Cyclopterus Research Articles

Using a length-weight relationship based on wild lumpfish (Cyclopterus lumpus L.) for estimation of body condition of lumpfish in salmon cages.

The use of lumpfish (Cyclopterus lumpus L.) as cleaner fish in Atlantic salmon aquaculture has emerged as a promising solution to combat the issue of sea lice infestation, as they have proven effective under the right conditions. The aquaculture industry, however, is facing challenges in ensuring the welfare and survival of lumpfish in salmon cages. Part of the welfare monitoring of lumpfish is the estimation of body condition. Previous research on standard length-weight relationships for lumpfish has primarily relied on the growth patterns of lumpfish in salmon cages, which might not align with the natural growth patterns of the fish. In this study, we argue for another perspective: using the standard weight of wild lumpfish to estimate the body condition of lumpfish in salmon cages. We assert that this approach aligns more closely with the natural growth pattern of the fish and may offer a more accurate representation of their condition. Our findings show significant differences in growth patterns between wild lumpfish, which show positive allometric growth, and those in salmon cages, which show slightly negative allometric growth. The findings underscore the importance of using appropriate length-weight relationships for lumpfish in aquaculture to ensure an accurate assessment of their body condition.

Long-distance migrations, population mixing, and growth rate of lumpfish (Cyclopterus lumpus) revealed from tag-recaptures.

We reveal that lumpfish (Cyclopterus lumpus) frequently migrate over long distances between their summer feeding area in the open ocean and their spring spawning sites in coastal areas, through applying tag-recapture methodology. A total of 2750 C. lumpus were tagged in the Irminger Sea around Iceland and in the Norwegian Sea over 6 years, of which 17 C. lumpus were recaptured. Interestingly, four individuals were recaptured more than 1000 km distant from where they were tagged. C. lumpus tagged in the Irminger Sea and north of Iceland were recaptured around Iceland, whereas none of the fish tagged in other areas of the Norwegian Sea were recaptured in Iceland. This difference in recapture rate from different areas suggests that a higher proportion of C. lumpus from the Irminger Sea and north of Iceland spawns around Iceland in comparison with C. lumpus in other areas. Two fish tagged east of Iceland were recaptured on the coast of Denmark, with one fish having a displacement distance of 1612 km. The recapture of these two fish in Denmark demonstrates that part of the C. lumpus population spawning in Denmark utilizes the Norwegian Sea as a major feeding area and that the Norwegian Sea is a common feeding area for several distinct populations of C. lumpus. The growth rate of tagged fish varied from 1.2 to 11.1 cm year-1, indicating that males that are >20 cm and females that are >25 cm during the summer are capable of sufficient growth to achieve a suitable size for spawning (≥25 and ≥35 cm for males and females, respectively) the following spring.

Reproductive performance of lumpfish (Cyclopterus lumpus, L. 1758) females: Effects of integrated photoperiod and temperature manipulations on sexual maturation and spawning.

A successful control of sexual maturation is crucial for year-round production of lumpfish juveniles destined as cleaner fish in Atlantic salmon aquaculture. This study investigated the combined effects of photoperiod and temperature manipulations on sexual maturation and spawning in lumpfish females. Lumpfish juveniles were exposed to simulated natural and nine-month compressed annual photoperiods, with subsequent temperature elevation. Body weight (BW), condition factor (K), gonadosomatic index (GSI), ovarian development, plasma levels of 17β-estradiol (E2), testosterone (T) and 11-ketotestosterone (11-KT), and spawning were assessed. Compressing the natural photoperiod caused a clear increase and decrease in GSI, T, 11-KT and E2 towards and during the spawning period. Before the temperature elevation, GSI, T, 11-KT, E2 and ovarian development were advanced in the compressed photoperiod. After the temperature elevation, GSI, T, 11-KT and E2 fluctuated more in the compressed photoperiod, while in the natural photoperiod, E2 declined, and GSI, T and 11-KT increased. Spawning was advanced by 1 month in the compressed photoperiod compared to the natural photoperiod. Temperature elevation led to higher levels, earlier peaks and declines of T, 11-KT or E2 in both photoperiods, and advanced spawning by 1.5 months in the compressed photoperiod compared to the natural photoperiod. Temperature elevation also led to increased ovulation recruitment and increased cumulative weight of spawned eggs in the natural photoperiod. Compressing the natural photoperiod and elevating temperature can thus advance sexual maturation and spawning in lumpfish females. Due to the lower amounts of spawned egg weights in the high temperature compressed photoperiod, further studies on effects of photoperiod and timing of temperature manipulations on spawning, fecundity and egg quality could optimize the photothermal manipulations on lumpfish broodstock.

