Graded environmental hypercapnia in juvenile spotted wolffish (Anarhichas minor Olafsen): effects on growth, food conversion efficiency and nephrocalcinosis

Growth performance and food conversion efficiency (FCE) were investigated in juvenile spotted wolffish (Anarhichas minor Olafsen), mean (S.D.) initial weight 15.7 (4.8) g, reared at four levels of carbon dioxide (CO_2(aq)) for 10 weeks at 6 °C and 33‰. CO₂ levels averaged 1.1 (control), 18.1 (low), 33.5 (medium) and 59.4 (high) mg l⁻¹, with corresponding pH values of 8.10, 6.98, 6.71 and 6.45, respectively. In addition, kidneys from sampled fish were examined macroscopically for gross signs of calcareous deposits, i.e. nephrocalcinosis, at the start and end of the experiment. Growth was significantly reduced at the highest concentration (P<0.0001), as compared to all other groups, while no overall differences in growth rate or mean weight were seen in the range of 1.1–33.5 mg CO₂ l⁻¹ at the end of the experiment. Daily feeding rates and total food consumption were reduced at the highest concentration (P<0.001), whereas food conversion efficiency did not vary significantly between groups. Plasma chloride levels displayed a significant decrease with increasing CO₂ levels, from 151.3 mmol l⁻¹ (1.1 mg CO₂ l⁻¹) to 128.3 mmol l⁻¹ (59.4 mg CO₂ l⁻¹) at the end of the experiment, whereas plasma osmolality in the high CO₂ group was significantly higher compared to the control group at the end of the experiment (371.4 and 350.8 mOsmol kg⁻¹, respectively). Nephrocalcinosis was observed in all groups at the end of the experiment, but was most pronounced in the medium and high CO₂ group.     

盐度对杂交石斑鱼受精卵孵化和卵黄囊仔鱼形态及活力的影响

为了研究盐度对褐点石斑鱼(Epinephelus fuscoguttatus)♀×清水石斑鱼(Epinephelus polyphekadion)♂杂交后代(简称杂交石斑鱼)受精卵孵化、卵黄囊仔鱼形态及活力的影响,将杂交石斑鱼受精卵置于不同盐度水体中,观察盐度胁迫下卵径、油球径、孵化率及畸形率,以及孵化后卵黄囊仔鱼形态变化和活力状况。结果表明,在本研究条件下,受精卵卵径随盐度降低而增大,油球径不随盐度变化而变化。在盐度18~36范围内均能孵化仔鱼,但因盐度不同孵化率和初孵仔鱼畸形率有显著差异(P0.05);随盐度升高,孵化率呈先升后降的变化,初孵仔鱼畸形率则相反。盐度24~36组孵化后3 d仔鱼卵黄囊几乎完全消耗,组间无显著差异(P0.05)。在盐度24~36范围内,随着盐度的增加,仔鱼的不投饵存活系数(SAI值)呈先升后降的变化曲线;盐度30~33范围内,初孵仔鱼SAI值大于5;5日龄仔鱼全部死亡,半数死亡时间出现在孵化后3.5 d。综上分析表明,该杂交石斑鱼受精卵孵化及仔鱼培育的适宜盐度范围为24~36,最适盐度范围为30~33。     

Effect of rearing density on the growth and welfare indices of juvenile spotted wolffish,Anarhichas minor (Olafsen)

