Improvement of rearing conditions for juvenile lobsters (Homarus gammarus) by co-culturing with juvenile isopods (Idotea emarginata)

Abstract

Growth conditions of the juvenile lobsters, Homarus gammarus, were optimized in view of a restocking project of the lobster population at Helgoland (German Bight, North Sea) aimed to produce more than ten thousand juvenile lobsters per year. Growth and survival rates of juvenile lobsters depend on diet, temperature and water quality. In the present study, diet at optimum temperature was considered, but special emphasis was placed on the optimization of cleaning and feeding methods from both an economical and ecological point of view. Six dietary treatments of juvenile lobsters (each n = 99) were tested in individual compartments in a semi-closed re-circulation system at around 20°C. Lobsters were fed with combinations of two diets, newly hatched Artemia sp. nauplii and minced crabs Cancer pagurus (whole carcasses), every 2 or 4 days until a carapace length of 10 mm was reached. During the experiment (max. 105 d), juvenile isopods, Idotea emarginata, were constantly present in the lobster boxes. More frequent feeding significantly increased growth rates of the juvenile lobsters while different feeding combinations had no effect. The highest growth rate (0.091 ± 0.02 mm CL day − 1 ) was at a feeding frequency of every 2 days for each diet. At this rate the carapace length of 10 mm was reached in 68-71 days. The survival rate of the juvenile lobsters ranged from 90-97%. The diet consisting of C. pagurus was most cost-efficient and was obtained as discards from the crab fishery at Helgoland. The co-culture of juvenile lobsters with juvenile isopods I. emarginata as "cleaning organisms" was ideally suited for the rearing of lobsters and reduced the maintenance time by 50%. The isopods also served as supplementary diet.

A mark-recapture study of hatchery-reared juvenile European lobsters, Homarus gammarus, released at the rocky island of Helgoland (German Bight, North Sea) from 2000 to 2009

“…The larvae reached the first juvenile stage (stage IV) approximately 15 days after hatching (Schmalenbach and Franke, 2010). After moulting to stage IV the animals were placed in separate compartments and they were reared to a carapace length of about 15 mm using techniques described in Schmalenbach et al (2009). This rearing specification and release size were broadly similar to those described in Burton et al (1994) and Bannister and Addison (1998) in the UK.…”

Deformities in larvae and juvenile European lobster (<i>Homarus gammarus</i>) exposed to lower pH at two different temperatures

“…After five months of exposure, 44 and 21 % of the juveniles were deformed in medium and high pCO 2 treatment, respectively. Deformities in lobster larvae and juveniles have not previously been reported, either in European or American lobster, although the scientific community have long-term experience in husbandry of these two species (Gruffydd et al, 1975;Capuzzo and Lancaster, 1979;Latrouite and Lorec, 1991;Addison and Bannister, 1994;Uglem et al, 1995;Agnalt et al, 1999Agnalt et al, , 2004Nicosia and Lavalli, 1999;Linnane et al, 2000;Jørstad et al, 2001;Wickins and Lee, 2002;Kristiansen et al, 2004;Jørstad et al, 2005;Agnalt, 2008;Arnold et al, 2009, Ries et al, 2009, Schmalenbach et al, 2009, Keppel et al, 2012. Wickins et al (1995) did report moulting abnormalities in European lobster larvae in relation to testing different diets, but with no further description of what the abnormalities were.…”

Morphological and histochemical examination of male and female gonads in Homarus gammarus (L. 1758)

“…These include: growth, reproduction, movement and abundance of the European lobster, H. gammarus, at the rocky island of Helgoland, North Sea [8], improvement of rearing conditions for juvenile lobsters by co-culturing with juvenile isopods (Idotea emarginata) [3], growth, reproductive cycle, and movement of berried European lobsters in a local stock off southwestern Norway [9], reproduction in the European Lobster [10], studies on the developmental conditions of the European lobster [8], and variation on size at onset of egg production [11]. However, basic studies concerning the male and female reproductive system, gonad structure and histochemistry are missing.…”

“…This species also is widely distributed throughout the Mediterranean Sea, among the Mediterranean islands and east to the point where the Dardanelles meet the Aegean Sea [1,2]. H. gammarus is an endangered species in Helgoland [3] and has high commercial value as food [3,4]. Overfishing, habitat destruction, increasing sea tempratures and increased industrial pollution cause difficulties for the reproduction of H. gammarus and its natural stocks are harmed accordingly [5].…”