Burbot, Lota lota are a candidate species for commercial aquaculture because of their palatability and optimal growth at temperatures similar to those used in freshwater trout aquaculture. However, ...data on burbot environmental tolerances and requirements are sparse, especially with reference to water quality parameters relevant to aquaculture, such as un-ionized ammonia (UIA) concentration. We used a two-phased approach to evaluate the effects of un-ionized ammonia on the growth and survival of burbot. First, we measured the acute toxicity of ammonia to juvenile burbot (mean SL: 144 ± 6 mm; mean wet weight: 27.3 ± 3.4 g) and calculated a 96-h LC50 of 0.58 mg·L−1 UIA. We then measured the 60-d growth, food consumption rate, and performance of burbot (mean initial SL: 190 ± 6.9 mm; mean initial weight: 67.0 ± 4.5 g) reared in 0.00, 0.03, 0.06, 0.12, or 0.19 mg·L−1 UIA using a 20-tank flow-through system under optimal temperature (14.7 °C) and dissolved oxygen (DO >80% saturation) conditions. Elevated ammonia concentration significantly reduced daily food consumption and subsequent growth. Fish exposed to 0.03 and 0.06 mg·L−1 UIA showed temporal acclimation to UIA, achieving food consumption and growth rates on par with control fish after 30 days of exposure. The estimated effective UIA concentrations for 10 and 20% reductions in growth (EC10 and EC20) based on our data are: EC10 = 0.03 ± 0.006 mg·L−1 and EC20 = 0.050 ± 0.004 mg·L−1. We recommend rearing burbot under conditions that keep UIA levels ≤0.03 mg·L−1 based on our finding that above 0.03 mg·L−1 cause measurable reductions in growth rate.
•The acute toxicity (96-h LC50) of un-ionized ammonia to juvenile burbot was measured.•After determining the acute tolerance of ammonia, we subsequently measured sub-lethal growth and survival to elevated ammonia in a chronic exposure (60-days) study.•We recommend un-ionized ammonia levels be held under 0.03 mg·L−1 to avoid reduced growth in aquaculture facilities.
The burbot, Lota lota, is being explored as a novel aquaculture species in North America due to its palatability and potential to be grown in areas that currently support rainbow trout, Oncorhynchus ...mykiss culture. Dissolved oxygen (DO) concentration is a primary limiting factor in fish survival and growth, with tolerance varying among species. We exposed juvenile burbot (19.5 ± 2.2 g) to five dissolved oxygen concentrations (5.0, 5.8, 6.6, 7.4, and 8.3 (control) mg·L −1) for 9 weeks at 15 °C. Size variability was high in all treatments, and food consumption, and growth rates did not differ among DO levels, although fish at 8.3 mg·L−1 grew ca. 29% larger than those at 5.0 mg·L−1. We also measured short-term hypoxia tolerance and resting routine oxygen consumption rates (MO2) of burbot that had been chronically acclimated to the same DO concentrations. Burbot acclimated to 8.3 mg·L−1 lost equilibrium (LOEcrit) at a significantly higher concentration (1.85 ± 0.33 mg·L −1) than that of the 7.4 and 6.6 mg·L −1 acclimated fish (1.50 ± 0.37 and 1.49 ± 0.27; respectively), while all other groups were intermediate (1.67 ± 0.28). The MO2s were not statistically distinguishable among acclimation groups (p-value = 0.25), but MO2 trended lower with decreasing DO concentrations. In summary, juvenile burbot are tolerant to DO concentrations down to 5.0 mg·L −1. We recommend rearing burbot at DO concentrations >7.0 mg·L −1 to optimize growth, especially with the presence of multiple stressors.
•Juvenile burbot showed no significant growth reduction down to 5.0 mg·L−1 dissolved oxygen.•Large weight variation was measured in all tanks and treatment groups, possibly indicating a non-treatment effect.•Mean loss of equilibrium dissolved oxygen concentration (LOEcrit) for all groups combined was 1.58 mg·L−1.•Burbot displayed decreasing mean oxygen consumption rates with falling dissolved oxygen concentrations.
