Department of Biology Fisheries ecology and Aquaculture

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<ul><li><p>CHALLENGES IN THE REARING OF EUROPEAN HAKE MERLUCCIUS MERLUCCIUS</p><p>AUDREY J. GEFFEN, ANNE-LAURE GROISON, LENE KLEPPE, University of Bergen, Norway. HLNE du PONTUAL, AURELIE JOLIVET, Ifremer, STH/LASAA, Brest, France. RAGNAR SALTE, MerluNor, Brekke / Norwegian University of Life Sciences, s, Norway.Department of BiologyFisheries ecology and Aquaculture </p></li><li><p>Why in Norway? Good technical foundation, Good access to local wild populations</p></li><li><p>Short history of hake larval rearing 1997, 1998, 1999 - Reidun Bjelland and Anne Berit Skiftesvik (Institute for Marine Research Austevoll Research Station) Bjelland &amp; Skiftesvik 20062005 Anne Laure Groison (Department of Biology, UiB)Ragnar Salte (Department of Animal and Aquacultural Sciences, Norwegian University of Life Sciences) establishes MerluNOR and captive broodstock2006 Anne Laure Groison (UiB), Aurelie Jolivetand Hlne du Pontual (Ifremer, Brest)2007 Natural Spawning!!!! MerluNor and IfremerAurelie Jolivet and Hlne du Pontual (Ifremer, Brest)Audrey Geffen (UiB)2008 Natural Spawning at MerluNOR - UiB </p></li><li><p>Status and challengesOne captive broodstockOne instance of successful rearingLarval rearing until 25dph, past first feeding</p><p>Technical ChallengesBiological ChallengesPhotos: J. Skadal</p></li><li><p>Technical Challenge -1Eggs have been obtained by stripping wild-caught fish</p></li><li><p>Captive spawningCaptive populations established at Brest, France and at Brekke, Norway</p><p>Egg production in both populations</p><p>Fertilized eggs leading to larvae produced by Brekke groupMerluNor Brekke, Norway</p></li><li><p>Egg productionCaptive spawning pattern compares well with field dataSpawning first observed at Brest and at Brekke in 20072 Females at Brekke produced 17 batches in 2007, 3 batches so far in 2008</p></li><li><p>Technical Challenge -2</p></li><li><p>Biological Challenges 1: Growth PatternHatching Day 0</p></li><li><p>Biological Problems 2: 3 Dph10 Dph12 DphEstablishment of feedingPhotos: J. Skadal19 Dph</p></li><li><p>Challenges?Broodstock, Incubation</p><p>Feeding: Prey size, swimming behaviourRearing conditions: light levels</p><p>Coombs &amp; Mitchell, 1982 Light levels In tanks ~ 2-5 mol s-1 m-2 At surface 8 - 15 mol s-1 m-2</p></li><li><p>Thanks!</p><p>My talk may be rather brief because rearing hake is 80% wishful thinking, and 20% data</p><p>In other words, big on the challenges facing many new speciesWhy is there an interest in Hake aquaculture well for commercial reasons of course..high prices and high marketability</p><p>Also, I believe that this is a very interesting species in terms of energetics, development, and behavioural studies</p><p>In Norway there is virtually no market, but there are easily accessed populations, and experience with developing new species with little available information (halibut, for example)Here is a short overview of the laboratory work on hake:</p><p>Over 3 years Reidun and Anne Berit worked with several batches of eggs and finally produced juveniles, using silos they are still the only one to have done so</p><p>In 2005 Anne Laure started working to rear larvae at UiB, and Ragnar Salte established MerluNOR. Both MerluNOR and Ifremer began broodstock collection</p><p>In 2006 larval rearing experiements were attempted at Ifremer and at UiB, based on gametes collected from wild fish</p><p>In 2007 Natural spawning was observed in the broodstocks at Ifremer and MerluNOR but fertilization only succesful at MerluNOR. This led to larval seasons at UiB, and also at Ifremer based on gametes collected from wild fish</p><p>And the MerluNOR fish have started spawning again this year three batches so far, and larval experiments are underway in large tanks</p><p>The status of hake culture now - 10 years after the first attempts ?