The thermal dependent biology of cultured lumpfish (Cyclopterus lumpus Linnaeus 1758): Differences due to temperatures during early life and how tolerance is measured

The use of lumpfish as a “cleaner fish” in Atlantic salmon aquaculture is increasing. However, during the summer months, there have been large-scale mortalities of lumpfish at some North Atlantic salmon sea-cage sites. There is evidence that manipulating temperatures during early life can improve the thermal tolerance of fishes. Thus, we reared lumpfish embryos (eggs), larvae and juveniles under different temperature regimes, and measured their metabolic physiology and upper thermal limits, with the goal of better understanding their physiology and mitigating the effects of high summer water temperatures on their welfare. The specific incubation (egg) / rearing temperature combinations were 6 °C / 9 °C (normal production temperatures), 8.5 °C / 9 °C, 6–11 °C / 9 °C, 8.5 °C / 9–11 °C and 6–11 °C / 9–11 °C; with a range of temperatures indicating that fish were exposed to stochastic temperature changes.Hatching success was 61 % in the control (6 °C) group, as compared to ~47 % and 26.5 % in the groups exposed to 8.5 °C and the stochastic temperature regime (6–11 °C), respectively. Groups exposed to stochastic incubation and rearing temperatures also had the lowest survival rate (33.7 %) as opposed to those incubated and reared at constant temperatures (66.1 and 50.7 %) when unexpectedly exposed to high, and variable, ambient water temperatures that were experienced for roughly 7 weeks during rearing (due to abnormal water temperatures in the bay supplying our aquaculture facility). Interestingly, the critical thermal maximum (CTMax), incremental temperature maximum (ITMax) and metabolic capacity (i.e., aerobic scope) of 30-40 g lumpfish did not differ between the groups, and the first two parameters on average were 22.85 ± 0.12 °C and 20.63 ± 0.02 °C, respectively.

Heterogeneous Weight Development of Lumpfish (Cyclopterus lumpus) Used as Cleaner Fish in Atlantic Salmon (Salmo salar) Farming

Lumpfish (Cyclopterus lumpus) are used as cleaner fish in Atlantic salmon (Salmo salar) aquaculture as one of multiple control measures against salmon lice (Lepeophtheirus salmonis). Numerous studies have documented weight as an important factor for characterising the cleaning efficacy of individual lumpfish. Hence, the efficacy of lumpfish in fish farms depends on the size at stocking and the weight development over time. Here, we aimed to quantify how weight developed over time for lumpfish deployed in salmon farming sea cages in Norway through modelling the daily growth rate. We found that the coefficient of variation for lumpfish weight increased over time, implying that the standard deviation increased more than the expected weight. The data thus showed heterogeneous growth for lumpfish in salmon farming cages, where some individuals exhibited no apparent growth, and others significant proliferation. We found that the daily growth rate was best described as bell-shaped functions of weight and temperature, consistent with a sigmoid-shaped growth curve and an optimal temperature around 10 °C. These results allow for more realistic modelling of the efficacy of lumpfish in controlling salmon lice in fish farms, as one can combine estimates of weight-dependent cleaning efficacy with weight development over time.