The feasibility of triploid induction for burbot (Lota lota) was determined following a series of hydrostatic (pressure) and thermal (heat) shock treatments. Hydrostatic shock treatments were ...designed to test a range of variables including 1) duration of shock; 2) timing of shock (post-fertilization); and 3) shock pressure. Shock times post-fertilization and shock duration were varied by degree minutes (°C minutes). A hydrostatic shock of 8,500psi at 180 °C minutes post-fertilization for 10 °C minutes yielded the highest percent triploid induction (100%) and survival (95%) relative to the controls. Duration of pressure-shock longer than 10 °C min at 8,500psi and higher, resulted in 100% pre-hatch mortality. A reduced shock pressure (7,500psi) resulted in a high percent triploidy (100%), but pre-hatch larval survival was 65.5% at a shock duration of 30 °C minutes. Thermal shock treatments included: duration of shock, timing of shock, and shock temperature. Triploid induction and survival were greatest following a thermal shock of 16 °C at 120 °C minutes post-fertilization for 500 °C minutes. This resulted in 96.6% triploidy and 57.4% survival relative to control groups. Shock temperatures above 16 °C generally resulted in a higher percent triploid induction but lower survival. Results presented here confirm that triploid induction in burbot is possible. Further work is needed to confirm scale up potential, survival dynamics, sterility of triploid burbot, and changes in growth performance. Production of sterile burbot may increase opportunities for culturing burbot in areas where escapement may be a concern or when growth is inhibited due to reproductive maturation.
•Heat shock of 16 °C at 120 °C minutes post-fertilization for 500 °C minutes yielded 96.6% triploidy relative to control groups.•Hydrostatic shock of 8,500psi at 180 °C minutes post-fertilization for 10 °C minutes produced 100% triploid induction.•Triploid burbot production may allow for culture in areas were escapement is a concern or increase growth potential.
The aquaculture industry needs to increase the diversity of fish species to meet consumers' escalating demands. Burbot (Lota maculosa) has emerged as a promising candidate for such diversification. ...Nonetheless, a dearth of knowledge exists concerning their sensory characteristics and overall consumer acceptance. This study sought to investigate these crucial aspects, which are instrumental in assessing the market potential of this fish species. A consumer survey was conducted in Idaho from March through July 2017 to initially evaluate burbot's consumer acceptance and market potential. Results showed that over 96% of consumers liked the texture of burbot, 92% liked the flavor of the burbot, and 90% would try burbot again. Significant reasons for consumers' willingness to eat burbot included cooking preparation, tasty, mild flavor, excellent texture, and excellent flavor. Results from this indicate that burbot is a promising food fish candidate for commercialization. Based on these results, a follow-up panelists survey and sensory analysis were conducted in April 2019 to further investigate consumer acceptance and sensory properties of burbot when compared to other prominent aquaculture species (trout and tilapia). The three species exhibited different sensory profiles; however, burbot was ranked significantly higher for aroma, flavor, and taste. Conversely, panelists found tilapia and trout to be significantly (P < 0.05) firmer than burbot for firmness. The results from the sensory testing showed that 87% and 81% of panelists preferred burbot to tilapia and trout, respectively, and 79% would be willing to try this as a new species on the market. The distinct profiles of burbot indicate that this fish species would be highly marketable and if available would contribute to the diversification of U.S. commercial aquaculture by offering a delicate white fillet option to salmonids.
•Consumers liked the texture and flavor of the burbot and expressed keen interest in consuming the burbot again as a new option in the market.•Burbot was preferred over trout and tilapia in terms of taste, aroma, flavor, and texture.•Burbot could be a highly marketable species and can help contribute to the diversification of U.S. commercial aquaculture by providing a delicate white fillet alternative to salmonids.
