Saltwater performance of triploid Atlantic salmon Salmo salar L. brown trout Salmo trutta L. hybrids

Survival and growth in a saltwater net-pen of sexually immature triploid Atlantic salmon Salmo salar L. brown trout Salmo trutta L. hybrids was comparable to that of immature diploid Atlantic salmon. Following 17 months of freshwater rearing, the experimental fish were individually tagged and transferred to a saltwater net-pen where they were raised communally for 376 days. Initial and final average weights were 158 and 760 g per fish for the diploid Atlantic salmon and 209 and 1010 g per fish for the triploid hybrids; weights for the hybrids were significantly larger in both cases (α= 0.05). Survival from transfer to harvest was 43% for the Atlantic salmon and 48% for the hybrids. Average specific growth rate of fish which survived to harvest was 0.42% day^-1 for Atlantic salmon and 0.41% day^-1 for hybrids; these values were not significantly different. No significant differences were observed in average condition factor and dress-out percentage between crosses. Average gonadal weights and gonadosomatic indices were not significantly different for male diploid Atlantic salmon, female triploid hybrids and male triploid hybrids, but were significantly greater for female Atlantic salmon.     

Environmental parameters controlling growth of Ostrea edulis L. and Pecten maximus L. in suspended culture

Oysters (Ostrea edulis) and scallops (Pecten maximus) were grown in lantern nets at three stations in Birterbuy Bay, Co. Galway, Ireland. Shell and tissue growth and mortalities were recorded over a period of 18 months. Sea water temperatures, salinities, particulate organic carbon concentrations (POC), particulate organic nitrogen (PON) concentrations, particle concentrations and volumes of the seston and current speeds were recorded during a growing season. Differences in growth between stations are explained in terms of differences in temperature, organic carbon content of the seston and current speeds.     

庸鲽的习性及其养殖前景

庸鲽 (ＨｉｐｐｏｇｌｏｓｓｕｓｈｉｐｐｏｇｌｏｓｓｕｓＬ .) ,英文名Ａｔｌａｎｔｉｃｈａｌｉｂｕｔ,是世界上最大的比目鱼 ,经济价值很高 ,现是西北大西洋地区最受欢迎的比目鱼类之一。它口感独特 ,风味良好 ,在欧洲市场同鲑鳟鱼类一样名贵 ,尤其是鳍条 ,烤或炖起来吃更是风味独特。目前在北欧和北美的部分地区已形成一种养殖产业 ,达到企业化生产水平 ,并逐步向其它各地推广 ,已经引起广大养殖业者的关注。1　分类地位与形态特征庸鲽属于鲽形目 (Ｐｌｅｕｒｏｎｅｃｔｉｆｏｒｍｅｓ)、鲽科(Ｐｌｅｕｒｏｎｅｃｔｉｄａｅ)、庸鲽属 (…     

Aquaculture Biotechnology,by Garth L. Fletcher,Matthew L. Rise,and Wiley-Blackwell

FOOD MICROBIOLOGY: FUNDAMENTALS AND FRONTIERS, Second Edition. Edited by Michael P. Doyle, Larry R. Beuchat, and Thomas J. Montville. Washington, DC, ASM Press, 2001, 888 pages. $124.95. Reviewed by Keith W. Gates.     

Efficacy of egg surface disinfectants in captive spawning Atlantic cod Gadus morhua L. and haddock Melanogrammus aeglefinus L.

In an effort to optimize the efficiency of high‐density incubation of Atlantic cod Gadus morhua and haddock Melanogrammus aeglefinus eggs, the per cent hatch of eggs treated with four disinfectants (3% hydrogen peroxide, 1% polyvinylpyrrolidone iodine, 0.1% sodium hypochlorite and a 0.005% antibiotic solution – penicillin/streptomycin) was compared in both species. The per cent hatch of eggs of each species was greatest after a 24 h treatment with the antibiotic solution. The hatching success of eggs treated within the different disinfectant treatments depended upon the embryonic developmental stage in both species. The sodium hypochlorite treatment had the lowest % coverage of colony growth after disinfected haddock eggs were plated onto sterile agar media, highest survival rates to the end of the embryonic period, but the lowest per cent hatch.     

