Growth, osmoregulation and sexual maturation of underyearling Atlantic salmon smolt Salmo salar L. exposed to different intensities of continuous light in sea cages

Atlantic salmon smolts are usually transferred to sea water during early spring, but photoperiod treatment can be used to produce underyearling (0+) smolts for transfer to sea water in late autumn, 7–8 months earlier than usual. This study investigated the effect of exposure to additional continuous light (LL) of different intensities on 0+ smolts after transfer to sea water. 0+ smolts transferred to sea cages in mid-October were exposed to natural light (NL) or LL of one of three intensities (low, medium or high) until January, whereupon they experienced NL until harvest in December. Fish in all groups displayed a normal ability to hypoosmoregulate, assessed by monitoring plasma chloride concentrations after transfer to sea water. No consistent differences in length, weight or condition were found between LL groups. The LL groups had greater growth in length than the NL group during the time of LL exposure, followed by an increase in weight when exposed to NL. This resulted in fish of larger size than the NL group. By August, the fish in the NL group had caught up with the LL groups in respect of length, weight and condition factors. This suggests that the LL treatment led to increased winter growth and phase-shifted a seasonal pattern of growth. The incidence of sexual maturation was low (< 1%), with no differences between groups.     

Production of meiotic gynogenetic and triploid sea bass, Dicentrarchus labrax L.: 1. Performances, maturation and carcass quality

Meiotic gynogenetic and triploid sea bass were produced by pressure shocks according to a previously published protocol. Pressure-treated groups did not survive as well as controls during early development and larval rearing. Performances, sexual maturation and carcass quality were examined over a period of 34–45 months. At the age of 34 months, growth of the gynogenetic fish was comparable to that of the control but inferior in the triploid fish. A predominance of male fish was found within the triploid groups, while diploid and meiotic gynogenetic fish showed equal proportions of the sexes. Gonadal maturation in triploid fish was significantly impaired, particularly in the females that showed rudimentary ovaries. Triploid males exhibited primary maturation but proved to be gametically sterile. Pressure-induced triploids did not grow as well as diploids, but these results might be ascribed to specific on-growing conditions (communal rearing). The performance of gynogenetic sea bass was comparable to that of control. The superiority of diploid fish over their triploid counterparts was confirmed during the final growing period and more clearly so in females. Performances of triploids varied according to their maternal origin. Overall, striking qualitative differences between diploid and triploid fish were found at the age of 34 and 45 months, although the results varied in a gender-specific manner. A strong maternal effect was also observed. The potential advantages of triploid sea bass for aquaculture purposes are discussed.     

Delayed gametogenesis and spawning of sea bass (Dicentrarchus labrax L.) kept under different photoperiod and temperature regimes

The present work investigates the importance of day length and temperature in the control of reproduction of sea bass, as well as the effectiveness of LHRHa and HCG in inducing spawning out of season in this species. A controlled regime was produced and seasonal cycles with high components of temperature and photoperiod were extended from the summer solstice for at least 6 months, followed by a short photoperiod regime for 3 months before a new increase in these components. Natural spawning in the control fish occurred more frequently in mid February, although it was also observed in January and early March. Temperature manipulation delayed the spawning one month with respect to the controls, although some of the animals entered into gonadal regression. Photoperiodic manipulation delayed maturation for three months with respect to controls but it was necessary to perform hormonal induction of spawning. Although LHRHa and HCG were both applied, only intraperitoneal injections of LHRHa were effective in inducing spawning of sea bass out of season when the temperatures were 17°C. Dephasing between the annual changes in photoperiod in relation to the coordination of the different events of the sexual cycle of sea bass is considered.     

Oocyte Development and Induced Spawning of Smallmouth Bass (Micropterus dolomieui) in Response to Photoperiod and Temperature Manipulation: Preliminary Results

Smallmouth bass ( Micropierus dolomieui ) in Quebec spawn between the end of May and mid-June. Wild broodstock (4 to 8 years old) and laboratory-reared ones (0+ years old) reared in a water recycling system were submitted to different temperature and photoperiod regimes to extend their natural spawning period. Oocyte maturation followed in vivo showed that oocytes developed to stage III in both cases but final maturation and ovulation was limited to the laboratory-reared bass and this, a month before the normal spawning period, at 20.5 cm TL. Exogenous factors are examined, specifically duration of long photoperiod and vital space related to non-spawning of wild broodstock.     

