Using genetic methods for analysis of fish meals and feeds employed in Greek mariculture

Large quantities of high protein fish meals are needed to sustain cultured species and thus the impact to marine ecosystem has been highly discussed. The aim of this study was to apply a PCR‐cloning methodology for a robust insight into the composition of commercial fish meals and feeds for farmed species of the Greek mariculture, assessing the risk posed by aquaculture to marine ecosystems but also the risk posed by commercial fish feeds to the increase in trophic level of species farmed in Greece. 89% of the sequences were identified to species level and only 11% to genus/family level. Overall, a total of 49 taxa were identified (44 fish species/taxon, five non‐fish species/taxon). Even though small pelagic fish like Engraulis sp. were the main portion, a wide range of species constituted the fish meals and feeds. Plant and animal species were also detected as an alternative protein source. Feed products employed in Greek mariculture still contain large portions of fish meals which increase the mean trophic level of farmed species causing a farming up trend. The results emphasize that such molecular methodologies are needed to certify aquafeeds allowing fish feed producers to demonstrate their commitment to sustainable aquaculture.     

渤海鱼类群落结构及其主要增殖放流鱼类的资源量变化

基于2010年5月和8月渤海渔业调查数据,结合1959年以来渤海鱼类相关文献资料,对渤海鱼类群落结构的演替、主要增殖放流鱼类的资源动态作了初步分析.结果表明,渤海鱼类群落优势种由个体大、营养层次高的带鱼Trichiurus haumela、半滑舌鳎Cynoglossus semilaevis等优质底层鱼类逐渐被黄鲫Setipinna taty、鳀Engra ulis ja ponicus等个体小、营养层次低的小型中上层鱼类所替代,并且除黄鲫外,其他小型鱼类优势种也在不断更替中.另外,生物健康度指数(BHI)分析显示,渤海鱼类群落处于相对不稳定状态.鱼类资源量急剧降低,尤其在5月,CPUE由1959年的186 kg/h下降至目前不足1 kg/h,鱼类资源密集区主要分布在莱州湾、渤海湾和渤海中部,而辽东湾分布相对较少,并且鱼类资源与海蜇呈交错分布.近年来,渤海增殖放流的鱼类仅有花鲈Lateolabrax japonicus和许氏平鲉Sebastes schlegeli的资源量有小幅度回升,其他种类从20世纪80年代开始资源量一直处于下降趋势.从渤海鱼类群落结构的演替和增殖放流鱼类的资源量变化来看,渤海鱼类群落依旧是小型经济价值较低的种类控制其能流结构.除花鲈外,其他增殖放流鱼类的资源量均不足历史最高资源量的1％,其资源量的恢复尚有很大的空间,增殖潜力很大.     

Direct interaction between wild fish aggregations at fish farms and fisheries activity at fishing grounds: a case study with Boops boops

Coastal aquaculture installations concentrate large numbers of wild fish species of both ecological and economic importance, including schools of bogue, Boops boops (L.), in high abundance and biomass. The aggregated species consume large quantities of the easily available pellets lost from cages. As a consequence, the physical condition of farm‐associated wild fish is increased and their physiology is altered. These changes may influence local fisheries as many of these aggregating species are targeted by fishers. We assess whether local fishers catch wild fish that have previously aggregated at fish farms by comparing the body condition, trophic indexes, diet overlap and the fatty acid (FA) composition of B. boops obtained from local fish markets and around fish farms. Bogue captured by trammel‐nets and around fish farms facilities presented a similar biological condition, as well as high quantities of pellets in the gut, and their FA profile was affected by vegetal‐derived FAs. In contrast, bogue captured by trawlers were not influenced by fish farms, as they consumed natural trophic resources. We conclude that artisanal fishers exploit these aggregated fish populations once they have dispersed away from farms, and benefit from a ‘biomass export’ from fish farms at a local scale.     

Productivity and recovery of forage fish under climate change and fishing: North Sea sandeel as a case study

Forage fish occupy a central position in marine food‐webs worldwide by mediating the transfer of energy and organic matter from lower to higher trophic levels. The lesser sandeel (Ammodytes marinus) is one of the ecologically and economically most important forage fish species in the North‐east Atlantic, acting as a key prey for predatory fish and sea birds, as well as supporting a large commercial fishery. In this case study, we investigate the underlying factors affecting recruitment and how these in turn affect productivity of the North Sea sandeel using long‐term data and modelling. Our results demonstrate how sandeel productivity in the central North Sea (Dogger Bank) depends on a combination of external and internal regulatory factors, including fishing and climate effects, as well as density dependence and food availability of the preferred zooplankton prey (Calanus finmarchicus and Temora longicornis). Furthermore, our model scenarios suggest that while fishing largely contributed to the abrupt stock decline during the late 1990s and the following period of low biomass, a complete recovery of the stock to the highly productive levels of the early 1980s would only be possible through changes in the surrounding ecosystem, involving lower temperatures and improved feeding conditions. To that end, we stress the need for ecosystem‐based management accounting for multiple internal and external factors occurring within the broader context of the ecosystem in which forage fish species, such as sandeel, play an important and integral part.     