The goal of this study was to determine the optimal stocking density for rearing juvenile spotted wolffish, Anarhichas minor (Olafsen), at two different sizes and assess the welfare status in relation to density. No major growth impairment was observed, although smaller fish (50–100 g) were significantly affected by density during the 120 days of the experiment, with final mean weights of 119.6 ± 11.6, 118.0 ± 5.8 and 88.7 ± 0.6 g for initial rearing densities of 10, 20 and 40 kg m^?2 respectively. No effect of rearing density was seen for larger fish (100–160 g) during the 90 days of the experiment, with final mean weights of 160.2 ± 5.9, 159.7 ± 3.7 and 163.7 ± 11.5 g at fixed rearing densities of 20, 30 and 40 kg m^?2 respectively. Our results suggest that the optimal rearing density of juvenile spotted wolffish is below 40 kg m^?2 for smaller size fish (～50–100 g) and probably ≥40 kg m^?2 for the larger fish (100–160 g). Furthermore, it appears that the range of rearing density used did not have a significant effect on a selection of stress indicators (Na⁺ and K⁺ concentration, haematocrit, hepatosomatic index, total amount of plasma proteins and liver and muscle water content) and immunity response (plasma lysozyme activity) of juvenile spotted wolffish, making it a very tolerant species to crowding.     

Growth and survival of first-feeding spotted wolffish (Anarhichas minor Olafsen) at various temperature regimes

In order to define temperature regimes that could benefit successful production of spotted wolffish (Anarhichas minor) juveniles, experiments with offspring from two different females were carried out. The larvae were fed a new formulated feed or a commercial start‐feed for marine fish, both of which have given high survival rates. In the first experiment newly hatched larvae were fed at constant 6 °C, 8 °C, 10 °C and 12 °C as well as at ambient seawater temperature (2.9–4.5 °C) during 63 days. High survival, 90% to 96%, was registered at ambient and most constant temperature regimes, whereas in the 12 °C groups survival was reduced to 80%. Growth rate (SGR) was very low, 1.8% day^?1, at the low ambient temperatures. Growth rate was positively correlated with temperature and varied between 3.1% day^?1 to 4.7% day^?1, from 6 °C to 12 °C. In the second experiment, set up to include potential detrimental temperatures and study beneficial effects of a more restricted, elevated first‐feeding temperature regime, the larvae were fed at constant 8 °C, 10 °C, 12 °C, 14 °C and 16 °C until 30 days post hatch, followed by constant 8 °C for the next 33 days. In this experiment, low survival, 25% and 2.0%, was registered at 63 days post hatch when larvae were reared initially at 14 °C and 16 °C respectively. The survival of the larvae at the other temperature regimes varied from 47% to 64%, highest survival rate (64%) was found at 8 °C. The lowest specific growth rate, 2.6% day^?1, was noted in the 16 °C group. At constant 8 °C to 14 °C (regulated to 8 °C), the SGR varied from 4.45% day^?1 to 5.13% day^?1. The larvae grew faster in the experiment when initially comparable temperatures (8 °C, 10 °C and 12 °C) were regulated to constant 8 °C after 30 days compared with the first experiment where feeding was carried out at the same constant temperatures (8 °C, 10 °C and 12 °C) during the whole experimental period.     

Metabolic and digestive enzyme activity profiles of newly hatched spotted wolffish (Anarhichas minor Olafsen): effect of temperature

Three groups of newly hatched spotted wolffish (Anarhichas minor) were held at three different temperatures in order to determine relationships between metabolic, digestive and growth response in rapidly developing larvae. Growth rates were successfully modulated by temperature (5, 8 and 12 °C). Activity levels of trypsin and lactate dehydrogenase (LDH) were positively linked to specific growth rates at all temperatures. Trypsin showed a positive compensation (higher activity at lower temperature) whereas glycolytic enzymes (pyruvate kinase and Lactate dehydrogenase) and aspartate aminotransferase (AST) showed a negative compensation (lower activity at lower temperature). Citrate synthase was not affected by growth rate, indicating that the level of aerobic capacity was adequate in sustaining the high energetic needs associated with rapid growth early in the life of the spotted wolffish. In light of our results, it is suggested that protein digestion, as demonstrated by the activity profile of trypsin in relation to growth rate and temperature, is likely a key growth‐limiting agent during the early‐life stages of wolffishes. Our results are discussed in comparison with A. lupus, a closely related species displaying different temperature preferences and growth capacities.     