Evaluation of Experimental and Practical Diets for Bluegill Lepomis macrochirus and Hybrid Bluegill L. cyanellus × L. macrochirus

Two experiments were conducted to identify appropriate experimental and practical diets for bluegill Lepomis macrochirus and hybrid bluegill L. cyanellus × L. macrochirus reared in aquaria. In the first study, four experimental diets and five commercial diets were evaluated in juvenile hybrid bluegill initially weighing 4.8 g/fish. The experimental diets contained casein (CAS), casein + gelatin (CAWGEL), casein + L‐arginine‐HCI (CAS/ARG), or casein + gelatin + crystalline amino acids (CAS/AA) as sources of crude protein. The commercial diets included three diets formulated to meet the nutritional requirements of rainbow trout Oncorhynchus mykiss and two diets formulated to meet the nutritional requirements of channel catfish Ictalurus punctatus. Each diet was fed twice daily at a rate of 4% of body weigh/d to triplicate groups of fish. At the end of the 8‐wk feeding trial, weight gain was significantly higher in fish fed the best commercial rainbow trout diets (205–217%) compared to fish fed diets formulated for channel catfish (87–104%). Weight gain and feed efficiency (FE) of fish fed the experimental diets (5346% and 0.19–0.32, respectively) were significantly lower than those of fish fed the commercial rainbow trout diets (143–217% and 0.49–0.64, respectively). In the second experiment, the same dietary treatments were fed for 8 wk to juvenile bluegill initially weighing 3.7 g/fish. Each diet was fed twice daily at a rate of 4% of body weight/d to triplicate groups of fish. Weight gain was significantly higher in fish fed commercial trout diets (291–402%) compared to fish fed diets formulated for channel catfish (164–191%). Weight gain and FE of fish fed CAS/ARG were significantly higher than those of fish fed the commercial catfish diets, but significantly lower than those of fish fed the best commercial trout diets. Results of this study indicate that commercial rainbow trout diets are preferable to commercial channel catfish diets for culture of bluegill and hybrid bluegill. More research is needed to identify appropriate experimental diets for this group of fishes.     

Sea-ranching of brown trout, Salmo trutta L.

Abstract  In total, 8211 1-year-old and 14839 2-year-old hatchery-reared brown trout, Salmo trutta L., from 11 stocks were released at the mouth of the River Imsa, southwestern Norway. The recapture rates and total estimated yield were higher for 2- than 1-year-old trout, although recapture rates varied between years of release and stocks. The recapture rate increased with mean individual weight at time of release. Total estimated yield from the individual groups of 1+ trout ranged from 2 to 20 kg per 1000 trout released and for 2+ trout between 11 and 250 kg per 1000 fish released. In all cases, yields were lower than the economic break-even yield. Most fish were recaptured the year of release (89.2% of 2+ and 76.2% of 1+ trout). Almost 31% of the recaptures were caught at sea and 69% in fresh water; 95.8% of the latter were taken in the River Imsa trap.     

Eggs of gilthead seabream Sparus aurata L. as a potential enrichment product of Brachionus sp. in the larval rearing of gilthead seabream Sparus aurata L.

The gilthead seabream Sparus aurata L. is a sequential spawner whose reproductive cycle can be manipulated to obtain year-round egg and fry production. Hence, there is an overproduction of eggs in commercial hatcheries that is normally wasted. Two feeding experiments were conducted with the purpose of investigating the potential use of fresh and freeze-dried gilthead seabream eggs for the enrichment of live preys. The first experiment was also designed to study the possibility of using freeze-drying as a conservation process for eggs in excess. Larvae were reared for 20 days after hatching (DAH),on a diet of Brachionus sp. As experimental controls, the commercial enrichment emulsion SUPER HUFA was used in the first experiment, and the microalgae Nannochloropsis sp. in the second. This study demonstrated the potential of gilthead seabream eggs as an enrichment product to be used in the feeding of the first larval stages of Sparus aurata L. The data obtained emphasize the need to have an overall perspective of the nutritional requirements of the organisms in culture.     

Artificial insemination in tench, Tinca tinca L.

Abstract. The sperm of tench, Tinca tinca L., is characterized by a milky colour and consistency, and is of very low density. After collecting the sperm, motion of spermatozoa was recorded even without water activation. A better motility value (value 4·36 on average) was observed in spermatozoa collected in immobilizing solution (collecting medium) and stored for 3h, when compared with spermatozoa without collecting medium. Average total and relative numbers of spermatozoa were 12·16 × 10⁹ per male and 18·50 × 10⁹ per kg of body weight, respectively. When testing the effect of activating solution in artificial propagation of tench, the highest fertilization rates (81·3 and 85% in two cases) were found for NaCl solution with an osmotic concentration of 34 or 69 mOsmol and for fresh water, respectively. The fertility rate was reduced significantly ( P < 0·01) by any increase above 105 mOsmol in NaCl concentration in the activating solution. In the tests of optimal method of artificial fertilization, the highest hatching rate of sac fry (71·35%) was found in sperm collected into immobilizing solution. The application of immobilizing solution significantly increased the number of sac fry at the levels P < 0·1 and P < 0·01, if compared with intact sperm stored for 3 h and fresh sperm, respectively.     