The gifts of multiple perspectives: a Two-Eyed Seeing approach to Gumegwsis (Cyclopterus lumpus) ecology in inner Mawipoqtapei (Chaleur Bay), Eastern Canada

The gifts of multiple perspectives: a Two-Eyed Seeing approach to Gumegwsis (Cyclopterus lumpus) ecology in inner Mawipoqtapei (Chaleur Bay), Eastern Canada

Lumpfish, Cyclopterus lumpus, distribution in the Gulf of Maine, USA: observations from fisheries independent and dependent catch data.

The Gulf of Maine (GoM) is one of the fastest-warming parts of the world's oceans. Some species' distributional shifts have already been documented, especially for commercially-important species. Less is known about species that are not currently exploited but may become so in the future. As a case study into these issues, we focus on lumpfish (Cyclopterus lumpus) because of the recognized and timely need to understand wild lumpfish population dynamics to support sustainable fisheries and aquaculture developments. Using occurrence data from five different fisheries-dependent and independent surveys, we examined lumpfish distribution over time in the GoM. We found that lumpfish presence was more likely in Fall and correlated with deeper waters and colder bottom temperatures. Since 1980, lumpfish presence has increased over time and shifted north. Given a limited set of data, these findings should be interpreted with caution as additional work is needed to assess if the actual distribution of lumpfish is changing. Nevertheless, our work provides preliminary information for resource managers to ensure that lumpfish are harvested sustainably for use in emergent lumpfish aquaculture facilities.

Industrial Buyers’ Food Neophobia – A Barrier to Market Entry? A Case Study of Introducing Lumpfish to South Korea and Vietnam

The need to find sustainable food sources to feed the growing population makes the utilization of all available food resources especially important. But introducing new food is challenging and often fails. In the consumer behavior literature, food neophobia (FN), the unwillingness to try new food, has been identified as a crucial factor in understanding the adoption of new food products. However, limited research can be found on the role of FN in industrial buyers’ choice of new food products. Industrial buyers are important gatekeepers for the introduction of new food products as they decide what is offered to the consumers and may stop any market entry long before a new food product reaches the consumers’ attention. Thus, the understanding of the potential FN in industrial buying behavior, in different markets, is important to succeed with the introduction of new food products. In this study, we have explored FN as a potential barrier to the adoption of a new seafood product, farmed lumpfish (Cyclopterus lumpus), by industrial buyers in South Korea and Vietnam. The results revealed differences between the two countries’ industrial buyers, with South Koreans demonstrating more FN than the Vietnamese. This contradicts with the consumer research showing that FN decreases with increased income, education, and urbanization.

Tolerance of juvenile lumpfish (Cyclopterus Lumpus) to high rearing densities

AbstractLumpfish (Cyclopterus lumpus) are raised as cleaner fish for controlling sea lice. Intensive rearing is complicated by fin nipping that occurs between juvenile conspecifics. Lumpfish density‐dependent interactions are not well understood; therefore, the effects of rearing density for different fish size classes warranted evaluation. Two size classes (2‐ and 13‐g) of juvenile lumpfish were stocked at four different rearing densities (40, 60, 70, and 90 g/L) with growth, survival, and fish aggression assessed over 8 weeks. Mean weight gain and specific growth rates ranged from 170% to 307% and 1.77% to 2.50%, respectively, depending on density treatments, for the 2‐g fish, and from 286% to 471% and 2.42% to 3.10% for the 13‐g fish. Growth was negatively correlated with density, with faster growth linked to lower densities. No mortality occurred in any treatment and significant fish aggression only occurred among the larger lumpfish in the higher rearing densities. Based on these findings, growth of 2‐g lumpfish can be increased if reared at 40 g/L or slowed at 70 g/L without impacting aggression. For grow out of 13‐g fish to ~70 g with minimal aggression, a 40 g/L rearing density is recommended for faster growth and 60 g/L for slower growth.

Understanding the Causes of Lumpfish (Cyclopterus lumpus) Mortality in Norwegian Hatcheries: Challenges and Opportunities

Understanding the Causes of Lumpfish (Cyclopterus lumpus) Mortality in Norwegian Hatcheries: Challenges and Opportunities

Inflammatory responses in Atlantic lumpfish (Cyclopterus lumpus L.) after intraperitoneal injection of a vaccine against Aeromonas salmonicida and Vibrio salmonicida at different water temperatures.

