Cyclopterus Research Articles

Variability in Parental Behavior of Lumpfish Cyclopterus lumpus (Cyclopteridae) under Changing Environmental Conditions

Variability in Parental Behavior of Lumpfish Cyclopterus lumpus (Cyclopteridae) under Changing Environmental Conditions

Microplastics in Commercial Fishes and By-Catch from Selected FAO Major Fishing Areas of the Southern Baltic Sea.

According to recent world wide studies, microplastics (MPs) have been found in many fish species; however, the majority of research has focused only on the gastrointestinal tract, neglecting edible organs. This study aimed to assess the presence of microplastics in the non-edible (gills, digestive tract) and edible organs (liver) of three commercial fish species and twoby-catch species from the southern Baltic Sea. Fish (Clupea harengus, Gadus morhua, Platichthy sflesus, Taurulus baublis, Cyclopterus lumpus) were caught in 108 and 103 FAO Fishing Zones belonging to the Polish fishing zone. The abundanceof MPs ranged from 1 to 12 items per fish, with an average of 4.09 items. MPs were observed in different organs, such as the liver, gills, and digestive tract of all five tested species. MPs recognized as fibers were the most abundant. Other shapes of polymers found in fish organs were pellets and particles of larger plastic pieces. The dominant color of the MPs was blue, but there were also red, black, transparent, yellow, green, and white items found. According to dimensions, dominant MPs were between 0.1 and 0.5 mm in size. The chemical characterization of polymers accomplished by the use of Fourier Transform Infrared (FT-IR) Spectroscopy demonstrated the abundance of cellophane, polyamide, polyethylene, polypropylene, polyethylene terephthalate, polyvinyl propionate, polyacrylonitrile, and polyester.

Magnetic fields generated by submarine power cables have a negligible effect on the swimming behavior of Atlantic lumpfish (Cyclopterus lumpus) juveniles.

Submarine power cables carry electricity over long distances. Their geographic distribution, number, and areal coverage are increasing rapidly with the development of, for example, offshore wind facilities. The flow of current passing through these cables creates a magnetic field (MF) that can potentially affect marine organisms, particularly those that are magnetosensitive. The lumpfish (Cyclopterus lumpus) is a migratory species that is widely distributed in the North Atlantic Ocean and Barents Sea. It migrates between coastal spawning grounds and pelagic offshore feeding areas. We tested whether lumpfish respond to MFs of the same intensity as those emitted by high voltage direct current (HVDC) submarine power cables. Laboratory experiments were conducted by placing juvenile lumpfish in an artificial MF gradient generated by a Helmholtz coil system. The intensity of the artificial MF used (230 µT) corresponded to the field at 1 m from a high-power submarine cable. The fish were filmed for 30 min with the coil either on or off. Swimming speeds, and presence in the different parts of a raceway, were extracted from the videos and analyzed. Juvenile lumpfish activity, defined as the time that the fish spent swimming relative to stationary pauses (attached to the substrate), and the distance travelled, were unaffected by exposure to the artificial MF. The swimming speed of juvenile lumpfish was reduced (by 16%) when the coil was on indicating that the fish could either sense the MF or the induced electric field created by the movement of the fish through the magnetic field. However, it seems unlikely that a 16% decrease in swimming speed occurring within 1 m of HVDC cables would significantly affect Atlantic lumpfish migration or homing.

Cleaning behavior of ballan wrasse (Labrus bergylta) studied using sea lice dummies in large scale sea cages

The management of sea lice is one of the major challenges in farming of Atlantic salmon (Salmo salar) in Norway. Different methods are in use to remove sea lice from farmed salmonids during the grow-out phase in the sea, including mechanical, medicinal, and biological treatments. The use of farmed lumpfish (Cyclopterus lumpus) and ballan wrasse (Labrus bergylta) as cleaner fish is considered less stressful for salmon compared to other treatments. Documenting cleaning behavior in commercial sea cages is difficult. In this study, we used artificial sea lice dummies and camera to study cleaning behavior of farmed ballan wrasse in commercial sea cages during summer and autumn of 2021. Artificial sea lice dummies, 11–12 mm in length, and 26–27 mm total length including egg-strings, were attached to fixed positions on a dead salmon and placed in the sea cage. A total of 74 h of video recordings from three different cages were analyzed. We recorded inspections of the salmon by ballan wrasse, and any bites made at sea lice dummies or the salmon. Ballan wrasse rapidly showed interest in the model after introduction, with most of the first observations of behavioral events occurring within the first 30 min after the salmon were placed in the sea cage. An inspection of salmon rarely resulted in a bite on sea lice dummies (8%) and ballan wrasse was also observed biting on the dead salmon (12%). Cleaning behavior (i.e., bite on sea lice dummies) was on average ≈1 bite hour−1 and lice dummies placed on anterior ventral area were most susceptible to be bitten. This study uses a non-invasive method to study cleaner fish behavior, and it can in the future be used to investigate how different environmental factors impact cleaner fish behavior in large sea cages.