Hundred-year decline of North Atlantic predatory fishes

We estimate the biomass of high‐trophic level fishes in the North Atlantic at a spatial scale of 0.5° latitude by 0.5° longitude based on 23 spatialized ecosystem models, each constructed to represent a given year or short period from 1880 to 1998. We extract over 7800 data points that describe the abundance of high‐trophic level fishes as a function of year, primary production, depth, temperature, latitude, ice cover and catch composition. We then use a multiple linear regression to predict the spatial abundance for all North Atlantic spatial cells for 1900 and for each year from 1950 to 1999. The results indicate that the biomass of high‐trophic level fishes has declined by two‐thirds during the last 50‐year period, and with a factor of nine over the century. Catches of high‐trophic level fishes increased from 2.4 to 4.7 million tonnes annually in the late 1960s, and subsequently declined to below 2 million tonnes annually in the late 1990s. The fishing intensity for high‐trophic level fishes tripled during the first half of the time period and remained high during the last half of the time period. Comparing the fishing intensity to similar measures from 35 assessments of high‐trophic level fish populations from the North Atlantic, we conclude that the trends in the two data series are similar. Our results raise serious concern for the future of the North Atlantic as a diverse, healthy ecosystem; we may soon be left with only low‐trophic level species in the sea.     

Impaired littoral energy pathways cause a shift to pelagic resources by fish in recovering lake food webs

Fish communities may increase in biomass and productivity due to energy subsidies from the littoral invertebrate community. In lakes recovering from acidification and metal contamination, such as those in Sudbury, Ontario, Canada, impaired benthic invertebrate communities (i.e., low diversity with higher abundance of small‐bodied taxa) allowed a critical test of the role of these littoral pathways on fish diet. We compared fish abundance, diversity, diet and biomass in eight recovering and eight reference lakes and related availability of the main littoral and pelagic invertebrate groups to fish diet regime using stable isotope analysis. A Bayesian mixing model (MixSIR) was used to estimate diet likelihood, and convex hull analysis was used to estimate trophic niche space of fish communities. Fish biomass did not differ between impaired and reference lakes despite substantial differences in potential diet. Fish depended strongly on littoral benthos in the reference lakes but consumed more pelagic food in the impaired lakes. The trophic niche of the focal, most common fish species (i.e., yellow perch, smallmouth bass, pumpkinseed and brown bullhead) was larger in the impaired lakes. We attributed these differences to low diversity at the highest trophic levels of fish communities in the impaired lakes as well as to depauperate benthic invertebrate communities. In contrast to the food webs of most temperate lakes, fish in impaired lakes preyed less on littoral invertebrates yet still managed to maintain a reference lake level of biomass standing crop by relying more on pelagic resources – macro zooplankton such as Chaoborus.     

Shifting trophic architecture of marine fisheries in New Zealand: Implications for guiding effective ecosystem‐based management

New Zealand has led the world in restoration of marine fisheries since the introduction of the Quota Management System in 1986, but challenges remain in minimizing the ecosystem‐level effects of industrialized fishing. We analysed existing long‐term fisheries data sets from 1931 to 2015 in New Zealand to resolve trends in important ecological properties of major exploited fish communities. Increases in community dissimilarities of catch composition in 1931 and 1972, followed by increasing total landings, highlight major expansions of fishing grounds and exploited species during these periods. Mirroring global patterns, the remarkable rise in fishing power, demand and generation of new markets in New Zealand have all contributed to this expansion. Marine Trophic Indices (MTIs) of landings have decreased together with total catch after the year 2000, reflecting smaller catches with a higher composition of lower trophic‐level species in recent years. Differences in relative abundance of species estimated between fisheries‐dependent and fisheries‐independent data were observed, where high‐value species displayed better agreement in relative abundance between data sets. Despite being under a Quota Management System, temporal development of MTI values relative to the timing of industrial expansion of fisheries was remarkably similar to those observed in the North Sea and Brazil, with a single expansion and decline. MTI values presented better long‐term stability in the US fisheries analysed. Analysis of long‐term data and the development of well‐resolved ecological baselines will be the first step towards applying EBM to New Zealand fisheries, in keeping with global trends in fisheries management.     

