Genetic diversity and population structure of burbot Lota lota in Germany: Implications for conservation and management

The genetic structure of the gadiform fish species, burbot Lota lota L., was investigated across Germany to derive management options for facilitating the preservation of genetic diversity. Sequence analysis of the mitochondrial control region (n = 244) and microsatellite analysis (n = 861) of specimens from 20 sites revealed genetic structuring between major river basins, and particularly between lake and river habitats. The admixture zone between the Eurasian and West European phylogenetic clades in Lake Constance was confirmed and expanded to include the drainage basins of the rivers Rhine and Schlei/Trave. Haplotype distribution and private haplotypes in single river basins indicated population differentiation and imply that German burbot constituted an important part of the entire species' diversity. The derived genetic structuring has implications for future stocking programmes and the preservation of the adaptive potential of burbot, a guiding species for oligotrophic lakes in Europe.     

Winter movements of burbot (Lota lota) during an extreme drawdown in Bull Lake, Wyoming, USA

Winter movements of burbot (Lota lota) were monitored in Bull Lake, Wyoming during a record low water storage period in the winter of 1985–1986. Burbot with surgically implanted ultrasonic transmitters were commonly sedentary during the drawdown. The fish that did move were most active during dusk and at night in winter and during the day in spring. Burbot did not appear to occupy well defined home ranges or show discernible movement patterns. Movement into shallow water during winter was attributed to colder water temperatures and the onset of the spawning season. Burbot were always found associated with silt substrates during the drawdown. Aerial photographs of the exposed bottom revealed that virtually all suitable spawning and nursery habitat for burbot was eliminated by the 13.4-m drawdown.     

江鳕苗种培育技术研究

<正>江鳕(Lota lota Linnaeus)又名山鲶鱼、山怀子、山鳕,属鳕形目(Gadiformes)、鳕亚目(Ga-doidae)、鳕科(Gadidae)、江鳕属(Lata),是鳕科鱼中唯一的淡水种类。主要分布在45oN以北欧洲、亚洲和北美洲的内陆河湖和海湾处,在我国主要分布于黑龙江水系和新疆的额尔齐斯河水系以及鸭绿江上游。近年来由于环境污染,气候变暖和人为过度捕捞等因素导致自     

Public and stakeholder attitudes to the reintroduction of the burbot,Lota lota

Abstract Consideration of key sociological factors, including the views and attitudes of the local population, is critical to species reintroduction project success. This study examined the opinions of anglers, conservationists and the general public to a potential reintroduction of burbot, Lota lota L., to UK rivers. An online survey targeted the key stakeholder groups and a questionnaire was used to obtain a snapshot of public attitudes. In both studies, more than 90% of respondents supported reintroduction. Anglers, participants with prior knowledge of the species, males and respondents who were not a member of a conservation organisation, exhibited the most positive attitudes. Anglers and participants with prior knowledge of the species cited burbot as an angling opportunity, suggesting these groups view burbot as an exploitable resource. Overall, the surveys indicated that reintroduction of the burbot, should it be deemed feasible on ecological and biological grounds, would not be met by major public opposition.     

Isolation and experimental challenge of cultured burbot (Lota lota maculosa) with Flavobacterium columnare and Aeromonas sp. isolates

Burbot (Lota lota maculosa) are a potential new species for commercial aquaculture. As burbot culture expands, there is a need to further define pathogen susceptibility and characterize aspects of the burbot immune response in an effort to assess fish health. A recent clinical diagnostic case from juvenile burbot reared at a commercial production facility resulted in the isolation and identification of Flavobacterium columnare along with several Aeromonas spp. The F. columnare isolate was assigned to genetic group 1 via multiplex PCR, a genetic group commonly associated with columnaris disease cases in rainbow trout (Oncorhynchus mykiss). Virulence of the F. columnare isolate was assessed in vivo in both juvenile burbot and rainbow trout. Additionally, several of the Aeromonas sp. case isolates were identified via sequencing (16S rRNA, gyrB and rpoD) and a putative A. sobria isolate (BI-3) was used to challenge burbot, along with a known virulent Aeromonas sp. (A141), but BI-3 was not found to be virulent. Burbot were refractory to F. columnare when challenged by immersion, and it is likely that this is a secondary pathogen for burbot. Although refractory in burbot, the identified F. columnare isolate (BI-1) was found to be virulent in rainbow trout.     