Testosterone-mediated complete feminization with precocious ovarian maturation in catfish, Heteropneustes fossilis (Bloch)

The spawning period of Indian catfish, Heteropneustes fossilis (Bloch), was hormonally manipulated by testosterone treatment of hatchlings for one month. Immersion treatment of testosterone propionate at 300 μg L¹ water resulted in complete paradoxical feminization, with about 70% of females showing precocious ovarian maturation 3 months ahead of spawning season.     

Protein sparing effect of dietary lipids in common dentex (Dentex dentex): A comparative study with sea bream (Sparus aurata) and sea bass (Dicentrarchus labrax)

The common dentex (Dentex dentex) is a sparid fish which is considered a suitable candidate for Mediterranean aqua-culture. A seven-weeks feeding trial was conducted over the summer period with common dentex, sea bream (Sparus aurata) and sea bass (Dicentrarchus labrax). All three species were fed to visual satiety with two practical diets with varying crude protein and crude fat levels (55 % protein, 9 % lipids; 46 % protein, 17 % lipids). The initial body weights were 8.2, 11.6 and 17.3 g for common dentex, sea bass and sea bream, respectively. In all cases, specific growth rates were not significantly affected by dietary treatment, but they varied among species (sea bass 1.7–1.8 %; sea bream 2.1–2.3 %; common dentex 3.1–3.2 %). When comparisons between fish species were made, we observed that the increase in growth rates was linked to a decrease of the whole body fat content, as a consequence of a greater utilisation of dietary lipids as energy substrates. Furthermore, in common dentex, the 17 % lipid diet was able to improve protein retention, but this diet effect was less significant in sea bream and sea bass. In contrast to sea bream, the 17 % lipid diet did not up-regulate plasma GH levels in common dentex, which provides additional evidence for a more efficient utilisation of dietary lipids.     

流水槽和池塘两种养殖模式下大口黑鲈存活率、生长和性腺成熟的比较研究

通过比较大口黑鲈(Micropterus salmoides)在流水槽-池塘接力养殖和池塘养殖两种模式中的存活率、生长、性腺成熟、饵料系数的差异,以探索大口黑鲈流水槽-池塘接力养殖新模式的可行性.在8月初将大口黑鲈鱼苗(初始平均体重为23.933 g)分别放养于池塘和水槽中养殖,并于次年4月份将流水槽养殖的大口黑鲈转入...     

Response to individual selection for age at sexual maturity in Atlantic salmon

Atlantic salmon (Salmo salar) that mature sexually at 1 year of age (as parr or precocious males), at 4 years of age (after two winters in the sea) and at 5 years of age (after three winters in the sea) were used to study response to individual selection for age at sexual maturity. Six mating groups were made: between fish of the same age (4 × 4 and 5 × 5); reciprocal matings between 4- and 5-year-old fish (4 × 5 and 5 × 4); and matings between 1-year-old precocious males and 4- and 5-year-old females (1 × 4 and 1 × 5). Parental age at sexual maturity was found to influence markedly the offspring age at sexual maturity. The heritability for age at maturity in the sea was estimated at 0.48 ± 0.20 from the offspring—dam regression. It is concluded that there is considerable opportunity to alter the age at sexual maturity in Atlantic salmon through selection. Evidence was found that maturation of parr is a heritable trait and that it is independently inherited from maturation in the sea.     