渤海鱼类群落功能群及其主要种类

根据2009年8月和10月对渤海渔业资源的底拖网调查,采用胃含物分析、聚类分析和功能群划分的方法研究了渤海鱼类群落的功能群组成及其主要种类。结果表明,渤海夏、秋季鱼类群落包括7个功能群,分别为浮游动物食性功能群、杂食性功能群、底栖动物食性功能群、虾食性功能群、虾/鱼食性功能群、鱼食性功能群和广食性功能群;其中主要功能群为浮游动物食性功能群、杂食性功能群和虾/鱼食性功能群;主要种类有小黄鱼、蓝点马鲛、斑、赤鼻棱鳀、银鲳和黄鲫。圆筛藻、中华哲水蚤、太平洋磷虾、长额刺糠虾、中国毛虾、甲壳类幼体、日本鼓虾、六丝矛尾虎鱼、小黄鱼、双壳类和腹足类是当前渤海夏、秋季鱼类群落的主要饵料种类。     

渔获物平均营养级在渔业可持续性评价中的应用研究进展

高强度的捕捞努力量和渔业管理不力等因素导致全球范围内传统渔业资源的衰退,近年来渔获物平均营养级(MTL,mean trophic level)作为以生态系统为基础的渔业管理评价指标被普遍应用。本文在广泛收集国内外相关文献资料基础上,系统地介绍了MTL在渔业资源评价中的研究进展。已有研究显示,MTL能够利用已知渔获数据来分析,且参数化较为简便,在评价渔业可持续性中优势明显。受以渔获量作为生态系统指标、营养级(TL,trophic level)随体长的变化、渔获统计数据质量、低TL种类的过多捕捞和海域环境富营养化等因素的影响,在评估渔业资源利用状况时,需将MTL与剔除TL小于3.25物种下的3.25MTL、渔业均衡指数(FIB)等营养指标综合分析。此外,综合运用多指标,将营养指标与渔获组成、中上层鱼类与底层鱼类产量的比值、市场价格等指标结合分析,有助于掌握引起MTL变动的因素,更加全面地掌握捕捞活动下鱼类群落结构的实际变化状况。     

Gear-based management of a tropical artisanal fishery based on species selectivity and capture size

The population density, species composition and lengths of fish landed by artisanal fishermen using six types of gear: large and small traps, gill nets, hand lines, spears and beach seines were studied in the multi‐species fishery of southern Kenya. Selectivity and catch composition among gears were determined by studying the species richness, diversity, size and mean trophic level of the catches for each gear type, to develop gear‐based management recommendations for this artisanal reef lagoon fishery. One hundred and sixty‐three reef and reef‐associated species from 37 families were recorded in the catch. Beach seines and small traps accounted for the highest number of fish landed (34–35 individuals per fisherman per day). These gears also caught smaller fish than big traps, spears and gill nets. Beach seines caught the highest number of species (14 ± 7 species per day) while most other gears caught four to five species per day with no differences between gears. Predatory species with a mean trophic level of 3.6 dominated catches from hand lines, while the mean trophic level of the other gears was low and ranged from 2.6 to 2.9 with no differences between the gears. The high diversity and small size of fish caught in beach seines indicates that its selectivity overlapped most with large traps and gill nets. Spears and small traps also showed high similarity in species selectivity and small traps captured the smaller mean size of fish, indicating that they are likely to pre‐empt the resource of spears. Large traps, hand lines and spears catch the largest individuals and the species composition of the catch differed sufficiently such that their selectivity should overlap the least and may, therefore, be the preferred mix of gears. The elimination or reduction of beach seines and small traps should reduce the catch of small fish and overlap in selectivity among the existing gears.     

渤海主要生物种间关系及食物网的研究↑（*）

根据１９９２年－１９９３年渤海增殖生态基础调查大面定点底拖网试捕的渔获物，对渤海２７种鱼类和１０种虾蟹类的３８０１个胃含物样品进行了分析，并与１０年前渤海鱼类的食性进行了比较。结果表明：蓝点马鲛、小黄鱼和白姑鱼等主要捕食鱼类胃含物中鱼的比例较１０年前明显增加，鱼类的食性类型无明显变化。渤海低级肉食性鱼类的营养级由１９８２－１９８３年的平均２．４上升为２．５，中、高级肉食性鱼类的营养级分别由原来的平均３．２和３．８降为２．８和３．３。渤海主要鱼类之间饵料重叠系数大于０．６的占１５％。鱼为渤海多数中、高级肉食性鱼类的主要摄食对象。     