Studying inflammatory responses induced by vaccination can contribute to a more detailed understanding of underlying immune mechanisms in lumpfish (Cyclopterus lumpus). Tissue samples from lumpfish intraperitoneally immunized with a divalent oil-adjuvanted vaccine (Aeromonas salmonicida and Vibrio salmonicida) at water temperatures of 5, 10, and 15°C were collected at 630 day degrees and 18 weeks post injection. The relative amount of secretory and membrane-bound immunoglobulin M (IgM) gene transcripts in the head kidney was determined by qPCR. Vaccine-induced inflammatory lesions were assessed on histological sections of abdominal pancreatic/intestinal tissue from vaccinated fish in all three temperature groups. Inflammatory cells forming dense aggregations in lesions showed proliferative activity, many of which were identified as eosinophilic-granulocyte-like cells. IgM+ cells were scattered in inflammatory tissue dominated by connective tissue, showing no difference in numbers between lesions from fish vaccinated at 5, 10, and 15°C. Relative gene expression analysis of secretory and membrane-bound IgM revealed low overall expression in the head kidney of vaccinated fish at both 630 day-degrees and 18 weeks post injection. The results of this study indicate that the vaccine stimulated prolonged local inflammatory responses at the injection site, which were not influenced by temperature.

Analyses of the Mx family members in lumpfish: Molecular characterization, phylogeny, and gene expression analyses

Members of the myxovirus resistance (Mx) protein family play an essential role in antiviral immunity. They are Dynamin-like GTPases, induced by interferons. In the current study, we have characterized two predicted MX genes (MX1 and MX2) from lumpfish (Cyclopterus lumpus L.), having 12 and 13 exons, respectively. Mx2 has two isoforms (Mx2-X1 and Mx2-X2) which differ in exon 1. The lumpfish Mx proteins contain an N-terminal Dynamin-like GTPase domain, the middle domain (MD) and GTPase effector domain (GED) characteristic for Mx proteins. Phylogenetic analyses grouped all the lumpfish Mx sequences in group 1, and synteny analyses showed that both genes were localized at chromosome 5 in proximity to the genes Tohc7, Atxn7 and Psmd6. In vitro stimulation experiment showed that both MX1 and MX2-X2 were highly upregulated upon exposure to poly(I:C), but not bacteria, 24 h post exposure, indicating their role in antiviral immunity.

The effects of light, rearing density, and fish size in culturing juvenile Lumpfish

AbstractObjectiveThere is an impetus for increasing Lumpfish Cyclopterus lumpus hatchery production and rearing efficiency due to the high demand for their usefulness as cleaner fish in salmonid ocean farming. One production bottleneck is the loss of juvenile fish due to aggressive behaviors, including cannibalism. Understanding which factors exacerbate Lumpfish aggression and providing mitigation guidelines to aquaculturists are warranted.MethodsTwo experiments were conducted for an 8‐week period in 2022 in 3‐L aquaria with different juvenile size‐classes (4 and 11 g) subjected to three rearing densities (40, 65, and 90 g/L) under different photoperiod regimes (12 h light : 12 h dark [113 lx]; 24 h light : 0 h dark [21 lx]; and 24 h light : 0 h dark [302 lx]), resulting in nine experimental treatments. Survival, growth, and aggression (occurrence and severity of caudal fin nipping) were evaluated.ResultFor 4‐g Lumpfish, light and density significantly affected growth (weight gain and specific growth rate), while an interaction between light and density significantly affected the occurrence of caudal fin nipping but not the degree of fin nipping or survival. None of the tested variables significantly affected 11‐g fish. Generally, a trend toward increased caudal fin nipping occurred in smaller fish (~45% occurrence in 4‐g fish vs. ~20% in 11‐g fish), indicating that cannibalism may be even greater when Lumpfish are smaller than 4 g but abates as the fish grow.ConclusionOur findings indicate that manipulation of lighting at rearing densities of up to 90 g/L can be used to control growth rates in small Lumpfish, often without resulting in increased fish aggression. For small (~4‐g) Lumpfish, constant low light intensity in combination with a low (40‐g/L) rearing density is recommended for reducing growth and caudal fin nipping. However, as Lumpfish grow, these variables are less effective at manipulating fish growth.