The influence of rearing temperature on early development and growth of spotted wolffish Anarhichas minor (Olafsen)

Temperature influenced the developmental rate, survival and early growth of eggs and embryos of spotted wolffish, Anarhichas minor (Olafsen), an interesting candidate for cold water cultivation. The total incubation period decreased from 220 days at 4 °C (880 daydegrees), to 177 days at 6 °C (1062 daydegrees) and 150 days at 8 °C (1200 daydegrees) in these experiments. The proportion of normal embryos and survival of eggs until hatching were highest when the eggs were incubated at 6 °C. During the incubation period, the embryo and yolk sac size at 280 daydegrees was not significantly different but at 850 daydegrees the embryo size was inversely related to temperature and the remaining yolk sac size positively correlated with the incubation temperature. The transformation of yolk to body mass during incubation appeared to be most efficient at 4 °C, and the embryos hatched with a larger visible yolk sac at 6 and 8 °C. The largest larvae (wet‐weight) hatched from the largest eggs and the egg groups incubated at the lowest temperature (4 °C). There was no effect of temperature on meristic characters. During 6 weeks post‐hatching, all larvae from the three temperature groups were fed formulated dry feed in excess at 8 °C in low water‐level raceway systems. During startfeeding, the larvae from eggs incubated at the lowest temperature (4 °C) showed the highest growth rates (SGR). Best survival of larvae was noted among batches incubated at 6 °C.     

三丁基锡对褐菖鲉胚胎卵黄囊吸收的影响

鱼类胚胎期的营养对各种器官的发育至关重要,环境条件对营养吸收的影响会增加畸形率和死亡率。研究三丁基锡(tributyltin,TBT)对鱼类胚胎期营养吸收的影响有助于深入认识TBT对鱼类胚胎发育的毒性。本实验以海洋经济鱼类褐菖鲉(Sebastiscus marmoratus)为对象,研究环境水平TBT(0.01、0.1、1、10 ng.L-1)对胚胎卵黄囊吸收的影响。通过油红O染色,发现TBT暴露引起褐菖鲉胚胎血管系统中脂类染色信号减少,而卵黄中的脂类染色正常,说明TBT可能影响了胚胎正常血液循环,从而影响了正常的营养运输。另外,TBT对Na+,K+-ATP酶、碱性磷酸酶活性的抑制以及对甲状腺激素受体α和糖皮质激素受体基因表达的影响可能和其对卵黄囊的吸收抑制有关。TBT对鱼类胚胎卵黄吸收的抑制将影响鱼类的生长和发育,增加畸形率和死亡率,最终导致鱼类种群数量减少。     

池塘养殖鳗鲡初孵仔鳗生长发育和卵黄消耗的研究

本文初步研究了池塘养殖日本鳗鲡初孵仔鳗生长与卵黄消耗的关系。在水温(24±1)℃下,仔鳗发育至7~8日龄,口、肠道、肛门、胸鳍等器官形成。仔鳗全长与卵黄的关系为:(1)0~18 d仔鳗全长随日龄的增加而有不同程度的增长;其中0~7 d生长快,平均日增长0.57 mm/d,8~10 d,平均日增长0.13 mm/d,11~18 d,平均日增长0.09mm/d;(2)0~10 d,仔鳗以内源性营养方式吸收营养,仔鳗全长与卵黄消耗呈指数相关,可用公式Y=1.5879e1.4371L(R2=0.8979)表示,仔鳗卵黄消耗与日龄可用公式Y=0.0852e-0.5547L(R2=0.9702)表示;10 d后仔鳗卵黄消失。     

Ultrastructural pathology of Baltic salmon, Salmo salar L., yolk sac fry with the M74 syndrome