基于碳、氮稳定同位素研究黄海及东海北部主要鱼类的营养级和食性

本研究通过对2011~2014年间在黄海及东海北部采集的36种海洋鱼类进行碳、氮稳定同位素测定,利用碳稳定同位素比值(δ¹³C)计算底层饵料贡献比(Bp)来确定鱼类的食性,利用氮稳定同位素比值(δ¹⁵N)计算其营养级(TL)。结果显示,这36种鱼类的营养级范围为2.75~4.34,平均值为3.47。其中,4种为完全浮游生物食性,8种为底栖生物食性,完全底栖生物食性为12种,混合食性为12种。中(TL=3.5~4)、低(TL<3.5)营养级的种类占大多数(91.67%),而高营养级(TL>4)种类较少,仅为3种,且全部为混合食性。营养级的研究结果与1986、1992和2004年的研究对比发现,个别种类发生了改变。如蓝点马鲛(Sconberonorus niphonius)营养级有不同程度的下降;而黄鲫(Setipinna t)aty却有不同程度的上升。食性的研究结果与2004、2009和2011年的研究对比发现,有些种类食性发生了较大变化,如白姑鱼(Argyrosomus argentatus);有些种类食性几乎没有变化,如小黄鱼(Larimichthys polyactis)。     

Interspecific competition between restocked 0+ salmon parr (Salmo salar) and native fish species in a large European river

Atlantic salmon populations have experienced strong declines in most large European rivers. In the Loire Basin, France, a major restocking effort has been carried out on the Allier River to reduce the wild population decline. This study aimed at investigating the trophic insertion of hatchery‐reared salmon parr and whether they compete for resources with native fish species. For this purpose, two riffles located in the upstream and downstream parts of the restocked area have been surveyed monthly following the initial 0+ salmon fry release. 0+ parr densities remained high upstream, with autumnal values greater than those recommended to maximise smolt production. In contrast, downstream densities declined to weak values despite a faster increase in size, probably mainly due to summer temperatures rising above the discomfort threshold. By analysing the vulnerability to predation of ingested invertebrate prey, we highlighted the role of habitat constraints in driving most of the different fish species to a likely opportunistic utilisation of available food resources. As a result, species such as stone loaches and barbel juveniles exhibited narrow trophic niches and high overlaps with 0+ parr. Nonetheless, both abundant prey resources and spatial or temporal habitat segregation have limited interspecific competition, enabling competitive coexistence of sympatric species, except for barbel juveniles in certain circumstances. Therefore, our findings suggest that future restocking programmes should carefully consider the thermal and hydraulic conditions regarding further smolt production as well as their general trophic context, according to the potential inconvenience of restocked salmon fry arrival relative to native species.     

Competition between farmed and wild fish: The French sea bass and sea bream markets

ABSTRACT

Aquaculture is contributing at an increasing rate to the world seafood supply. The interaction between fisheries and aquaculture is especially important for the seafood market where supply of wild and farmed fish can affect price dynamics. We examine market interactions in the French fresh sea bass and sea bream markets. We test for long-term price parity between farmed and wild products for these two species, applying a bivariate cointegration approach to market delineation. We also conduct the Law of One Price (LOP) test between price series. Our data base consists of monthly domestic price series for fish purchased by French households from 2007 to 2012. Our empirical results show that the fresh fish markets for whole wild and farmed sea bream are partially integrated, yet those for whole wild and farmed sea bass are not integrated. The substantially higher price for wild sea bass relative to farmed sea bass suggests that consumers may be more sensitive to seafood production processes when it comes to higher-value species.     

黄海北部鱼类群落的摄食生态及其变化

根据2010年5月和8月对黄海北部渔业资源的底拖网调查,分析了黄海北部鱼类群落的摄食生态及其变化.结果表明,黄海北部鱼类群落共有9种重要种类,与5月相比,8月没有游泳动物食性鱼类,广食性鱼类减少,浮游动物食性鱼类的比例大大增加.黄海北部鱼类群落在5月和8月总摄食量分别为0.5万t和19.6万t,细长脚虫戎、中华哲水蚤、脊腹褐虾、中华安乐虾、小黄鱼和鳀是黄海北部鱼类群落被摄食量最高的6种主要饵料种类.1985年至2010年的25年间,黄海北部鱼类群落的优势种更替,游泳动物食性鱼类减少,广食性鱼类增多；鱼类群落的平均营养级每10年下降0.24,尽管近10年的下降速度有所放慢,但仍远远高于渤海和黄海中南部的下降速度.     