Variability in Parental Behavior of Lumpfish Cyclopterus lumpus (Cyclopteridae) under Changing Environmental Conditions

The most distinct features of reproductive biology of lumpfish Cyclopterus lumpus are defense and care for the clutch of fertilized eggs. In order to reveal the processes of male lumpfish defense of offspring, the quantitative assessment of temporal distribution of its behavior events under changing environmental conditions has been performed. Male behavior four types such as care for an egg clutch, defense behavior, locomotion, and rest are identified. Defense behavior is most variable, depending on the characteristics of an aggressor. It has been shown that the external factors affect the time taken for care rather than any change in certain actions. Under the favorable conditions, the male actions to care for an egg clutch represent repeating cycles, when the overall time spent on them may reach 99% of all time. Under the unfavorable conditions (strong currents and potential predators), the time of cycles tends to decrease to 55%. The environmental factor effects on the lumpfish behavior are described in terms of an algorithm of behavior, which can be used in modeling the energy intakes of a male lumpfish in the period of caring for offspring.

First detection of Cyclopterus lumpus virus in England, following a mortality event in farmed cleaner fish

Lumpfish are used routinely as cleaner fish to delouse farmed Atlantic salmon (Salmo salar) and are often translocated globally. In September 2021, an aquaculture production business in Dorset, England experienced considerable mortalities in consignments of lumpfish (Cyclopterus lumpus) imported from Norway. Following suspicion of infection with Cyclopterus lumpus virus (CLuV) by a veterinarian, commercial testing provided presumptive confirmation of a CLuV infection using reverse-transcription real-time polymerase chain reaction (RT-rPCR). Affected fish were later resampled by the Centre of Environment, Fisheries, and Aquaculture Science, Fish Health Inspectorate for screening of CLuV by RT-rPCR, and confirmation by conventional RT-PCR and sequence analysis. Additional samples were tested using isolation of viruses on cell cultures, bacteriology, histopathology, and PCR/rPCR techniques to investigate whether other pathogens of concern to the salmon aquaculture industry were also present. All samples tested negative for the presence of viral haemorrhagic septicaemia virus, infectious haematopoietic necrosis virus , nervous necrosis virus, infectious pancreatic necrosis virus , infectious salmon anaemia virus , ranavirus, and salmonid alphavirus. Four pools of ten samples tested positive by RT-rPCR for CLuV (Ct values between 19 and 29) and was confirmed using conventional RT-PCR. Sequence analysis showed that amplicons shared a 99.63 % match with the published sequences for CLuV. The CLuV has only recently been reported in aquatic animals and its full impact is not yet known. To the best of our knowledge this is the first report of CLuV in England.

Phaeohyphomycosis due to Exophiala in Aquarium-Housed Lumpfish (Cyclopterus lumpus): Clinical Diagnosis and Description.

Phaeohyphomycosis caused by Exophiala species represents an important disease of concern for farmed and aquarium-housed fish. The objective of this study was to summarize the clinical findings and diagnosis of Exophiala infections in aquarium-housed Cyclopterus lumpus. Clinical records and postmortem pathology reports were reviewed for 15 individuals from 5 public aquaria in the United States and Canada from 2007 to 2015. Fish most commonly presented with cutaneous ulcers and progressive clinical decline despite topical or systemic antifungal therapy. Antemortem fungal culture of cutaneous lesions resulted in colonial growth for 7/12 samples from 8 individuals. Amplification of the internal transcribed spacer region (ITS) of nuclear rDNA identified Exophiala angulospora or Exophiala aquamarina in four samples from three individuals. Postmortem histopathologic findings were consistent with phaeohyphomycosis, with lesions most commonly found in the integument (11/15), gill (9/15), or kidney (9/15) and evidence of fungal angioinvasion and dissemination. DNA extraction and subsequent ITS sequencing from formalin-fixed paraffin-embedded tissues of seven individuals identified E. angulospora, E. aquamarina, or Cyphellophora sp. in four individuals. Lesion description, distribution, and Exophiala spp. identifications were similar to those reported in farmed C. lumpus. Antemortem clinical and diagnostic findings of phaeohyphomycosis attributable to several species of Exophiala provide insight on the progression of Exophiala infections in lumpfish that may contribute to management of the species in public aquaria and under culture conditions.