Growth performances for monoculture and polyculture of hatchery‐reared juvenile spotted babylon,Babylonia areolata Link, 1807, in large‐scale earthen ponds

This study was conducted to determine the feasibility of growing out hatchery‐reared spotted babylon juvenile (Babylonia areolata) in earthen ponds. The growth, survival and water quality for monoculture of spotted babylon were compared with the two polyculture trials with sea bass (Lates calcarifer) or milkfish (Chanos chanos). This study provided good results for growth and survival of spotted babylon in earthen ponds. The mean body weight gain of snails held in the monoculture was 5.39±0.08 g, and 4.07±0.16 and 4.25±0.11 g for those held in the polyculture with sea bass or milkfish respectively. Food conversion ratios (FCR) were 2.69, 2.96 and 2.71 for snails held in the monoculture and polyculture with sea bass and milkfish, respectively, and the final survival rates were 84.94%, 74.30% and 81.20% respectively. There were no significant differences in each parameter of water quality among the treatments but significant differences among the culture period were present (P<0.05). Salinity and total alkalinity showed the greatest changes during the culture period for all treatments. Seawater temperature, pH, dissolved oxygen, nitrite–nitrogen and ammonia–nitrogen gradually changed over the culture period for all the treatments. The present study indicated the technical feasibility for monoculture and polyculture of B. areolata to marketable sizes in earthen ponds.     

Effects of dietary protein and lipid levels on growth performance and body composition of black sea bass Centropristis striata (Linnaeus 1758) during grow-out in a pilot-scale marine recirculating system

The influence of four formulated practical diets, with different protein and lipid levels, on the growth and body composition of black sea bass ( Centropristis striata L.) pre-adults was evaluated in a pilot-scale marine recirculating system. Four test diets were prepared with a combination of two protein levels (44% and 54%) and two lipid levels (10% and 15%). The diets were as follows: low protein and low lipid (LP:LL; 44:10), low protein and high lipid (LP:HL; 44:15), high protein and low lipid (HP:LL; 54:10) and high protein and high lipid (HP:HL; 54:15). Fish (mean weight=75.5 g) were fed the respective diets for 90 days. For fish fed LP:HL, body weight gain was significantly ( P <0.05) higher than fish fed LP:LL. Increasing the protein level from 44% to 54% did not produce a significant effect on weight gain at high lipid level. A significant ( P <0.01) interactive effect between dietary protein and lipid levels on the growth and feed utilization was observed. Total lipid content in the whole body, muscle and liver was significantly affected by the dietary lipid levels. The results suggested that a combination of 44% dietary protein and 15% lipid was optimal for the growth of black sea bass.     

Early growth and reproduction of hatchery-produced Pacific oyster Crassostrea gigas in Gamakman Bay off the southern coast of Korea

We investigated the early growth and reproduction of hatchery-produced Pacific oysters Crassostrea gigas raised in a suspended long-line facility in Gamakman Bay, off the south coast of Korea. In October 2009, 4?months after transplanting, shell length had increased from 27.4 (July) to 82.5?mm (October), and tissue weight had increased from 0.2 to 5.2?g, indicating that the oyster had reached a marketable size in this month. Histological studies indicated rapid gonad maturation, and the oysters spawned during August and October, with a peak in September. An enzyme-linked immunosorbent assay used to quantify egg biomass revealed that the oysters produced a relatively small quantity of eggs, ranging from 5.1?% (August) to 8.8?% (September) of their body weight. The low total carbohydrate reserve in the tissue recorded in August and September coincided with intense energy utilization due to spawning, while the protein maximum in September matched peak egg mass. Our results suggest that hatchery-produced seed could supply a portion of the spat required in Gamakman Bay as well as in other oyster culture grounds of Korea, where the oyster industry is facing a shortage in the supply of natural spat.     