Empirical estimation of recreational exploitation of burbot,Lota lota,in the Wind River drainage of Wyoming using a multistate capture–recapture model

Burbot, Lota lota (Linnaeus), is a regionally popular sportfish in the Wind River drainage of Wyoming, USA, at the southern boundary of the range of the species. Recent declines in burbot abundances were hypothesised to be caused by overexploitation, entrainment in irrigation canals and habitat loss. This study addressed the overexploitation hypothesis using tagging data to generate reliable exploitation, abundance and density estimates from a multistate capture–recapture model that accounted for incomplete angler reporting and tag loss. Exploitation rate μ was variable among the study lakes and inversely correlated with density. Exploitation thresholds μ₄₀ associated with population densities remaining above 40% of carrying capacity were generated to characterise risk of overharvest using exploitation and density estimates from tagging data and a logistic surplus‐production model parameterised with data from other burbot populations. Bull Lake (μ = 0.06, 95% CI: 0.03–0.11; μ₄₀ = 0.18) and Torrey Lake (μ = 0.02, 95% CI: 0.00–0.11; μ₄₀ = 0.18) had a low risk of overfishing, Upper Dinwoody Lake had intermediate risk (μ = 0.08, 95% CI: 0.02–0.32; μ₄₀ = 0.18) and Lower Dinwoody Lake had high risk (μ = 0.32, 95% CI: 0.10–0.67; μ₄₀ = 0.08). These exploitation and density estimates can be used to guide sustainable management of the Wind River drainage recreational burbot fishery and inform management of other burbot fisheries elsewhere.     

Recruitment of burbot (Lota lota L.) in Lake Erie: an empirical modelling approach

Stapanian MA, Witzel LD, Cook A. Recruitment of burbot (Lota lota L.) in Lake Erie: an empirical modelling approach.
Ecology of Freshwater Fish 2010: 19: 326–337. Published 2010. This article is a US Government work and is in the public domain in the USA Abstract – World‐wide, many burbot Lota lota (L.) populations have been extirpated or are otherwise in need of conservation measures. By contrast, burbot made a dramatic recovery in Lake Erie during 1993–2001 but declined during 2002–2007, due in part to a sharp decrease in recruitment. We used Akaike’s Information Criterion to evaluate 129 linear regression models that included all combinations of one to seven ecological indices as predictors of burbot recruitment. Two models were substantially supported by the data: (i) the number of days in which water temperatures were within optimal ranges for burbot spawning and development combined with biomass of yearling and older (YAO) yellow perch Perca flavescens (Mitchill); and (ii) biomass of YAO yellow perch. Warmer winter water temperatures and increases in yellow perch biomass were associated with decreases in burbot recruitment. Continued warm winter water temperatures could result in declines in burbot recruitment, particularly in the southern part of the species’ range.     

First feeding of burbot, Lota lota (Gadidae, Teleostei) larvae under different temperature and light conditions

The burbot (Lota lota) is the only fresh water member of the cod family, Gadidae, and is adapted to cold waters. The effects of temperature and light on the growth and survival of burbot larvae were investigated under hatchery conditions. Three temperature regimes (12, 16 and 20°C) were applied under continuous light and darkness during the experiment. Rotifer, Brachionus calyciflorus (L.) were fed to the larvae in the first 10 days and the diet was then replaced with Artemia nauplii. At the end of the feeding stage with rotifer, growth in terms of the total length and wet weight were larger at higher temperatures under continuous light. At day 10, survival rates of the fish held at 12°C under continuous light and darkness regime were higher than those held at 16°C and 20°C kept under the same conditions. From day 10 onwards, larval growth improved remarkably after changing the live food from rotifer to Artemia in all treatments. At the end of the study, the highest survival rate was recorded among the larvae held at 12°C exposed to continuous light. Under light condition, the temperature of 20°C did not result in an improved larval growth compared with 16°C. This may indicate that high temperature and continuous light are not beneficial for larval growth and survival when they reach older stage of development. The results indicate a significant interaction for the combination of temperature, light and time with respect to survival and wet weight, making unambiguous interpretation of the main effects difficult.     