The ultrastructural pathology in liver, brain, skeletal and cardiac muscle of Baltic salmon yolk sac fry with the M74 syndrome is described. In the clinical stage of disease, the main pathological findings in the liver were a depletion of glycogen, condensation of nuclear chromatin, hydropic degeneration of mitochondria and a dilation of the bile canaliculi. In the terminal stage, additional findings were lipid accumulation and myelin whorls in the cytoplasm. The rough endoplasmic reticulum (RER) was degranulated and vesiculated and in some individuals, it formed concentric membranous whorls. Mitochondria showed several additional lesions, such as matrix densities, pleomorphism and cristae abnormalities. Skeletal myocytes were degenerated, and intracellular lipid accumulation was seen in the myocardium. In the brain, an increased frequency of cells exhibiting pyknosis or karryorhexis was recorded. The cytoplasm of these cells formed an amorphous mass of moderate density. The evaluation of brain and skeletal muscle was complicated by sporadic occurrence of pathological findings in the reference material, i.e. clinically healthy Baltic salmon yolk sac fry. As these yolk sac fry are suspected to have a subclinical thiamine deficiency, reference material in future studies should include salmon yolk sac fry from Atlantic populations or originating from reared broodstock.     

Population density,growth and reproduction of arapaima in an Amazonian river‐floodplain

Arantes CC, Castello L, Stewart DJ, Cetra M, Queiroz HL. Population density, growth and reproduction of arapaima in an Amazonian river‐floodplain. Ecology of Freshwater Fish 2010: 19: 455–465. © 2010 John Wiley & Sons A/S Abstract – Compensatory density effects are key features of fish population dynamics that remain poorly understood in tropical river‐floodplains. We investigated possible compensatory growth and reproductive processes for a river‐floodplain population of Arapaima sp., an extinction‐prone fish species of South America. Body growth was studied through analysis of ring patterns on the scales, and size and age at sexual maturity was studied through analysis of female gonads. Growth and maturity were compared for unmanaged conditions with relatively low population density (in 1990s) versus managed conditions with markedly higher density (in 2005–2006); between 1999 and 2005–2006, abundance increased 7.3 fold. Results contradict theoretical expectations for slower growth and delayed reproduction at higher population density. Total lengths of arapaima at low population density were significantly shorter for age classes 1–5 compared with lengths of those age classes at high population density (ancova , P < 0.0001 for both slopes and intercepts). Total length at 50% maturity (L₅₀) only declined about 4% with increasing density (e.g., 164 cm at low density vs. 157 cm at high density). Apparent faster growth at high density and only a slight change in size at maturity resulted in fishes spawning at an earlier age with high density conditions (age 3 vs. age 4–5). We hypothesise that these patterns reflect compliance with minimum size limits of catch during the high density (managed) situation, where there was no harvest of immature fishes. Compliance with minimum size limits, thus, may have led to faster average body growth rate and earlier reproduction, which has greatly promoted population recovery.     

Is batch variability in hatching time related to size heterogeneity and cannibalism in pikeperch (Sander lucioperca)?

Larval size heterogeneity is known to induce cannibalism, and procedures to avoid larval size differences are consequently implemented already during egg incubation and hatching. We investigated the relation between larval development variability, size heterogeneity and cannibalism in pikeperch. Larvae were sorted into five groups according to the time of hatching during a 65‐h period. The larvae with different times of hatch were then reared separately or together during an 18‐day period. Late hatched larvae were longer (P=0.003) and had less yolk remaining (P<0.001) than early hatched individuals at the time of hatching. However, on 11 days post fertilization, the late‐hatching larvae tended to have larger yolk reserves than earlier hatched individuals (P=0.07). Furthermore, the next day, a lower proportion in the late fraction had switched to exogenous feeding (P=0.024). That larvae with a late hatching time developed slower suggests a positive relationship between the hatching time and the embryonic developmental rate. However, differences in the length and available yolk reserves at hatching between larval fractions with different hatching times suggest that hatching is not strictly associated with a specific developmental stage, and that factors other than the development rate of the embryo are involved in the timing of hatching.