Intensive commercial production of burbot fingerlings will depend on consistent supply of eggs and larvae at multiple times during the year; however, no information on out-of-season spawning of ...burbot exists. The current study was designed to shift sexual maturation of burbot broodstock by six months from the natural spawning season through temperature and photoperiod manipulation. Results demonstrated that out-of-season spawning of burbot was successful. Broodstock, egg quality, and larval condition data were compared between out-of-season and in-season groups. For both production regimes, broodstock were sampled for condition factor and egg production, and embryos were monitored for development, viability, and survival. Larvae were reared to 35 days post hatch (dph) for growth and survival comparison. There was no significant difference in pre-spawn condition factor between in-season and out-of-season males or females. Post-spawn condition factor for out-of-season females was not statistically different from in-season females, 0.83 (±0.06) and 0.66 (±0.07) respectively. However, post-spawn condition factor for out-of-season male broodstock was significantly higher, 0.82 (±0.04), than in-season fish, 0.64 (±0.02). Eggs produced relative to weight of pre-spawn female did not differ significantly between in-season and out-of-season production, 328.5 (±22.95) and 213 (±38.04) eggs/g, respectively. Fertilization did not differ significantly between treatments, averaging 90% for both in and out-of-season production. Egg survival was higher, 61.18% (±9.3), in the final week of incubation for out-of-season groups compare to eggs from in-season broodstock, 20.59% (±10.6). However, no difference in larval growth or survival was observed out to the 35dph termination point. Overall, egg quality and larval survival was not negatively impacted for broodstock spawned out-of-season. This is the first report demonstrating that burbot eggs can be produced outside the natural spawning season by altering photoperiod and temperature. As commercial production of this species develops, this will be an important tool to mitigate the risk of relying on a single annual spawning season and can ensure a consistent supply of burbot fingerlings throughout the year.
•Sexual maturation and spawning of burbot was shifted six months from natural spawning season with photothermal manipulation•Egg and larval quality did not differ between out of season and natural in-season broodstock•As commercial production of burbot develops this will be an important tool to alleviate risks of an annual spawning season
Background In fish with external fertilization, two main start-up mechanisms of the path that blocks or activates the spermatozoan motility apparatus are known. The main factor managing the path is ...osmolality or potassium ion. In burbot from the European and North American population, contradictory findings regarding the factors influencing the onset of spermatozoa motility were reported. The objective of the current study was to determine the effect of potassium and osmolality on the spermatozoa activation of European burbot, Lota lota (Actinopterygii, Gadiformes, Lotidae). Moreover, the influence of pH, as well as sodium ion concentrations on spermatozoa motility was investigated. Seven parameters characterising motility were traced by means of computer-assisted sperm analysis (CASA). Principal findings The spermatozoa of European burbot are K.sup.+ ion-sensitive. A 6-mM KCl solution significantly decreased motility, and above 12-mM (50 mOsm kg.sup.-1) totally ceased spermatozoa movement. Sucrose and Na.sup.+ solutions inhibited spermatozoa movement only at concentrations > 450-480 mOsm kg.sup.-1 . Greater differences in the percentage of motile sperm between individuals were noted in solutions containing high concentrations of chemicals triggering sperm motility. The optimum osmolality for spermatozoa motility is in the range of 100-200 mOsm kg.sup.-1 . The burbot spermatozoa were motile over a wide range of pH values with the best activation at pH 9. Conclusion It was demonstrated that the spermatozoa of European burbot are inhibited by K.sup.+ ions similarly as in North American burbot. Other electrolyte and non-electrolyte solutions inhibit spermatozoa movement only if their osmolality is greater than that of the physiological osmolality of seminal plasma. The data provided on basic knowledge of burbot spermatozoa allow to ensure appropriate conditions during artificial reproduction and scientific research.
Burbot (Lota lota maculosa) are the only true freshwater gadiforms (cod-like fish) and are a promising new species for cold water aquaculture. This “freshwater cod” produces a delicate white flesh ...fillet, the liver and roe are considered delicacies, and the skin can be manufactured into leather. Furthermore, burbot grow-out requires similar water quality parameters as trout production, and burbot have been found to be relatively refractory to most primary salmonid pathogens. Burbot could be reared at existing trout production facilities and represent a means of diversifying production in already established cold water aquaculture operations. For commercial burbot culture to succeed, optimal diet selection for grow-out must be determined. To address this, two feeding trials were conducted to evaluate the effect of different dietary formulations on the growth of juvenile and subadult burbot. Four dietary treatments at fixed rations were evaluated, Europa (commercial), Oncor (commercial), a formulated marine-like reference diet (Burbot 1; B1), and a formulated trout-like reference diet (Burbot 2; B2). Juvenile growth results indicated a difference in relative growth (RG; P < .001) and biomass gain (BG; P < .001) among the marine blend dietary treatments, with the fish fed B1 and Europa showing better growth than the Oncor and B2 diets in these cases. This is indicative of a preference for marine-type diets during the juvenile life stage of burbot. Growth results also indicate a difference in protein efficiency ratio (PER; P = .008) among the diets, with the fish fed Europa exhibiting the lowest protein utilization rate. Subadult growth results indicate no differences in RG (P = .771), SGR (P = .804), BG (P = .727) for fish fed any of the diets. Thus, it appears that the subadult burbot grow and perform equally well on trout-like formulations at this life stage. While additional studies are needed, results from this work are important and indicate general dietary preference of burbot at juvenile and grow-out stages. Such information can be used to guide feed related decisions for current or future producers interested in commercial burbot production.