Role of cold shock proteins B and D in Aeromonas salmonicida subsp. salmonicida physiology and virulence in lumpfish (Cyclopterus lumpus).

Cold shock proteins (Csp) are pivotal nucleic acid binding proteins known for their crucial roles in the physiology and virulence of various bacterial pathogens affecting plant, insect, and mammalian hosts. However, their significance in bacterial pathogens of teleost fish remains unexplored. Aeromonas salmonicida subsp. salmonicida (hereafter A. salmonicida) is a psychrotrophic pathogen and the causative agent of furunculosis in marine and freshwater fish. Four csp genes (cspB, cspD, cspA, and cspC) have been identified in the genome of A. salmonicida J223 (wild type). Here, we evaluated the role of DNA binding proteins, CspB and CspD, in A. salmonicida physiology and virulence in lumpfish (Cyclopterus lumpus). A. salmonicida ΔcspB, ΔcspD, and the double ΔcspBΔcspD mutants were constructed and characterized. A. salmonicida ΔcspB and ΔcspBΔcspD mutants showed a faster growth at 28°C, and reduced virulence in lumpfish. A. salmonicida ΔcspD showed a slower growth at 28°C, biofilm formation, lower survival in low temperatures and freezing conditions (-20°C, 0°C, and 4°C), deficient in lipopolysaccharide synthesis, and low virulence in lumpfish. Additionally, ΔcspBΔcspD mutants showed less survival in the presence of bile compared to the wild type. Transcriptome analysis revealed that 200, 37, and 921 genes were differentially expressed in ΔcspB, ΔcspD, and ΔcspBΔcspD, respectively. In ΔcspB and ΔcspBΔcspD virulence genes in the chromosome and virulence plasmid were downregulated. Our analysis indicates that CspB and CspD mostly act as a transcriptional activator, influencing cell division (e.g., treB), virulence factors (e.g., aexT), and ultimately virulence.

Correction to: trans-Atlantic genomic differentiation and parallel environmental and allelic variation in Lumpfish (Cyclopterus lumpus)

Correction to: trans-Atlantic genomic differentiation and parallel environmental and allelic variation in Lumpfish (<i>Cyclopterus lumpus</i>)

More sustainable use of aquaculture cleaner fish: collagen-rich protein hydrolysates from lumpfish (Cyclopterus lumpus) – effects of biomass, pretreatment, and enzyme choice

More sustainable use of aquaculture cleaner fish: collagen-rich protein hydrolysates from lumpfish (Cyclopterus lumpus) – effects of biomass, pretreatment, and enzyme choice

Systematic analysis of ocular features and responses of cultured spotted wolffish (Anarhichas minor).

A better understanding of unique anatomical and functional features of the visual systems of teleost fish could provide key knowledge on how these systems influence the health and survival of these animals in both wild and culture environments. We took a systematic approach to assess some of the visual systems of spotted wolffish (Anarhichas minor), a species of increasing importance in North Atlantic aquaculture initiatives. The lumpfish (Cyclopterus lumpus) was included in these studies in a comparative manner to provide reference. Histology, light and electron microscopy were used to study the spatial distribution and occurrence of cone photoreceptor cells and the nature of the retinal tissues, while immunohistochemistry was used to explore the expression patterns of two photoreceptor markers, XAP-1 and XAP-2, in both species. A marine bacterial infection paradigm in lumpfish was used to assess how host-pathogen responses might impact the expression of these photoreceptor markers in these animals. We define a basic photoreceptor mosaic and present an ultrastructural to macroscopic geographical configuration of the retinal pigment tissues in both animals. Photoreceptor markers XAP-1 and XAP-2 have novel distribution patterns in spotted wolffish and lumpfish retinas, and exogenous pathogenic influences can affect the normal expression pattern of XAP-1 in lumpfish. Live tank-side ophthalmoscopy and spectral domain optical coherence tomography (SD-OCT) revealed that normal cultured spotted wolffish display novel variations in the shape of the retinal tissue. These two complementary imaging findings suggest that spotted wolffish harbour unique ocular features not yet described in marine teleosts and that visual function might involve specific retinal tissue shape dynamics in these animals. Finally, extensive endogenous biofluorescence is present in the retinal tissues of both animals, which raises questions about how these animals might use retinal tissue in novel ways for visual perception and/or communication. This work advances fundamental knowledge on the visual systems of two economically important but now threatened North Atlantic teleosts and provides a basic foundation for further research on the visual systems of these animals in health versus disease settings. This work could also be useful for understanding and optimizing the health and welfare of lumpfish and spotted wolffish in aquaculture towards a one health or integrative perspective.