Causes of Mortality and Loss of Lumpfish Cyclopterus lumpus

Data from research and commercial use of lumpfish were collected from the research facilities of Gifas (Inndyr, Northern Norway, 67.0° N, 14.0° E). The data were sourced from 12 main lumpfish groups subdivided into 66 subgroups (N = 160,729) delivered to Gifas between 2013 and 2020 and used in cleaner-fish research in (a) land-based facilities, (b) small-scale, or (c) large-scale sea pens. The data were standardised and organised into three main headings. Firstly, background information included transfer time, point of origin, mean starting weight and population size on arrival. Other information included to which site the lumpfish were transferred, volume of cage/tank, whether in the presence of salmon or not, stocking density, days at each site and water quality parameters. Causes of mortality were recorded, when possible, for each group, along with calculated mortality rates, patterns, and analytical information, along with imaging where available. Results show that causes of mortality varied within and between research sites. For lumpfish in hatcheries as well as for those deployed at small-scale sea pens, the primary cause of mortality was identified as pathogenic, while for lumpfish deployed at large-scale sea pens, transporting, grading and mechanical delousing were the primary causes of mortality. The results indicate that more research is required to clarify best practices both in commercial hatcheries and salmon cages and further understanding on lumpfish biological requirements and stress physiology is necessary to develop better methods that safeguard lumpfish welfare and meet their needs.

Salmon lice (Lepeophtheirus salmonis) in the stomach contents of lumpfish (Cyclopterus lumpus) sampled from Norwegian fish farms: Relationship between lice grazing and operational conditions

Cleaner fish are commonly used as a control measure against salmon lice infestations in salmonid farms. Lumpfish (Cyclopterus lumpus) is the most common cleaner fish species used in Norwegian farms. However, little is known about how different operational, including environmental, conditions affect the salmon lice grazing efficacy by lumpfish. In this paper, we analyse salmon lice (Lepeophtheirus salmonis) in the stomach contents of a large sample of more than 20,000 lumpfish from 80 different Norwegian farms. We investigate the proportion of lumpfish with salmon lice and the mean number of salmon lice in the stomach contents of the lumpfish. We further explore how the salmon lice contents vary with different factors like lumpfish weight, weight of salmonids, salmon lice abundance in the cage, cloud cover, and sea temperature. We find that 3.1% of the 24,693 lumpfish contained salmon lice. Most of the lumpfish with salmon lice in their stomach contents contained few (one or two) lice, while there were a few lumpfish which contained many salmon lice. We find more salmon lice in the stomach contents with increasing abundance of salmon lice in the sea cage, lower weight of the salmonids, and in clear weather. Interestingly, for the relationship between lumpfish weight and salmon lice in the stomach contents, we find increased salmon lice grazing from ca. 5 g up to an optimal weight of ca. 40 g, and then a decrease from 40 g. Surprisingly, we find no relationship between sea temperature and salmon lice per lumpfish. We find more salmon lice in the stomach contents of the lumpfish with comparatively high condition. By studying the factors associated with most efficient salmon lice grazing, our paper contributes to understanding how different operational factors affect salmon lice grazing by lumpfish. For controllable factors, the results thus contribute to guiding the best practice for use of lumpfish as a salmon lice control measure.