Effect of low temperature rearing, using deep-sea water, on gonadal maturation of the short-spined sea urchin, Strongylocentrotus intermedius, in Rausu, Hokkaido

It has long been hoped that sea urchins could be served to visitors to seafood restaurants, hotels, and summer festivals in Rausu, located in the world natural heritage site ??Shiretoko,?? during the summer tourist season. However, to date this has not been feasible because of the sea urchin spawning season (July?CSeptember), during which the quality of the gonads, the edible part of the sea urchin, decreases due to maturation. In this study, we examined the possibility of suppressing gonadal maturation and maintaining high-quality sea urchin gonads by low-temperature rearing using deep-sea water. Unripe sea urchins captured before the spawning season were reared under two temperature conditions from June to September. In those groups reared at ambient temperatures (2.8?C19.6?°C), gametogenesis in both sexes progressed rapidly with increased temperature, and almost all sea urchins reached full maturity by late July. In contrast, in groups reared at low temperatures (2.1?C5.1?°C), gametogenesis progressed slowly and >60?% of the sea urchins did not reach maturity even by early September. The feeding experiment also revealed that feeding with live Saccharina diabolica could increase the gonadal volume efficiently under low-temperature rearing conditions. These results demonstrate that low-temperature rearing, supplemented with feeding, is effective in suppressing gametogenesis to allow for the harvesting of high-quality sea urchins during the summer tourist season.     

6-姜酚协同超高压处理对花鲈挥发性成分的影响

为揭示6-姜酚浸泡协同超高压处理对花鲈挥发性成分的影响,及时掌握鱼肉品质变化情况。采用电子鼻和顶空固相微萃取-气相色谱质谱联用CHS-SPME-GC-MS技术研究了浓度为8μg/m L的6-姜酚浸泡协同超高压处理(200 MPa)的花鲈和对照组(空白、8μg/m L 6-姜酚浸泡、200 MPa处理)品质及挥发性成分的变化。分析了处理组和对照组花鲈样品的色泽、质构特性及挥发性成分的变化。结果表明,6-姜酚浸泡协同超高压处理比6-姜酚浸泡、200 MPa处理及未处理的效果显著,有效改善了花鲈色泽及质构特性。电子鼻能够较好区分不同处理方式下花鲈的风味;主成分分析显示各个样品间差异明显,电子鼻区分度良好。采用气-质联用技术分析表明,花鲈在不同处理方式下的挥发性成分发生明显变化。主要挥发性物质有醇、醛、酮、酸、酯、烃、芳香族和含氮化合物等。在空白组、6-姜酚浸泡、200 MPa处理和6-姜酚浸泡+200 MPa处理的鱼肉中分别检测出43、40、49及30种主要的挥发性物质,这些挥发性物质的结合,形成了各自的风味特征,决定了不同处理方式下花鲈肉风味的差异。     

Differentiation of gonad maturation in sibling precocious males of the sea trout (Salmo trutta m. trutta L.) in their first year of life

Age at maturity and dynamics of gonadal cycle vary among individuals in a standard population; the extent of that variability in a group of siblings is not known for any species. Therefore, the aim of the study was to find out how the differentiation of gonad development varies in a group of sibling fish. The study involved 176 seven-month-old sea trout parr (mean fork length of 11 cm) collected at a single time point during their first spawning season (late October) from the brook of Pniewa in Western Pomerania (Poland). Gonad maturation was determined from histological analysis which was interpreted according to specially developed criteria.

The stage and forms of gonad maturation were diverse in the sibling group studied. Gonads of 52.8% males were not maturing (Class I), with only spermatogonia A present. The remaining males (47.2%) had gonads differing widely in the development, from beginning of maturation to completion of the reproductive cycle (Classes from II to VIII). In addition to the classes described, some males were observed to feature attempted maturation. It is difficult to provide an unequivocal estimate of the proportion of precocious males (mature at a young age, prior to the first descent to the sea) in the first year of life because of difficulties in categorizing males in Class II. It was predicted that 32.4% of the population would complete the cycle during the first spawning season. The body length and weight of the maturing males was significantly smaller (P < 0.05) than that of the non-maturing males.

Three forms of gonad maturation were identified. Gonads of a large group of precocious males (70%) developed incompletely (only some germ cell developed during the reproductive cycle), some of those gonads assumed the form of attempted maturation and partial maturation. Testes of the remaining 30% of the males underwent complete maturation. Gonads that undergo attempted maturation do not spermiate.