The effect of meal size on the rate of gastric evacuation of burbot, Lota lota (L.)

Abstract– The effect of meal size on the gastric evacuation rate of burbot Lota lota (L.), was determined at a constant temperature of 1.5°C. Burbot were fed vendace Coregonus albula (L.), in varying amounts from 1.0% to 12.6% of burbot weight. Although gastric evacuation rate decreased exponentially with increasing meal size, the absolute amount of food evacuated per day (g. day⁻¹ increased when meal size increased. The estimated maximum daily gastric evacuation rates were 0.8, 1.3 and 1.6 g/day with meal sizes 1%, 5% and 10% of burbot weight (200 g). No difference in gastric evacuation rate was observed between meals of the same size (8 g) but which consisted of either one or three vendace.     

Variations in the activity of digestive enzymes along the intestine of the burbot Lota lota expressed by different methods

The activities of major digestive hydrolases (proteases, amylase, lipase and esterases) along the intestine were studied in the burbot Lota lota (L.) using different methods of activity expression. The enzyme activities were determined both in the whole gut segments and in the isolated mucosa, and then expressed in terms of tissue mass and protein content in the samples. Further, the cumulative activities of these enzymes in the pyloric caeca were compared with those in the rest of the intestine to estimate the overall contribution of these regions to digestion. The data obtained suggest the essential role of the pyloric caeca in the digestion of the burbot. In addition, the variations in the pH values along the intestine and the changes in the enzyme activities with incubation temperature were examined. The study proved the method of enzyme activity expression to be a key factor influencing the outcome of the experiment.     

The effect of age,size and digestive tract development on burbot,Lota lota (L.), larvae weaning effectiveness

The effect of burbot weight (BW) and length (TL) on the efficiency of weaning under controlled conditions was investigated. Growth, survival rate, cannibalism and histological analysis of digestive tract were examined. The experiment lasted 49 days (40–89 days post hatch [DPH]). The fish (BW 0.12 g; TL 14.1 mm) were divided into four groups: a control group (C) exclusively fed Artemia sp. nauplii and groups F40, F47 and F54 that were weaned to dry feed on 40, 47 and 54 DPH, respectively. The highest survival rate was observed in groups C (78%) and F54 (58%). In group F54, similar TL (53.8 mm) and higher BW (1.36 g) at the end of experiment, in comparison with group C (43.9 mm, 0.84 g for TL and BW, respectively), were obtained. At the end of the experiment, the length of enterocytes in groups C and F54 was at a similar level (over 23 μm), whereas in group F47 was significantly lower (approximately 20 μm; P < 0.05). This study for the first time presents successful weaning of the burbot. The data indicate that live food should be offered until the fish reach 25 mm and 0.20 g.     

Diet overlap between young-of-the-year perch, Perca fluviatilis L., and burbot, Lota lota (L.), during early life-history stages

Abstract –  The diet overlap between young-of-the-year (YOY) perch and burbot in the pelagic zone of Lake Constance during spring and summer was investigated in relation to gape size limitation. Because perch were larger and grew faster than burbot during their early life history, perch overcame gape size limitation for various zooplankton taxa earlier than burbot. The interspecific diet overlap between perch and burbot decreased continuously until June, but increased slightly, when burbot became able to feed on large daphnids by the beginning of July. All zooplankton taxa could be found within perch stomachs by the middle of June, when perch overcame gape size limitation for large cladocerans. However, there was an increasing tendency for individual diet specialisation of perch, as the similarity between individual perch stomach contents decreased. In contrast, the similarity between individual burbot stomach contents remained at almost 50% until the end of August, indicating that all burbot rely on cyclopoid copepods during their entire pelagic life-history stage. Because by July YOY perch are more abundant by one order of magnitude in the pelagic zone than burbot, YOY perch may be more affected by intraspecific competition than by interspecific competition with burbot. Burbot, on the other hand, may evade strong competition with YOY perch by performing diel vertical migrations, thus being restricted to feed on migrating zooplankton prey.     