Comparing Body Density of Lumpfish (Cyclopterus lumpus) to Different Operational Welfare Indicators

Farmed lumpfish (Cyclopterus lumpus) are commonly used as cleaner fish in the salmonid aquaculture industry, but a knowledge gap exists with regards to their body density. Filling this knowledge gap is of importance, as the lumpfish has no swim bladder and thus relies on alternative methods for buoyancy, i.e., the body density difference between the fish and its surroundings. The aims of this study were to measure the body density of lumpfish and investigate the correlation between body density and different operational welfare indicators. A total of 138 lumpfish were sampled at five different aquaculture sites situated in the Faroe Islands. Weight in water and air was measured, body density was calculated, and operational welfare was assessed. The average body density of the juvenile lumpfish was 1.030 g mL−1. Fulton’s K, stomach score, and length were negatively correlated to body density, while the hepatosomatic index was positively correlated to body density. Liver colour was correlated to body density, but the groupings were too broad for a final definitive conclusion. The knowledge gained from this study might help the industry improve their understanding of the operational welfare indicators used for lumpfish. Additionally, the knowledge might also help the aquaculture industry improve their husbandry and feeding practices.

Monitoring ocean water quality by deployment of lumpfish (Cyclopterus lumpus) eggs: In situ bioaccumulation and toxicity in embryos

Fish embryos can bioaccumulate and are particularly sensitive to a wide range of contaminants, which makes them suitable sentinels for environmental biomonitoring. However, fish embryos are very rarely utilized in environmental monitoring surveys, possibly due to their fragility and seasonality. In the present work, we assessed the applicability of caged lumpfish (Cyclopterus lumpus) eggs for in situ biomonitoring of exposure and effects of organic contaminants focusing on polyaromatic hydrocarbons and phenolic compounds. Fertilized eggs (1 dpf) were transplanted for 17–19 days at different locations that differed in terms of contaminant load, depths and weather conditions, namely at three stations close to the city of Trondheim (two harbour areas and a one in the Fjord) and three stations at a coastal aquaculture facility. High survival upon retrieval after deployment showed that lumpfish eggs are relatively robust and survive encaging in different environments. Bioaccumulation of organic contaminants (PAHs and phenolic compounds) was measured and potential effects on hatching, development, survival and larvae morphometry were determined. Chemical analyses showed that especially PAHs were effectively accumulated in eggs in contaminated sites, with concentrations of ƩPAHs being 15 – 25 times higher in harbour areas compared to those at the aquaculture facility. A higher incidence of embryonic deformations was observed in the most polluted deployment location, but larvae morphometry revealed no evidence of toxicity related to pollutant body burden. In conclusion, the in-situ exposure method was proven to work well, making it attractive for implementations in environmental monitoring programs.

Incorporating concepts of biodiversity into modern aquaculture: macroalgal species richness enhances bioremediation efficiency in a lumpfish hatchery

Aquaculture is one of the fastest growing food producing sectors; however, intensive farming techniques of finfish have raised environmental concerns, especially through the release of excessive nutrients into surrounding waters. Biodiversity has been widely shown to enhance ecosystem functions and services, but there has been limited testing or application of this key ecological relationship in aquaculture. This study tested the applicability of the biodiversity-function relationship to integrated multi-trophic aquaculture (IMTA), asking whether species richness can enhance the efficiency of macroalgal bioremediation of wastewater from finfish aquaculture. Five macroalgal species (Chondrus crispus, Fucus serratus, Palmaria palmata, Porphyra dioica, and Ulva sp.) were cultivated in mono- and polyculture in water originating from a lumpfish (Cyclopterus lumpus) hatchery. Total seaweed biomass production, specific growth rates (SGR), and the removal of ammonium (NH<sub>4</sub> <sup>+</sup>), total oxidised nitrogen (TON), and phosphate (PO<sub>4</sub> <sup>3-</sup>) from the wastewater were measured. Species richness increased total seaweed biomass production by 11% above the average component monoculture, driven by an increase in up to 5% in SGR of fast-growing macroalgal species in polycultures. Macroalgal species richness further enhanced ammonium uptake by 25%, and TON uptake by nearly 10%. Phosphate uptake was not improved by increased species richness. The increased uptake of NH<sub>4</sub> <sup>+</sup> and TON with increased macroalgal species richness suggests the complementary use of different nitrogen forms (NH<sub>4</sub> <sup>+</sup> vs. TON) in macroalgal polycultures. The results demonstrate enhanced bioremediation efficiency by increased macroalgal species richness and show the potential of integrating biodiversity- function research to improve aquaculture sustainability.