It is only from microscope-aided analysis of the testes that the class of gonad development can be accurately evaluated and the extent of precocious maturation assessed, particularly in fish maturing for the first time. It is impossible to correctly identify maturing males of the underyearling sea trout on the basis of morphological examination of gonad appearance, abdominal massage to detect spermiation or gonadosomatic index value.     

Growth trials for polyculture of hatchery-reared juvenile spotted babylon (Babylonia areolata) and sea bass (Lates calcarifer) in a flow-through sea water system

Juvenile spotted babylon (Babylonia areolata) and sea bass (Lates calcarifer) were cultured in 11.5‐m³ indoor rearing tanks supplied with flow‐through of ambient natural sea water over a 120‐day experiment. Each species, stocked at the following densities for the following treatments, was tested with three replicates per treatment: 5000 B. areolata per tank (Treatment 1); 200 L. calcarifer per tank (Treatment 2); and 5000 B. areolata plus 200 L. calcarifer per tank (Treatment 3),. The average growth (length and weight), feed conversion ratio and total production of spotted babylon and sea bass from Treatment 3 were not significantly different from those of Treatment 1 and 2 (P > 0.05). Average survival rates for both spotted babylon and sea bass exceeded 95% for all treatments.     

Physiological stress and innate immune response in gilthead sea bream (<Emphasis Type="Italic">Sparus aurata)</Emphasis> and sea bass (<Emphasis Type="Italic">Dicentrarchus labrax</Emphasis>) exposed to combination of trimethoprim and sulfamethoxazole (TMP-SMX)

The purpose of this study was to determine whether gilthead sea bream and sea bass treated with combination of trimethoprim and sulfamethoxazole (TMP-SMX) differed in terms of physiological and innate immune biomarkers. Fish were exposed to TMP-SMX at 40 ppm concentration for 1 h as a prophylactic usage. Plasma cortisol, glucose, electrolytes (Ca, P, Na, K, Cl, and Mg) as well as plasma lysozyme activity, C-reactive protein (CRP), and ceruloplasmin (Cp) were measured soon after treatment and following 24 and 48 h in normal sea water for recovery. Treatment with TMP-SMX in both gilthead sea bream and sea bass led to an increase in plasma cortisol and glucose. Fluctuations in some electrolytes were found after treatment and during recovery period, however, the ratios of monovalent ions in treated sea bream were similar to control. Hematocrit values as well as plasma lysozyme activity in gilthead sea bream and sea bass were not affected by the treatment. CRP in gilthead sea bream and Cp in sea bass responded to the treatment with decreased levels. Both gilthead sea bream and sea bass displayed a rapid physiological stress response and sensitivity to TMP-SMX exposure, which requires more than 48-h period for regaining homeostasis.     

Application of systematic adaptive cluster sampling for the assessment of black sea bass <Emphasis Type="Italic">Centropristis striata</Emphasis> abundance

In this study, we applied systematic adaptive cluster sampling (SACS) to assess the abundance of black sea bass Centropristis striata on hard bottom habitats in the Mid-Atlantic Bight (MBA; USA). We used a remote underwater video system to obtain video recordings of black sea bass from 25 June to 6 August 2013 within a 25-square nautical mile (nmi²) sampling region. Data in the form of fish counts were collected from video recordings and used to estimate parameters including sample means and population totals of black sea bass for two adaptive cluster sampling estimators and a single systematic sampling estimator. The precision and relative efficiencies of the parameter estimates were also calculated and compared. In total, two adaptive cluster samples were encountered within the sampling region. Sample means and population totals were largest for the systematic sampling (SS) estimator while the adaptive sampling estimators produced parameter estimates with the lowest variances and highest precision. Our results indicated that SACS was more efficient and advantageous with respect to sampling costs [i.e., sampling time (hours) and travel distance (kilometers)] than SS alone for assessing the abundance of clustered populations of C. striata on hard bottom habitats in the MBA.     

