Papers by Agnar Steinarsson
Journal of Fish Biology, Jun 1, 1998
Size, condition, and age of female-Icelandic cod Gadus morhua were correlated to the size of thei... more Size, condition, and age of female-Icelandic cod Gadus morhua were correlated to the size of their eggs and newly hatched larvae. A positive relationship was detected between egg size and some larval viability parameters, including the age at first feeding, successful development of a swimbladder, and specific growth rates during the first 15 days after hatching. These results reveal that the viability of cod larvae is related to attributes of the spawning females and that this information is important to our understanding of stock-recruitment relationships.
Canadian Journal of Fisheries and Aquatic Sciences, Mar 1, 2002
Results from laboratory experiments showed that food-unlimited growth rate (G) of Atlantic cod (G... more Results from laboratory experiments showed that food-unlimited growth rate (G) of Atlantic cod (Gadus morhua) declined linearly with fish weight (W) on a loglog scale at six different temperatures: 2, 4, 7, 10, 13, and 16°C. The intercept (αi) and slope (βi) of these regressions increased linearly with temperature (T), implying that G = αi W βi, where αi = γ1 + δ1T and βi = γ2 + δ2T. Nonlinear fit of the four-parameter model showed that γ1 was not significantly different from 0, and thus the following three-parameter model is suggested for the food-unlimited growth rate of cod ranging in size from 2 to 5000 g at any temperature from 2 to 16°C: G = (0.5735T)W(0.19340.02001T). The results indicate that temperature in this size range has a much greater effect on the growth rate of small juvenile cod than on that of larger cod. The model predicts that the optimal temperature for growth of cod decreases with increased size of fish, from 14.3°C for 50-g fish to 5.9°C for 5000-g fish. Growth curves were derived for cod at constant and seasonally variable temperatures. Weight-at-age was calculated for different temperatures.
Fish Physiology and Biochemistry, Feb 15, 2013
Induction of triploidy has been suggested as an effective tool to prevent spawning of farmed fish... more Induction of triploidy has been suggested as an effective tool to prevent spawning of farmed fish. This experiment examined the growth potential of triploid cod when reared communally with diploid ones after the juvenile stage. Pressure treatment was used to induce triploidy in a batch of cod eggs in April 2009. The resulting offspring were reared separately from their diploid counterparts until they reached the proper size for PIT tagging. At the age of 8 months, an equal number of 115 diploids (135.5 ± 3.95 g) and triploids (93.6 ± 2.63 g) were communally reared in a circular flow-through tank until the age of 22 months. By the end of this rearing period, diploids (1,002.4 ± 39.9 g) were significantly heavier than triploids (654.6 ± 27.7 g), but the specific growth rate did not differ significantly during the growth trial. Gonadal development at the age of 22 months was also lower among triploids than diploids, especially for females (5.3 and 91.9 %) but also for males (32.5 and 72.7 %). Sterility among female triploids was evident by the reduced size and dysfunctional gonads, but gonadal development in male triploids was less suppressed. Prevalence of body deformities was, however, significantly higher among triploids (62.6 %) than diploids (33.9 %). Higher prevalence of deformities in triploid cod underlines the need for further fine-tuning of the triploidization procedure or finding other methods of sterilization. At present, triploid cod are still far from being established as an alternative for commercial production.