In lumpfish We Trust? The Efficacy of Lumpfish Cyclopterus lumpus to Control Lepeophtheirus salmonis Infestations on Farmed Atlantic Salmon: A Review

In this review, we have systematized current knowledge about the effect of stocking lumpfish (Cyclopterus lumpus) as cleaner fish to control Lepeophtheirus salmonis infestations on farmed Atlantic salmon (Salmo salar L.). The review was prompted by recent reports in which the usefulness of lumpfish has been doubted, and the urgent need to investigate whether common lumpfish can be used to reduce L. salmonis numbers on farmed Atlantic salmon by active grazing on this species. Available published data clearly indicate that lumpfish graze on L. salmonis, and can significantly lower the lice burden in Atlantic salmon farming. It is possible to enhance the lice grazing behavior of lumpfish with the assistance of live feed conditioning prior to sea pen transfer, and with selective breeding. Data indicate that lice grazing of lumpfish is size dependent, and grazing effect is low for lumpfish larger than 200–250 g. Observations from large-scale rearing of Atlantic salmon in open sea cages in Norway, Iceland, the Faroe Islands, and Scotland also indicate that lumpfish can be effective in lowering infestations of L. salmonis on salmon. Overall, this present review reveals that lumpfish can actively contribute to lower numbers of L. salmonis on farmed Atlantic salmon.

CD45 in ocular tissues during larval and juvenile stages and early stages of V. anguillarum infection in young lumpfish (Cyclopterus lumpus)

Immune responses to infectious diseases impacting lumpfish (Cyclopterus lumpus) eye tissue are only starting to be studied at a molecular and histopathological level. In this study, we extend our understanding of lumpfish sensory organ anatomy, of components of the lumpfish nasal and ocular immune system and the nature of the intraocular response to Vibrio anguillarum infection. We have evaluated the expression of cluster of differentiation (CD) 45 protein, a tyrosine phosphatase, in larval and juvenile lumpfish tissues in order to spatially survey ocular and related head structures that may participate in early stages of intraocular immune responses. We provide here a histological mapping of the larval lumpfish nasal chamber system since its connectively with the eye though mucosal epithelia have not been explored. These results build upon our growing understanding of the lumpfish intraocular immune response to pathogens, exemplified herein by experimental nasally delivered V. anguillarum infection. CD45 is developmentally regulated in lumpfish eyes and periocular anatomy with early expression appearing in larvae in corneal epithelium and in nasal structures adjacent to the eye. Normal juvenile and adult lumpfish eyes express CD45 in the corneal epithelium, in leukocyte cells within blood vessel lumens of the rete mirabile, choroid body and choriocapillaris vasculatures. Experimental nasally delivered V. anguillarum infection led to qualitative and quantitative changes in CD45 expression in head kidney renal tubule tissues by 7 days post infection (dpi). The same animals showed redistribution and upregulation of corneal epithelial CD45 expression, corneal epithelial dysplasia and an increased frequency of CD45+ cells in ocular vasculature. Interestingly, while CD45 upregulation and/or CD45+ cell infiltration into inner ocular and retinal tissues was not observed under this experimental scenario, subtle neural retinal changes were observed in infected fish. This work provides new fundamental knowledge on North Atlantic teleost visual systems and vision biology in general.

Experimental infection trials with European North Atlantic ranavirus (Iridoviridae) isolated from lumpfish (Cyclopterus lumpus, L.).

European North Atlantic ranavirus (ENARV, Iridoviridae), is a ranavirus species recently isolated from lumpfish (Cyclopterus lumpus, L.), which are used as cleaner fish in Atlantic salmon (Salmo salar) farming in Northern Europe. This study aimed to investigate (1) the virulence of ENARV isolates from Ireland, Iceland and the Faroe Islands to lumpfish; (2) horizontal transmission between lumpfish; and (3) virulence to Atlantic salmon parr. Lumpfish were challenged in a cohabitation model using intraperitoneally (IP) injected shedders, and naïve cohabitants. IP challenge with isolates from Iceland (1.9× 107 TCID50 ml-1 ) and the Faroe Islands (5.9× 107 TCID50 ml-1 ) reduced survival in lumpfish, associated with consistent pathological changes. IP challenge with the Irish strain (8.6× 105 TCID50 ml-1 ) did not significantly reduce survival in lumpfish, but the lower challenge titre complicated interpretation. Horizontal transmission occurred in all strains tested, but no clinical impact was demonstrated in cohabitants. Salmon parr were challenged by IP injection with the Irish isolate, no virulence or virus replication were demonstrated. A ranavirus qPCR assay, previously validated for fish ranaviruses, was first used to detect ENARV in tissues of both in lumpfish and Atlantic salmon. This study provides the first data on the assessment of virulence of ENARV isolates to lumpfish and salmon, guidelines for the diagnosis of ENARV infection, and poses a basis for further investigations into virulence markers.