Photoperiodic manipulations of the reproductive cycle of sea bass (Dicentrarchus labrax) and their effects on gonadal development, and plasma 17ß-estradiol and vitellogenin levels

The annual profile of plasma vitellogenin (VTG) and 17ß-estradiol (E₂) levels, as well as gonadal development and spawning characteristics were investigated in captive female sea bass (Dicentrarchus labrax). Endocrine and gonadal changes were studied in fish reared under natural conditions or exposed to manipulated photothermal cycles. In natural conditions of photoperiod and temperature, sea bass spawned from February through March (East coast of Spain, 40°N 0°E). One or two months of constant long-days (15L/9D) in a constant short-day photoperiod regime (9L/15D) all-year-round, given early in the year (March and March–April), advanced spawning by 3 months. The same treatment applied later in the year (September–October) delayed spawning by 1 month, compared to controls.In all groups, changes in plasma VTG levels were correlated with E₂ levels, oocyte growth and spawning time. In control females, VTG was low (<100 ng ml^-1) during the summer, until its first surge in plasma 4 months before the beginning of spawning. The VTG (3.1 ± 0.3 mg ml^-1) and E₂ (4.1 ± 0.5 ng ml^-1) levels showed a single annual peak during late vitellogenesis, the time of the highest proportion of vitellogenic oocytes in the ovary. Constant high levels of VTG (1–1.4 mg ml^-1) and E₂ (1.6–1.9ng ml^-1) were maintained during the entire spawning time, together with the presence of vitellogenic oocytes, suggesting the existence of several waves of oocyte growth in the ovary and thus, several spawns per female. Endocrine profiles and oocyte development in fish exposed to constant photoperiods were similar to controls, but were shifted in time in relation to the displacement of the spawning time. In the fish showing advanced spawns, the duration of the gametogenic proces was compressed when compared to controls. The differences observed in the evolution of the reproductive-related factors in the advanced groups, which were exposed to a reduction in temperature to 15°C, suggest an influence of the temperature in the early stages of the reproductive cycle in sea bass.     

Fertilization strategies for Sea Bass Dicentrarchus labrax (Linnaeus, 1758): effects of pre‐incubation and duration of egg receptivity in seawater

Studying gamete biology can provide important information about a species fertilization strategy as well as their reproductive ecology. Currently, there is a lack of knowledge about how long sea bass Dicentrarchus labrax eggs can remain viable after being activated in seawater. The objectives of this study were to understand the effects of pre‐incubation of fresh and overripe sea bass eggs in seawater and to determine the duration of egg receptivity. Pooled eggs (fresh and overripe) from four females were pre‐incubated in seawater for 0 min (control), 0.5 min, 1 min, 3 min, 10 min and 30 min and then fertilized by pooled sperm from four males. The fresh eggs had a higher fertilization success than overripe eggs. Our results revealed a significant effect of pre‐incubation time for both the fresh (P < 0.01) and overripe eggs (P < 0.01). Fertilization success of eggs significantly declined for both these treatments after 3 min of pre‐incubation, which clearly indicates that sea bass eggs are able to be fertilized by sperm for up to 3 min after release into seawater. This study has particular importance for understanding fertilization strategies, reproductive potential, as well as reproductive ecology of sea bass.     

欧洲舌齿鲈和花鲈生长期营养需求特点综述

鱼类的生长期(幼鱼和成鱼阶段)相对于仔稚鱼阶段在养殖生产中持续时间较长,是养殖生产的重要阶段和保证产品质量的关键时期。鱼类生长期饲料使用量大、所占养殖成本高。该时期营养需求特点不同于仔稚鱼期和亲鱼期,有其阶段特殊性,因此,针对鱼类生长期营养需求特点的研究有其必要性。花鲈(Lateolabrax japonicus)作为我国的名优海水鱼,得到大规模养殖,市场广阔。欧洲舌齿鲈(Dicentrarchus labrax)作为引进新品种,与花鲈的生活习性、营养需求和生长特点颇为相似。在现有文献基础上,较系统地综述和比较了欧洲舌齿鲈和花鲈对蛋白质、氨基酸、脂肪、脂肪酸、维生素、矿物质等营养物质的需求量范围和需求异同点,并提出了今后的研究方向和重点,以期为专用配合饲料研发、更好地满足养殖生产提供参考。