Zenodo (CERN European Organization for Nuclear Research), Jun 30, 2022
Minimizing the stress of salmonids during handling and before slaughtering can be extremely impor... more Minimizing the stress of salmonids during handling and before slaughtering can be extremely important for welfare, survival and growth, as well as to ensure overall quality and shelf-life of the final products. Stress during treatment, e.g., against lice, can reduce the resistance of fish to infections and cold seawater as well as reduce growth which may take the salmon some time to recover from stress and start feeding again. If the pumping of fish for slaughter causes a lot of stress, it can affect the quality of the products. Animal welfare is also becoming more important in aquaculture with increased welfare demands from the consumers. It is known that vacuum pumps, that are most commonly used in the aquaculture industry today, cause considerable stress, loss and poor quality, as pumping causes a lot of discomfort for the fish. Companies have therefore been searching for an alternative to vacuum pumping for some time. The Icelandic company Skaginn 3X has for some time been developing a so-called Archimedes pump to replace vacuum pumps. In this project, a prototype of the Archimedes pump (called ValuePump) was made, and then compared to a conventional vacuum pump. The pumping stress of fish was measured by cardiac sensors along with the measurement of a stress hormone Over a 4-week period, 100 salmons (1 kg average weight) were pumped once weekly with either pump, including 20 salmons implanted with heart rate loggers from Star-Oddi. Experiments were carried out in the facilities of the Marine and Freshwater Research Institute in Reykjanes under supervision of specialists in aquaculture and the use of cardiac sensors. The results showed a significant difference in heart rate recovery between the two groups. There was a large increase in heart rate immediately after pumping but the ValuePump group recovered more quickly to pre-pumping levels. Pumping with the vacuum pump caused a larger and longer stress effect then an applied max stress chase protocol. There was also a considerable visible difference between the two groups, where the vacuum pump fish were injured or even dead after pumping, swimming on the side or upside down for hours after pumping. The ValuePump fish, however, received no visible physical damage from the pumping and seemed fit. The results of the comparative studies indicate very positive results, but further studies are however needed to validate the results. It is apparent that salmon pumped with ValuePump is faster to recover than when pumped with vacume pumps and is as results faster to start feeding again after handling. Results regarding pumping of fish for slaughtering are not as comprehensive and need to be studied further, particularly by analysing fish that has reached slaughter size and preferably in real industry setting.
Journal of Fish Biology, 1998
Size, condition, and age of female-Icelandic cod Gadus morhua were correlated to the size of thei... more Size, condition, and age of female-Icelandic cod Gadus morhua were correlated to the size of their eggs and newly hatched larvae. A positive relationship was detected between egg size and some larval viability parameters, including the age at first feeding, successful development of a swimbladder, and specific growth rates during the first 15 days after hatching. These results reveal that the viability of cod larvae is related to attributes of the spawning females and that this information is important to our understanding of stock-recruitment relationships.
Aquaculture Research, 2010
This work aimed at validating the use of two prospective probionts (Arthrobacter sp. and Enteroco... more This work aimed at validating the use of two prospective probionts (Arthrobacter sp. and Enterococcus sp.) at early stages of cod (Gadus morhua L.) rearing. Ova at late post-fertilized stage and larvae during their ¢rst 4 weeks of life were bathed with both probionts, isolated previously from the cod-rearing environment. This treatment was compared with groups fed rotifers supplemented with a commercial probiotic (Remus s) and those untreated. Microbiological analyses (total viable counts, presumptive Vibrio and lactic acid bacteria) were performed in rearing systems and larval survival, growth and development were assessed. Larval development was evaluated by proteolytic activity of larval lysates and immunological analysis of important proteins: apolipoprotein A-I, haemoglobin, C-reactive protein, C3 and cod serum proteins. Bacterial bathing led to a signi¢cantly higher larval weight, length and culturable microbial load in larval gastrointestinal (GI) tract when compared with the control and Remus groups. Development occurred earlier in bathed larvae. However, their survival was negatively a¡ected compared with the control group, but was signi¢cantly higher than for the Remus group. The non-pathogenicity of both probionts was demonstrated by intraperitoneal injection of 13 g cod juveniles. The results suggest that Arthrobacter and Enterococcus probionts a¡ected the larval GI microbiota and contributed to growth, development and digestion, either directly or indirectly.