First record of biofluorescence in lumpfish (Cyclopterus lumpus), a commercially farmed cleaner fish.

This study is the first known observation of biofluorescence in the lumpfish (Cyclopterus lumpus). Individual lumpfish were illuminated with blue excitation lighting for photography with both hyperspectral and filtered multispectral cameras. All photographed juvenile lumpfish (n=11) exhibited green biofluorescence. Light emissions were characterised with two peaks observed at 545 and 613 nm, with the greatest intensity along the tubercles of the high crest and the three longitudinal ridges. Further research on the dynamics of biofluorescence through the lifecycle of this species is required.

A Screening Study on Effects Varying Dietary Macronutrient Composition on Gut Functions in Lumpfish (Cyclopterus lumpus)

Cultivation of lumpfish (Cyclopterus lumpus) as lice cleaner fish for salmon is now expanding. For successful cultivation of a new species, understanding the basic biology of digestive functions is vital to facilitate and optimize diet formulation. This paper presents results from two experiments conducted to deepen our knowledge on lumpfish intestine physiology. Experiment 1 was a 42-day feeding trial in which lumpfish were fed twelve different diets in the following ranges of macronutrients: Protein 43-68%, lipid 4-17%, and carbohydrate 6-17%. Intestinal tissue, gut content and liver were sampled from 6 fish per tank. The results showed that with increasing lipid level and corresponding decrease in protein level, there was a linear decrease in several of the observed biomarkers, including activity of brush border membrane digestive enzymes, expression of genes related to nutrient digestion and transport, ion exchange, immune regulation, and cell remodeling. Increased intracellular accumulation of lipid (steatosis) was observed in gut and liver with increasing dietary lipid level. Fewer effects were observed for increased dietary carbohydrate and corresponding decreased protein level. Experiment 2 was a two-week feeding trial for estimation of macronutrient digestibility in which lumpfish were fed three diets, all containing 55% crude protein, with lipid to carbohydrate ratio of the low lipid diet of 7.5%/18.3%, the medium lipid diet of 13.8%/14.6%, and high lipid diet of 18.1%/9.5%. Fecal samples were collected as pooled samples per tank. These results showed that fatty acid digestibility’s increased as dietary lipid level increased. Of note, starch digestibility decreased greatly as starch level increased, whereas protein digestibility did not change as lipid or starch level varied. Taken together, the present studies indicated that increasing lipid level in the diet with corresponding decrease in protein level affects digestion, absorption, and immune responses in the lumpfish intestine. Variation in dietary carbohydrate to protein level showed less effects, possibly due to low starch digestibility which makes the variation in available carbohydrates much less than the variation in the analysed level of dietary carbohydrates.

Replacement of fishmeal with plant protein in the diets of juvenile lumpfish (Cyclopterus lumpus, L. 1758): Effects on digestive enzymes and microscopic structure of the digestive tract

This study investigated the effects of plant protein concentrates on the activity of digestive enzymes and microscopic structure of the intestine of juvenile lumpfish. The experiment was carried out using triplicate groups of lumpfish of 7 g average initial body weight, to 40 g average final weight, after 54 days. Four experimental diets were used; a fishmeal (FM) based control diet and three test diets with the plant protein concentrates; soy protein concentrate (SPC) and pea protein concentrate (PPC) (1:1 ratio) replacing FM in proportions of 25% (PP25), 50% (PP50) and 75% (PP75), respectively. Nested ANOVA showed several significant treatment differences in histomorphometry. Overall, fish fed test diets exhibited several changes such as shorter mucosal fold height (MFH) in the anterior intestine (AI), increased number of goblet cells (GCs) and width of lamina propria (WLP) in distal intestine (DI), compared to control. Principal component analysis (PCA) on histological indices showed that all three treatment groups (i.e. PP25, PP50 and PP75) had significantly altered overall intestinal architecture, compared to the control group. The observed enteritis was negatively related with the condition factor (CF). Regarding enzyme activities fewer changes were observed across diets. Fish fed the PP50 diet exhibited an increased activity of leucine aminopeptidase (LAP) in the pyloric caeca and a decrease on chymotrypsin (CHY) in the mid intestine (MI) compared to the control. Nevertheless, the overall changes captured by PCA on enzymes were associated only with condition factor (CF) and not with the diets. Overall, histological evaluation confirmed that lumpfish intestinal morphometry was significantly altered by plant protein ingredients at 25%, 50% and 75% levels, but replacing of FM up to 50% did not affected the growth and the enzyme activities up to 75% inclusion level.