The pathology of Saprolegnia infections of Anguilla anguilla L. elvers

Abstract. The clinical signs and histopathology of Saprolegnia sp. [related to S. diclina Humphrey (syn. S . parasitica Coker)] are described in cultured Anguilla anguilla L. elvers under an intensive production system. The main lesions observed were loss of epithelium leading to ulceration, oedema and myofibrillar degenerative changes of the muscle mass. The oedema resulted in swelling of the inter-myotomal connective tissue, loss of nuclei and minor host reaction. Traumatic lesions with subsequent bacterial infections had a mononuclear inflammatory response. It is suggested that the rapid extension of the lesion is due to the loss of integrity of the integument and the widespread oedema, which altered the viability of tissues and assisted the Saprolegnia infection. The condition was fatal for infected elvers.     

Cryopreservation of sperm of common carp, Cyprinus carpio L.

Milt of common carp, Cyprinus carpio L. was cryopreserved in pellet form with the use of 12 extenders. Most efficient were: BE2 original extender (containing 85 mM NaCl, 50 mM KCl, 3 mm CaCl₂, 1 mm MgCl₂ with 10% dimethyl-acetamide (DMA) and 10% addition of hen's egg yolk) and Kurokura et al.'s extender with 15% DMA and 10% yolk (about 73% and 69% of eyed eggs, about 61% and 52% of swim-up larvae, respectively). Within the most effective treatments, survival from the eyed-egg stage to the swim-up stage was similar to that observed in the control group. Survival from the eyed-egg stage to the swim-up stage (percentage of eyed eggs was considered as 100%) was highly significantly and positively correlated with the actual rate of swim-up larvae.     

Pathology of Enterococcus sp. infection in farmed turbot, Scophthalmus maximus L.

Abstract The lesions of an enterococcal septicaemia occurring in turbot, Scophthalmus maximus (L.), cultured in several farms in northwest Spain are described. The agent of this septicaemia was identified previously as an Enterococcus -like bacterium. Two main patterns of lesions were observed in the diseased turbot: a focal form characterized by exophthalmia, muscular haemorrhages, acute branchitis, and suppurative inflammation of periorbital tissues, eyeball, meninges and brain; and another generalized form with similar lesions, but showing more extensive haemorrhages, ulceration and purulent inflammation of the skin, desquamative enteritis, and necrosis of spleen and kidney. Fatty changes of the liver were observed in all turbot examined (diseased and controls), which indicates that these alterations were not related to the infection. Experimentally inoculated turbot developed lesions corresponding to the generalized form of the natural disease. Although the Enterococcus strain was recovered in pure culture from all the organs, Gram-positive bacteria could not be visualized histologically in the lesions of muscle and brain.     

Serum lipoproteins in haddock, Melanogrammus aeglefinus L.

The lipoprotein and lipid composition of the serum in postabsorptive haddock was characterized. A low level of very low density lipoproteins (VLDL; <50 mg dL^?1) was observed in serum. High density lipoprotein (HDL) was the predominant lipoprotein class followed by low density lipoproteins (LDL). Of the lipoprotein classes, the highest proportions of triacylglycerol (28%) and phospholipid (64%) were observed in the lipid of VLDL and HDL, respectively. Serum lipid (48%), phospholipid (50%) cholesterol ester (65%) and HDL (51%) contained a high level of polyunsaturated FA, particularly eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Serum triacylglycerol (38%) and VLDL (36%) contained a lower proportion of polyunsaturated fatty acid. The phospholipid, triacylglycerol, cholesterol ester and cholesterol contents of the whole serum were 739, 214, 201 and 141 mg dL^?1 respectively. On the basis of total acyl carbon number, the 38C (36%) and 36C (24%) molecules were the predominant phospholipids. The 50C (11%), 52C (17%), 54C (21%), 56C (21%) and 58C (15%) molecules were the major triacylglycerols. High molecular weight apo B‐like proteins were observed in the VLDL, LDL and intermediate density lipoprotein (IDL) fractions. An apo AI‐like protein was predominant in the HDL fraction. The prevalence of enlarged fatty livers in cultured gadoid fish (i.e. haddock and cod) is a major constraint to their commercialization and has been associated with the level of dietary lipid. Information on lipid (triacylglycerol) transport out of the liver through the serum as lipoproteins (VLDL) has implications for our understanding of fatty liver development in cultured gadoid fish. The low level of VLDL triacylglycerol (<12 mg dL^?1) circulating in the serum of postabsorptive haddock suggests either a low level of lipid transport out of the liver as triacylglycerol or relatively rapid turn over of VLDL.