Ágrip á íslensku: Markmið A-hlutans var að auka hagkvaemni við stríðeldi þorsks með því að auka l... more Ágrip á íslensku: Markmið A-hlutans var að auka hagkvaemni við stríðeldi þorsks með því að auka lifun hrogna/lirfa og stuðla að auknum vexti lirfa í startfóðrun. Niðurstöður sýna að samsetning örveruflórunnar skýrði betur afföll en heildarörveru-eða Vibrio talningar. Víðtaek greining á örveruflóru eldiskerfa og afkomutölur á lirfustigi leiddu til ákvörðunar á aeskilegum og óaeskilegum bakteríum. Efnamaelingar við þorskeldi á hrogna-og lirfustigi sýndu að lítil uppsöfnun efna átti sér stað í eldisvökvanum, nema við upphaf þurrfóðrunar. Val baetibaktería var ákveðið út frá ákveðnu skimunarferli og vaentanlegri notkun við þorskeldi. Notkun baetibaktería við böðun hrogna og/eða lirfa var skoðuð en samfelld böðun frá hrognastigi áfram yfir í lirfustigið leiddi yfirleitt til betri afkomu, meiri vaxtar og lífsþróttar. Einnig hafði notkun baetibaktería áhrif á örveruflóruna og þroskun lirfa stuttu eftir klak, sem var m.a. staðfest með maelingum á próteinum úr ónaemiskerfinu. Notkun baetibaktería í seiðaeldi var könnuð og benti hún til aukins vaxtarhraða. Ekki tókst að sanna að aukið sjúkdómsþol naeðist með notkun baetibaktería við seiðaeldi, en jákvaeðar vísbendingar fengust þar um. Helstu flöskuhálsar við þróun forvarnaraðferða voru lifandi faeðudýrin, sem höfðu í för með sér mikið örveruálag. Þróun probíotískra hjóldýra með öðrum baetiörverum gaf ekki góða raun. Athuganir á sýkingarmaetti baetibakteríanna í þorskseiðum sýndu að þaer ollu hvorki sjúkdómseinkennum né orsökuðu dauða.
Journal of Marine Science and Engineering, 2022
The effects of early thermal environment on growth, age at maturity, and sexual size dimorphism i... more The effects of early thermal environment on growth, age at maturity, and sexual size dimorphism in Arctic charr (Salvelinus alpinus) are investigated. This study is a 654-day long rearing trial split into two sequential experimental phases termed EP1 and EP2 and lasting 315 and 339 days, respectively. EP1 started at the end of the yolk sac stage when the experimental fish were divided into three groups and reared at different target temperatures (7, 10 and 12 °C). During EP2, all groups were reared at the same temperature (7–8 °C) until harvest (~1300 g). Growth rates increased with temperature from 7 to 12 °C, and at the end of EP1 the 12C group had 49.0% and 19.2% higher mean weight than groups 7C and 10C, respectively. Elevated early rearing temperatures were, however, found to cause precocious sexual maturation and reduce the long-term growth performance. At the end of EP2, the 7C group had 3.6% and 14.1% higher mean weight than 10C and 12C, respectively. Elevated early rearing ...
Styrktaraðilar / funding: Technology Development Fund and AVS R&D Fund of Ministry of Fisheries i... more Styrktaraðilar / funding: Technology Development Fund and AVS R&D Fund of Ministry of Fisheries in Iceland Ágrip á íslensku: Nýlegar rannsóknir hafa leitt í ljós að bestu aðstaeður við framleiðslu lirfa gefi seiði af betri gaeðum og að vaxtarforskot á fyrstu stigum eldisins skili sér að einhverju leiti á seinni vaxtarstigum. Meginmarkmið þessa verkefnis er að skilgreina bestu aðstaeður við eldi þorsklirfa á Íslandi og nýta í því markmiði margvíslegar aðferðir við lausn helstu vandamála sem eru tengd framleiðslu þorsklirfa í dag. Þessi skýrsla fjallar um þá verkþaetti sem Matís ohf. tók þátt í sem m.a. var að rannsaka áhrif auðgunar fóðurdýra með baetibakteríum og próteinmeltu á vöxt, þroska, ónaemisörvun og meltingarflóru lirfa svo og rannsóknir á áhrifum mismunandi frumfóðrunar á vöðvavöxt sem unnið var í samvinnu við Hafrannsóknastofnunina. Niðurstöður gefa vísbendingar um að byrjun þurrfóðurgjafar seint eða um 50 dph gefi ekki lirfum vaxtarforskot og að það sé naegilegt að fóðra með Artemiu þar til 40 dph. Þurrfóðurgjöf frá 30 dph leiddi til minni vaxtar og aukinnar tíðni byggingargalla. Auðgun fóðurdýra með frostþurrkaðri blöndu tveggja baetibakteríustofna hafði ekki áhrif á samsetningu bakteríuflóru lirfa og stofnar náðu ekki fótfestu í meðhöndluðum lirfum. Hinsvegar má gera ráð fyrir að léleg hrognagaeði hafi haft áhrif á niðurstöður meðhöndlunar. Niðurstöður tilrauna staðfesta fyrri niðurstöður um jákvaeð áhrif auðgunar fóðurdýra með próteinmeltu á afkomu og þroskun lirfa.