•Feeding trials evaluated the effect of commercial and formulated diets on the growth of juvenile and subadult burbot.•Juvenile burbot growth performance results indicated a preference for higher protein marine-type diets at this life stage.•Subadult burbot did not show differences in overall growth performance perform equally well on trout-like formulations.
Hydropower has long been an effective form of renewable energy, but the development of the resource has negatively impacted fishes throughout the world. Formulating recovery plans to mitigate these ...effects requires a firm understanding of species‐specific provenance, life history and life stage habitat requirements. However, the importance of this information is often only recognised after a substantial population decline, when obtaining it becomes demographically challenging. We provide a case study for this scenario and present a post hoc approach to gain insight into these critical data gaps for Burbot Lota lota in the upper Kootenai River in Montana and British Columbia. The population once supported a robust tribal and recreational harvest but declined following impoundment and these fisheries have remained closed or curtailed for nearly 20 years. The reasons for the decline are unknown and actions to assist recovery have been constrained by limited information regarding natal origin, life history and habitat use. We addressed this issue using strontium isotope ratios (87Sr/86Sr) in otoliths collected over four decades in Lake Koocanusa, the reservoir on the Kootenai River above Libby Dam. Due to the geologic heterogeneity of the basin and resulting variation in water 87Sr/86Sr, the assignment probability for Burbot to their region of natal origin approached unity. Otolith 87Sr/86Sr also indicated the population was comprised of mainstem‐ and tributary‐origin forms and their relative abundance changed over time. Mainstem Burbot was most abundant during the 1970s and 2000s, whereas tributary forms dominated between these periods. We suggest ecosystem changes following impoundment contributed to this shift in life history forms and the overall decline of the population. Our findings underscore the need for additional investigations of these impacts to guide restoration efforts.
Abstract Objective The primary objective of this study was to determine how soy products affect Burbot Lota lota maculosa growth and gastric evacuation. The secondary objective was to determine the ...digestibility of common soy products in Burbot. Methods A 130‐day feed study was conducted with subadult (grow‐out stage) Burbot to evaluate performance with 25% of the dietary fish meal replaced with soybean meal or soy protein concentrate compared with a control diet formulated to resemble a salmonid diet. Additionally, diets from the feed study, along with chironomid meal (a natural forage item), were used to determine Burbot gastric evacuation rates using fish naive to soy. These diets, containing over 12% soy, were applied to fish from the same cohort of Burbot used in the initial feed study. A digestibility assessment was conducted using diets with 30% of the fish meal replaced with soybean meal, soy protein concentrate, and a fermented soybean meal. Result No differences in growth performance were observed. The gastric evacuation assessment revealed that soy protein concentrate was evacuated at a significantly higher rate than chironomid meal; however, no other differences in gastric evacuation rates among diets were detectable. Apparent digestibility of protein was significantly higher in the soybean meal, soy protein concentrate, and fermented soybean meal treatments relative to the control diet. Apparent lipid digestibility was significantly lower in the soybean meal diet relative to the control diet; however, neither diet was significantly different from the soy protein concentrate or fermented soybean meal treatments. Conclusion Soy protein is highly digestible in grow‐out‐stage Burbot, these fish can be produced to market size on diets with ≥25% of the fish meal (relative to the experimental control diet) replaced with soybean meal or soy protein concentrate with no impact on growth performance relative to a salmonid diet formulation.
Impact statement For the aquaculture industry to continue to grow in a sustainable fashion, and meet consumer demand, more sustainable alternatives to fish meal must be identified. In this article we demonstrate that grow‐out stage Burbot can be produced to market size with at least 25% of the fish meal, relative to the trout‐like control diet, replaced with soybean meal or soy protein concentrate with no impact on growth.
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