Price cointegration in spatial markets: An application to milkfish markets in Taiwan

Abstract

The objectives of this study are to analyze the interdependent behavior of lead‐lag milkfish price adjustments between vertically‐related markets (from production to consumption) as well as between five major horizontally‐related wholesale markets. Empirical results show that there is a two‐way lead‐lag cointegrating price relationship between milkfish wholesale and retail markets. Since the fish wholesale market cannot completely and quickly assimilate the retail market information, the speed of response of wholesale prices to retail price changes is relatively slow, inducing low pricing efficiency. The Taipei wholesale market appears to cause the greatest leadership impact on the milkfish price formation compared to other wholesale markets in both the long‐run and short‐run. The results also reveal that there is a high degree of integration relationship between the horizontally integrated wholesale markets (Chiayi, Changhwa and Taichung) for milkfish in the southwestern region within a short distance.     

Impacts of climate change on the complex life cycles of fish

To anticipate the response of fish populations to climate change, we developed a framework that integrates requirements in all life stages to assess impacts across the entire life cycle. The framework was applied on plaice (Pleuronectes platessa) and Atlantic herring (Clupea harengus) in the North Sea, Atlantic cod (Gadus morhua) in the Norwegian/Barents Seas and European anchovy (Engraulis encrasicolus) in the Bay of Biscay. In each case study, we reviewed habitats required by each life stage, habitat availability, and connectivity between habitats. We then explored how these could be altered by climate change. We documented environmental processes impacting habitat availability and connectivity, providing an integrated view at the population level and in a spatial context of potential climate impacts. A key result was that climate‐driven changes in larval dispersion seem to be the major unknown. Our summary suggested that species with specific habitat requirements for spawning (herring) or nursery grounds (plaice) display bottlenecks in their life cycle. Among the species examined, anchovy could cope best with environmental variability. Plaice was considered to be least resilient to climate‐driven changes due to its strict connectivity between spawning and nursery grounds. For plaice in the North Sea, habitat availability was expected to reduce with climate change. For North Sea herring, Norwegian cod and Biscay anchovy, climate‐driven changes were expected to have contrasting impacts depending on the life stage. Our review highlights the need to integrate physiological and behavioural processes across the life cycle to project the response of specific populations to climate change.     

Economic feasibility of high Omega-3 soybean oil in mariculture diets: A sustainable replacement for fish oil

ABSTRACT

The growth of global aquaculture has put intense pressure on sources of fish oil and fishmeal for aquafeeds. The nutraceuticals industry has added further pressure on fish oils with high Omega-3 fatty acids. GM soybeans could provide substitutes in high Omega-3 soybean oil (STA oil), as well as soy protein concentrate (SPC). This article examines the technological and economic feasibility of substituting STA oil for one-half the fish oil in the diet of Seriola rivoliana, a species often destined for sushi markets. Previous studies have shown that the substitution results in no change in flesh quality or consumer acceptance. We find that the two feed technologies result in essentially identical growth pattern and feed consumption. Economic feasibility depends upon the price of STA oil being lower than the price of fish oil. Based on our market analysis, we estimate that STA oil will enter the market at a price about two-thirds of the fish oil price. The estimated cost savings at these prices are small, a 2.8% reduction in feed costs and 0.9% reduction in total costs. However, the potential global market for STA oil could be as much as 252 thousand metric tons annually, which would require soybean production equivalent to that from 1.63% of current U.S. soybean area.     

Polychaetes as indicators of marine fish farm organic enrichment

Marine fish farms cause environmental disturbance of sediment due to uneaten food and fish faeces that accumulate on the sea bottom. These products give rise to organic enrichment followed by degradation processes; reduction of level of dissolved oxygen in the bottom water; generation of high levels of sulfides; changes of benthic assemblages and even azoic conditions. The soft bottom benthic communities and, above all, the polychaetes are considered good indicators of environmental perturbations considering their relatively fast changes in diversity and abundance and because their trophic flexibility and life-history traits are considered a pre-adaptation to the condition of disturbed habitats. The aim of the present study is to evaluate the polychaete population changes as a result of organic enrichment produced by a marine fish farm. The study was carried out on a fish farm located in the coastal water of Porto Ercole (Tyrrhenian Sea) with two submersible sea cages and a year production of 180 tonnes. The macrobenthos samples were collected during four campaigns (July and December 2001, May and October 2002). The results showed: 1) a rapid change of the assemblage located beneath the cages related to the fish biomass reared and a high dominance of the opportunistic Capitella spp.; 2) limited sediment disturbance close to cages (20–50 m); 3) no effect in the area 50 m beyond the cages. Two months after the fish harvest and thus reduction of organic enrichment, perturbated assemblages showed signals of recovery like species richness increase and reduction of opportunistic species.