Aquaculture, 2018
Potential interactive effects of ammonia and CO 2 on growth performance and feed utilization in j... more Potential interactive effects of ammonia and CO 2 on growth performance and feed utilization in juvenile Atlantic cod (Gadus morhua L.
Aquaculture, 2019
The effects of temperature and growth hormone (GH) implantation on growth of juvenile Atlantic wo... more The effects of temperature and growth hormone (GH) implantation on growth of juvenile Atlantic wolffish (Anarhichas lupus) were investigated. The year-long study had three sequential experimental phases (EP) termed EP1, EP2 and EP3, lasting for 6, 9 and 37 weeks, respectively. The experimental fish were divided into four groups and reared at different target temperatures (3, 7, 11 and 15°C) during EP1 and EP2, but at a constant temperature of 7°C during EP3. At the beginning of EP2, half of the fish from each group was implanted with formulation of recombinant bovine GH (Posilac®), while the other half was sham-implanted with vehicle. The optimal temperature for growth (T opt.G) of early juveniles (geometric mean weight 7.5 g) was determined as 12.1°C during EP1, while the upper critical temperature (Tc) was concluded to be very close to 15°C, as fish at that temperature had stunted growth, increased mortality and showed external signs of skeletal deformities. Thus, the species was found to be relatively stenothermic during the early juvenile stages and therefore vulnerable to relatively modest increases in environmental temperature above T opt.G. At 15°C, GH implantation had no effects on growth rate. This indicates that the high allostatic load at this temperature leaves no scope for increased growth. In contrast, at lower rearing temperatures, the GH implantation had substantial, long-term effects on growth rate and induced remarkably similar relative growth stimulation at 3, 7 and 11°C, suggesting a temperature-independent mechanism for the growth-promoting effects of GH.
Aquaculture Nutrition, 2013
ABSTRACT High larval mortalities and anatomical deformities are among the major obstacles restric... more ABSTRACT High larval mortalities and anatomical deformities are among the major obstacles restricting the development of Atlantic cod (Gadus morhua) aquaculture. The immune system of cod larvae is poorly developed at hatch, and innate immune parameters are therefore of importance for defence against environmental microorganisms. Two separate experiments were conducted with bioencapsulation of the live feed of cod larvae using a pollock (Pollachius virens) protein hydrolysate. Offering peptide enhanced live feed to larvae during the first weeks of exogenous feeding promoted larval development, with reduced incidence of severe deformities to 3.0% as compared with 9.6% deformities observed in the control group at 160 days posthatch. The production and distribution of IgM and lysozyme were furthermore increased in larvae fed peptide enhanced feed compared with control larvae. IgM was predominantly detected in the foregut and the epithelial lining of the digestive tract as well as in the epidermal mucus of the skin. Lysozyme was mainly detected in the epidermal mucus of the skin and in the foregut. Overall, the results indicate that live feed enhancement using a protein hydrolysate derived from pollock may reduce deformities and promote normal development during early production stages of cod larvae.
Journal of Fish Diseases, 2006
Cod larval culture is currently hampered by high mortalities in the first 2–3 weeks after hatchin... more Cod larval culture is currently hampered by high mortalities in the first 2–3 weeks after hatching, often due to infectious diseases. The immune system of cod is not fully competent until 2–3 months after hatching. Conventional vaccination is, therefore, not of value before this time, and the larvae are wholly reliant on non‐specific parameters for their defence against infection. A range of substances, generally derived from bacterial, fungal or plant origin, can activate these non‐specific parameters. During three hatching seasons, 2001–2003, at the Marine Institute's Experimental Station, Stadur, Grindavik, Iceland, the effects of several immunostimulants on survival and disease resistance of cod larvae and juveniles were examined. Both bathing treatments and administration in the feed were used. One of these substances, lipopolysaccharide (LPS), isolated from the bacterium Aeromonas salmonicida (ssp. salmonicida or achromogenes), appeared in some instances to improve surviva...
