from a coastal Mediterranean fish farm

Meagre (Argyrosomus regius) is an emerging species in aquaculture considered a locally absent species in the Western Mediterranean. Little is known about meagre escape incidents from farms. To evaluate escape impacts and develop mitigation measures, knowledge about the behaviour of escaped meagre is necessary. In this study, a rapid dispersion of escaped meagre was observed following a simulated escape incident in a coastal Mediterranean farm, using acoustic telemetry (acoustic tag: AT) and mark‐and‐recapture techniques (external tag: ET). A small proportion of AT meagre (22.7%) remained within the farm boundaries 24 h after the simulated escape. A total of 84 meagre (9.2%) were captured by local trammel netters nearby the farm facility within the first 48 h after escape. Only two AT individuals (15.3%) were detected by acoustic receivers located in coastal areas within 2 days after dispersal from the farm and eight ET meagre (0.8%) were recaptured along the shoreline during the first week. Two AT individuals (15.3%) were considered to be dead by predation few hours after escape. The rest of the AT individuals (N = 6, 46.2%) left the facility alive, and they were never detected by receivers nor reported back by fishermen. Thus, our results highlight the necessity of establishing escape mitigation strategies at Mediterranean fish farms, i.e. recapture programmes 24–48 h after the escape incident in collaboration with local fishermen, to diminish potential impacts related to meagre escapees.     

Critically examining the knowledge base required to mechanistically project climate impacts: A case study of Europe's fish and shellfish

An amalgam of empirical data from laboratory and field studies is needed to build robust, theoretical models of climate impacts that can provide science‐based advice for sustainable management of fish and shellfish resources. Using a semi‐systematic literature review, Gap Analysis and multilevel meta‐analysis, we assessed the status of empirical knowledge on the direct effects of climate change on 37 high‐value species targeted by European fisheries and aquaculture sectors operating in marine and freshwater regions. Knowledge on potential climate change‐related drivers (single or combined) on several responses (vital rates) across four categories (exploitation sector, region, life stage, species), was considerably unbalanced as well as biased, including a low number of studies (a) examining the interaction of abiotic factors, (b) offering opportunities to assess local adaptation, (c) targeting lower‐value species. The meta‐analysis revealed that projected warming would increase mean growth rates in fish and mollusks and significantly elevate metabolic rates in fish. Decreased levels of dissolved oxygen depressed rates of growth and metabolism across coherent species groups (e.g., small pelagics, etc.) while expected declines in pH reduced growth in most species groups and increased mortality in bivalves. The meta‐analytical results were influenced by the study design and moderators (e.g., life stage, season). Although meta‐analytic tools have become increasingly popular, when performed on the limited available data, these analyses cannot grasp relevant population effects, even in species with a long history of study. We recommend actions to overcome these shortcomings and improve mechanistic (cause‐and‐effect) projections of climate impacts on fish and shellfish.     

Pedigree analysis of recaptured fish in the stock enhancement program of spotted halibut Verasper variegatus

ABSTRACT:   Spotted halibut Verasper variegatus hatchery juveniles produced in 2002 were genotyped using three microsatellite DNA markers (msDNA) and then released into natural waters. Subsequently, recaptured individuals were examined using msDNA. In order to evaluate the effectiveness of the stock enhancement program, from the genetic point of view, a pairwise F _ST test was implemented to estimate the genetic divergence between the wild captive broodstock, the hatchery offspring and the recaptured samples. The analysis showed significant differentiation between the broodstock and recaptured samples. Pedigree determination using msDNA was used to calculate the effective population size of the recaptured stock, which was found to be very low ( N _e ≈ 8). Equal family survivability was observed between the two recaptured stocks, but not between the released and recaptured stock. The number of identified families was higher and more equalized in the hatchery offspring compared to the recaptured samples, where the number of families declined. This fact was caused by an unequal family survivability just before or just after release. Separately, the number of contributing parents to the hatchery offspring was lower than the broodstock census number. Consequently, these two facts caused the genetic divergence of the recaptured stock from the broodstock.