Trans-Atlantic genomic differentiation and parallel environmental and allelic variation in Lumpfish (Cyclopterus lumpus)

Abstract In marine species with large populations and high dispersal potential, large-scale genetic differences and clinal trends in allele frequency can provide insight into the evolutionary processes that shape diversity. Lumpfish, Cyclopterus lumpus, is found throughout the North Atlantic and has traditionally been harvested for roe and more recently used as a cleaner fish in salmon aquaculture. We used a 70 K SNP array to evaluate trans-Atlantic differentiation, genetic structuring, and clinal variation across the North Atlantic. Basin-scale structuring between the Northeast and Northwest Atlantic was significant, with enrichment for loci associated with developmental/mitochondrial function. We identified a putative structural variant on chromosome 2, likely contributing to differentiation between Northeast and Northwest Atlantic Lumpfish, and consistent with post-glacial trans-Atlantic secondary contact. Redundancy analysis identified climate associations both in the Northeast (N = 1269 loci) and Northwest (N = 1637 loci), with 103 shared loci between them. Clinal patterns in allele frequencies were observed in some loci (15%—Northwest and 5%—Northeast) of which 708 loci were shared and involved with growth, developmental processes, and locomotion. The combined evidence of trans-Atlantic differentiation, environmental associations, and clinal loci, suggests that both regional and large-scale potentially-adaptive population structuring is present across the North Atlantic.

Draft genome sequences of 13 Tenacibaculum maritimum isolates from farmed Norwegian Cyclopterus lumpus (lumpfish) and Scophthalmus maximus (turbot).

Thirteen bacterial isolates of Tenacibaculum maritimum were sequenced and assembled. The strains were isolated from four disease outbreaks in farmed marine fish in Norway. Eight isolates were from Cyclopterus lumpus (lumpfish), and five were from Scophthalmus maximus (turbot). Overall, sequence similarity did not correlate with host species or geographic location.

Utilization of Lumpfish (Cyclopterus lumpus) Skin as a Source for Gelatine Extraction Using Acid Hydrolysis.

Lumpfish (Cyclopterus lumpus) is an underutilized marine resource that is currently only being exploited for roe. Lumpfish skin was pre-treated with alkali (0.1M NaOH) and acid (0.1M HCl) at a skin to chemical ratio of 1:10 for 24 h at 5 °C to remove non-collagenous proteins and minerals. The pre-treated skin was washed, and gelatine was extracted with 0.1M of acetic acid at three different ratios (1:5, 1:10, and 1:15), time (12,18, and 24 h), and temperature combinations (12, 28, and 24 °C). The highest total extraction yield (>40%) was obtained with combinations of extraction ratios of 1:15 and 1:10 with a longer time (24 h) and higher temperature (18-24 °C). The highest gelatine content was obtained with an extraction period of 24 h and ratio of 1:10 (>80%). SDS-PAGE analysis confirmed the presence of type-I collagen. A rheological evaluation indicated melting and gelling temperatures, gel strength, and viscosity properties comparable to existing cold-water gelatine sources.