Journal of Fish Biology, 1999
The optimal temperatures for growth of four groups of hatchery‐reared cod larvae (geometric mean ... more The optimal temperatures for growth of four groups of hatchery‐reared cod larvae (geometric mean weight: 73, 191, 249 and 251 μg), reared on rotifers at four or five constant temperatures between 4 and 16° C for 14, 12, 9 and 16 days were 9.7, 12.3, 12.7 and 13.4° C, respectively. The maximum growth rate also increased with size and was 6.5, 9.6, 11.7 and 11.3% day−1 for the respective size groups. The optimal temperature for survival was 8.5–8.8° C for all size groups. The results indicate an opposite relationship between (1) size and optimal temperature for growth and (2) size and maximum growth rate of cod larvae, to that observed for juvenile and immature cod.
Journal of Applied Microbiology, 2010
Aims: To study the effect of ova disinfection, antibiotic and microbial treatments on the dominan... more Aims: To study the effect of ova disinfection, antibiotic and microbial treatments on the dominant cultivable cod rearing microbiota at pre-and posthatch stages, determining some virulence-related phenotypic traits among bacterial isolates and their relation to larval survival. Methods and Results: Sampling of rearing systems (rearing water, ova, larvae, feeds and supplement) for analysis of cultivable microbiota took place at early stages in 2004 and 2005. Cultivation, phenotypic and genotypic (16S rRNA gene) analyses were performed. The production of putative virulence factors (PVFs), including haemolysin, siderophores and quorum-sensing signals, by bacterial isolates was investigated and related to larval survival. The study was performed during two spawning seasons, evaluating current hatchery practices (ova disinfection and antibiotic treatment of unhealthy larvae) and specific putative probiotics applied to ova and larvae or rotifers. A diversified microbiota (75 operational taxonomic units, OTUs) was observed in cod rearing systems influenced by the feeds and treatments, with prevailing c-Proteobacteria prior to hatching towards a multiphyla microbiota posthatch. Phenotypic tests demonstrated the heterogeneity within some OTUs. Multivariate analysis of survival data in larval silos and the corresponding larval microbiota was used to divide the genotypic groups into beneficial ⁄ harmless and detrimental ⁄ opportunistic clusters. PVFs were common among the proposed detrimental ⁄ opportunistic OTUs. Conclusions: The results clearly demonstrate the influence of exogeneous feeding and treatments on larval gastrointestinal microbiota and the role of bacteria in larval survival. Significance and Impact of the Study: Increased understanding of the microbiota in rearing systems may contribute to successful implementation of microbial management in cod aquaculture.
Journal of Applied Microbiology, 2010
Aims: To assess the effects of bacterial treatment at the earliest stages of cod rearing on the m... more Aims: To assess the effects of bacterial treatment at the earliest stages of cod rearing on the microbial load, larval development and performance, testing three bacterial strains (Carnobacterium divergens V41, Arthrobacter sp. and Enterococcus sp.) in vivo that were previously shown to have inhibitory potential towards fish pathogens in vitro. Methods and Results: A bacterial mixture was added eight times to the rearing water from the prehatch to the mid-larval stage (a 38-day period). Microbiological analysis of ova, larvae and rearing water was performed regularly. Larval performance and development were evaluated by survival rate, hypersalinity tolerance and physiological measurements. Different larval survival rates were observed within and between treatments, and possibly explained by variations in larval microflora and established probionts. Larvae from one silo, which had been bathed in the bacterial suspension, showed the highest survival rate (42AE1%), lowest Vibrio levels, and were significantly heavier (19AE3%) and more stress tolerant than control larvae (P < 0AE01). This coincided with the intestinal establishment of two of the tested bacteria. Conclusions: Arthrobacter and Enterococcus strains added regularly to the rearing water from the postfertilized egg stage can become established in larval gastrointestinal tract. The Enterococcus strain was associated with increased larval growth, performance and microflora control, indicating its probiotic nature. Significance and Impact of the Study: Regular application of autochthonous probionts may promote larval welfare, development and stress tolerance at early stages, hence increasing production yield in intensive cod larviculture.
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Papers by Agnar Steinarsson