</p><p>Some achievements, but still facing challenges, and these are both Technical and BiologicalThere are quite a few challenges to be overcome for commercialization of hake production or even to get fish in captivity</p><p>The first challenge is to assemble a broodstock capture of live fish is difficult, but successful protocols have been developed in France and Norway. Numbers are still too few to talk about manipulated conditions or diets, or even egg quality yet. </p><p>At Ifremer, two groups were established - 2 and 10 individuals, and held for 3 and 2 years respectively. They were acclimated to formulated feed. Fish in the larger group grew 13 cm / year, confirming the rapid grwoth potential of hake.</p><p>An additional group of about 15 fish were kept and fed with natural forage prey for 1.5 years, and grew 18 cm/year.</p><p>Although there are a number of studies on hake reproduction, these are mostly fecundity studies. More data on the reproductive biology of the different populations is needed, and in fact the fecundity and spawning fraction estimates for different populations do show local variations. Some authors quote 4% spawning fraction, and others 18 20%</p><p>Spawning frequency in the wild is estimated to be every 5-7 days at the height of the spawning season, decreasing to every 10 days later in the season. This interval estimate is based on histological examination, and egg survey data. RASER project</p><p>The spawning data from Brekke, which is based on 2 females in 2007 and one female so far in 2008, indicate that the interval is 7 10 daysThe second challenge is in the incubation of the eggs. The eggs vary in buoyancy during development, and during the first few days tend to float above the water surface. Thus, the usual methods of incubation are not appropriate, and better results are obtained with a strong horizontal flow rather than upwelling. In fact, the eggs are hydrofugal which is described as adhering to the surface tension of the water. Coombs &amp; Mitchell 1982 claim that this is not a question of buoyancy, but a property of the egg surface. This is the case also for eggs sampled in plankton surveys, both for fresh eggs and after preservation in formalin, so it is a natural condition. </p><p>However, this seems to be less of a problem as the eggs developEven if technical problems are solved, there are still some major biological challenges</p><p>First is the development required during yolk nutrition because Hake hatch without functioning eyes, mouth or gutThe growth pattern is problematic over the first 7-10 days there is little change in length though morphological changes are huge</p><p>This pattern makes it hard to determine whether the larvae have successfully established feeding But in fact this pattern appears also to be the case in the wild</p><p>I should say at this point that hake have a rather narrow temperature range 10 12 degrees is where they seem to thrive, in the field and lab Likewise looking at weight at age, it is clear that yolk nutrition can sustain these guys for a long time, and that hake have a strategy of putting everything into developing their feeding apparatus ------ But then forget to feed!</p><p>It is also clear that there is a breakpoint around 12 days after hatching when feeding must start in order to support eventual growth Again, the small amount of data available indicates that the pattern obtained in the lab, for both successful and unsuccessful attempts, is similar the pattern seen in natureThe success of first feeding - and more importantly the establishment of feeding, is a major challenge that has been overcome only once thus far.</p><p>Hake larvae put lots of energy into development of jaw and digestive system, little growth is seen during the first few weeks. Feeding conditions are likely important but prey size may not be a big issue just look at the size of the mouth. Speed and swimming behaviour of the prey may be important</p><p>Tempting to say that the poor results thus far are a quality issue, but the same pattern is seen in the wild - So, despite several attempts to capture and keep hake, only 2 populations have spawned, and only one successfully but it is possible</p><p>Rearing conditions have had success in large volumes only is there an issue with light levels? Look at the natural distribution of the larvae:</p><p>Finally, feeding is the biggest challenge perhaps not first feeding, but continuation finding the right prey?</p></li></ul>