Determination of the optimal feeding rate and light regime conditions in juvenile burbot, Lota lota (L.), under intensive aquaculture

The aim of the study was to optimize burbot juveniles rearing in recirculating aquaculture system. In experiment 1 (17 °C, photoperiod 24L:0D), the fish (initial: body weight [W] = 15.36 ± 3.72 g, standard length [SL] = 12.48 ± 1.09 cm) were divided into four groups (I, II, III and IV). Different feeding levels were applied: 1, 2, 3 and 4 % of biomass daily (counted based on dry feed weight). The feed conversion ratio (FCR) and specific growth rate (SGR) were recorded. In experiment 2 (17 °C, feeding level of 2 % of biomass day^?1), fish (W = 5.24 ± 2.43 g and SL = 8.54 ± 1.24 cm) were divided into two groups where different light conditions were applied (I: 24 h light [1,800 lx] and II: 24 h darkness [4 lx]). In experiment 1, the highest SGR was recorded in group II (1.93 % day^?1), whereas the lowest SGR (1.27 % day^?1) and final W (P < 0.05) was in I group. The lowest (P < 0.05) FCR (0.63) was in group II. In the remaining groups, FCR was similar (0.68–0.70, P > 0.05). The feed consumption in group I reached 100 %, in group II, it was 71.3 % (P < 0.05) and it was the lowest in groups III (39.26 %) and IV (36.93 %). In experiment 2 no differences in the growth and survival rate were recorded (final SL between 14.16 and 14.19 cm, P > 0.05; W between 23.33–23.35 g; P > 0.05). The results from experiment 1 indicate that the feeding 2 % of biomass day^?1 was the most efficient. Also, it was proven, for the first time, that there was no effect of using different constant light conditions.     

Characterization of susceptibility and carrier status of burbot,Lota lota (L.), to IHNV,IPNV, Flavobacterium psychrophilum,Aeromonas salmonicida and Renibacterium salmoninarum

In this study, susceptibility and potential carrier status of burbot, Lota lota, were assessed for five important fish pathogens. Burbot demonstrated susceptibility and elevated mortality following challenge with infectious haematopoietic necrosis virus (IHNV) by immersion and to Aeromonas salmonicida by intraperitoneal (i.p.) injection. IHNV persisted in fish for at least 28 days, whereas A. salmonicida was not re-isolated beyond 17 days post-challenge. In contrast, burbot appeared refractory to Flavobacterium psychrophilum following intramuscular (i.m.) injection and to infectious pancreatic necrosis virus (IPNV) by immersion. However, i.p injection of IPNV resulted in re-isolation of virus from fish for the duration of the 28 day challenge. Renibacterium salmoninarum appeared to induce an asymptomatic carrier state in burbot following i.p. injection, but overt manifestation of disease was not apparent. Viable bacteria persisted in fish for at least 41 days, and bacterial DNA isolated by diagnostic polymerase chain reaction was detected from burbot kidney tissue 90 days after initial exposure. This study is the first to investigate susceptibility of burbot to selected fish pathogens, and this information will aid in efforts to culture and manage this species.     

乌苏里江上游虎头江段江鳕捕捞群体结构特性的研究

2003年5、10月对乌苏里江上游虎头江段江鳕进行种群结构及生物学特性调查研究，通过对60尾样本分析，结果表明：乌苏里江上游虎头江段江鳕W=0．0195L^2．7022(r=0．8991)，性比(♀：♂)为1．2：1。种群结构低龄个体所占比例明显偏高，年龄组成以2^ -3^ 为主，4^ 以上个体较少，种群低龄化现象严重，生殖群体组成单一，基本由第一次性成熟个体组成，种群数量2002年7．8t，2003年7．5t。目前乌苏里江上游虎头江段江鳕的资源状况处于下降状态。     

Modelling the population viability of a threatened amphibian with a fast life‐history

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