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.
Temperature affects many aspects of performance in poikilotherms, including how prey respond when encountering predators. Studies of anti-predator responses in fish mainly have focused on behaviour, ...whereas physiological responses regulated through the hypothalamic-pituitary-interrenal axis have received little attention. We examined plasma cortisol and mRNA levels of stress-related genes in juvenile brown trout (
) at 3 and 8 °C in the presence and absence of a piscivorous fish (burbot,
).
A redundancy analysis revealed that both water temperature and the presence of the predator explained a significant amount of the observed variation in cortisol and mRNA levels (11.4 and 2.8%, respectively). Trout had higher cortisol levels in the presence than in the absence of the predator. Analyses of individual gene expressions revealed that trout had significantly higher mRNA levels for 11 of the 16 examined genes at 3 than at 8 °C, and for one gene (retinol-binding protein 1), mRNA levels were higher in the presence than in the absence of the predator. Moreover, we found interaction effects between temperature and predator presence for two genes that code for serotonin and glucocorticoid receptors.
Our results suggest that piscivorous fish elicit primary stress responses in juvenile salmonids and that some of these responses may be temperature dependent. In addition, this study emphasizes the strong temperature dependence of primary stress responses in poikilotherms, with possible implications for a warming climate.
Most recent research and monitoring of under-water “soundscapes” has focused on marine systems in open water conditions. Here we present the first long-term assessment of the diel and seasonal ...patterns of a fresh-water aquatic soundscape under-ice cover. Acoustic data recorded in Yellowknife Bay, Great Slave Lake in Canada's Northwest Territories, measured the under-ice soundscape near an ice road and airport. From December to late January, the soundscape consisted of geophony from ice cracking and anthrophony from snowmobiles, aircraft, and road vehicles. In late January, burbot spawning calls began and added a localized biophony source to the soundscape that increased the total sound pressure level due to an increase in sound levels in the 10–425Hz frequency band. The median 1min root-mean-square sound pressure level (rms SPL) in the period without burbot biophony was 90.3dB re 1μPa. The measured hourly rms SPL was negatively correlated with air temperature in the 200–800Hz band but positively correlated with average hourly wind speed in the 800–8000Hz band. The nightly mean rms SPL was 88dB re 1μPa and increased to 96dB re 1μPa in late afternoon. This diel cycle had a strong positive correlation with the number of minutes per hour where ice-road vehicles were detected. Further work is recommended to quantify the soundscape in deep-water areas of large lakes and to include particle motion. Such information will enable the assessment of cumulative impacts of anthrophony and geophony on aquatic biota.
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.
Sexual dimorphic characteristics arise in response to differing selective pressures on the sexes and can be used to attract mates or signal reproductive readiness. How sexual dimorphism is expressed ...where visual cues may be of limited use is an underexplored aspect of reproductive ecology. The burbot (Lota lota (L., 1758)) is a common boreal fish that is not overtly sexually dimorphic. It spawns mid-winter in a light-limited under-ice environment. We examined a variety of morphological and reproductive characteristics in burbot from a northern lake over one full year to assess both seasonal and sex-based variation. Spawning occurred under ice in early February. Seasonal variation was more pronounced in females for many of the traits examined. Growth, fin lengths, swim bladder mass, and liver lipid concentration did not differ between the sexes. Male burbot had significantly higher body condition, larger gas glands, and smaller livers. Males also had significantly larger gonads than females, unusual for boreal fishes. The high gonadal investment of male burbot suggests that sperm competition may be intense in this species. This study demonstrates that sexual dimorphism can be subtle and is present in a seemingly monomorphic species—the burbot.
We coupled bioenergetics modeling with bottom trawl survey results to evaluate the capacity of piscivorous fish in eastern Lake Erie to exert predatory control of the invading population of round ...goby Neogobius melanostomus. In the offshore (>20 m deep) waters of eastern Lake Erie, burbot Lota lota is a native top predator, feeding on a suite of prey fishes. The round goby invaded eastern Lake Erie during the late 1990s, and round goby population size increased dramatically during 1999-2004. According to annual bottom trawl survey results, round goby abundance in offshore waters peaked in 2004, but then declined during 2004-2008. Coincidentally, round goby became an important component of burbot diet beginning in 2003. Using bottom trawling and gill netting, we estimated adult burbot abundance and age structure in eastern Lake Erie during 2007. Diet composition and energy density of eastern Lake Erie burbot were also determined during 2007. This information, along with estimates of burbot growth, burbot mortality, burbot water temperature regime, and energy densities of prey fish from the literature, were incorporated into a bioenergetics model application to estimate annual consumption of round goby by the adult burbot population. Results indicated that the adult burbot population in eastern Lake Erie annually consumed 1,361 metric tons of round goby. Based on the results of bottom trawling, we estimated the biomass of yearling and older round goby in offshore waters eastern Lake Erie during 2007-2008 to be 2,232 metric tons. Thus, the adult burbot population was feeding on round goby at an annual rate equal to 61% of the estimated round goby standing stock. We concluded that the burbot population had high potential to exert predatory control on round goby in offshore waters of eastern Lake Erie.
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