Ova lipid profiling and egg quality in wild and captive lumpfish, Cyclopterus lumpus (Linnaeus, 1758)

Lumpfish (Cyclopterus lumpus) serves an important role as cleaner fish for removing salmon lice in salmon aquaculture. For this use, cultivated lumpfish are preferred over wild-caught fish to avoid overexploitation of natural stocks and provide a stable production of good quality eggs and larvae. To support this, high quality eggs containing the necessary building blocks to support high fertilization success, development into a normal embryo and high hatching success is needed. Ova from wild-caught and captive lumpfish females were collected and assessed to identify how wild and domesticated lumpfish differ in terms of ova lipid profiles, egg and larvae quality. Wild-caught lumpfish displayed higher fertilization and hatching success compared to captive lumpfish, whereas other biological variables like egg size, egg/larvae dry weight and respiration, and larval morphometry, were not significantly different between wild and captive lumpfish. Ova lipid profiles (total lipid, lipid classes, fatty acid composition and lipidomics) can separate egg batches based on their geographic origin of wild-caught females and composition of diets used for captive broodstock (lipid and carbohydrate content). Multivariate statistics were applied to identify lipid markers that can be used to predict the quality of lumpfish ova. Lumpfish ova lipidomic profiles covaried with several biological parameters, indicating that the former can be used to predict the latter. Lumpfish eggs were mostly composed of triacylglycerides (TAGs) with some phosphatidylethanolamines (PEs) and phosphatidylcholines (PCs), and their lipid profiles were more sensitive to the different origins, mother weight/size and fertilization success than variables such as eggs size or larvae morphometric measures. PC and PE content of lumpfish eggs were positively correlated to both hatching success and fertilization rates, thus the lipidomic profiles, with some key highlighted lipid species were putative predictors of egg quality.

Characteristics of lumpfish (Cyclopterus lumpus) with high cleaning efficacy in commercial Atlantic salmon (Salmo salar) production

Cleaner fish such as lumpfish (Cyclopterus lumpus) are widely used as a biological method for delousing in Atlantic salmon (Salmo salar) aquaculture. Previous studies have mainly focused on the number of salmon lice (Lepeophtheirus salmonis) per salmon or on the proportion of individuals grazing on sea lice (L. salmonis and Caligus elongatus) and reported large variations in cleaning efficacy. Understanding what parameters cause these differences in cleaning efficacy is crucial to optimize the use of lumpfish as a biological delouser. In addition, it is uncertain how many sea lice are commonly ingested per lumpfish, even though this constitutes decisive information in the use of lumpfish for delousing. This study focused on the impact of lumpfish weight, diet and sex on cleaning efficacy in commercial Atlantic salmon net pens. A total of 2104 lumpfish were sampled from 8 Norwegian salmon farms over 2 years. Weight and sex was determined for each individual. Stomach content was visually identified and categorized as sea lice, lumpfish feed, salmon feed, biofouling organisms and zooplankton. Proportions of lumpfish with sea lice in their stomachs varied from 0 to 47% (average of 8.7% for the whole study) and the number of ingested sea lice varied from 0 to 120 (average of 0.6) between Atlantic salmon farms and sampling dates. Our results suggested that estimating the average number of sea lice ingested per lumpfish is necessary to determine cleaning efficacy. Weight was found to be a determining factor as lumpfish >300 g were very unlikely to consume sea lice. Individuals with the highest cleaning efficacy were small (< 100 g) and fed on additional prey items, mainly biofouling organisms. Lumpfish sex did not influence cleaning efficacy. We developed a simple model based on logistic regression analysis to predict lumpfish predict cleaning efficacy. The model predicted that maintaining lumpfish in net pens at a relatively small size (< 300 g) may raise grazing up to >1 sea louse per lumpfish.