Tub gurnard Chelidonichthys lucerna L.: a new fish species suitable for farming? First answers evaluating the growth of juveniles reared at different stocking densities,welfare and fillet quality

A trial was conducted to evaluate the growth performance and survival of Chelidonichthys lucerna. A total of 13 352 180‐days old juveniles (5.5 ± 2 g; 5 ± 1 cm) were reared at two different densities (A‐EXP = 68 fish m^?3; B‐FFA = 15 fish m^?3) in eight tanks (four tanks per group) for 360 days. The welfare status and meat quality of fish were evaluated for the A‐EXP and B‐FFA groups in comparison with wild‐caught fishery gurnard (C‐WID). The survival rate was high for both A‐EXP (79%) and B‐FFA (93.5%). B‐FFA fish had the highest specific growth rate (1.16 vs. 1.07; P < 0.05), and were heavier than A‐EXP fish (321 ± 40 g vs .239 ± 44 g; P < 0.01). Rearing conditions did not affect blood metabolites, except for glucose concentrations, which were higher in C‐WID (P < 0.05). The meat quality traits showed that reared groups were fatter (2.8–3.2%) than C‐WID (0.94%); total n‐3 fatty acids (19.02–19.26%) were lower in reared groups than C‐WID (29.99%); and EPA + DHA were similar in all groups (15.1–16.61% vs. 27.99%). Despite the good growth and survival, the final mean weight was below that requested by the market (400–500 g). Future research efforts should focus on reducing the feed conversion rate (3:1).     

Age estimation of the wild population of Japanese mantis shrimp <Emphasis Type="Italic">Oratosquilla oratoria</Emphasis> (Crustacea: Stomatopoda) in Tokyo Bay,Japan, using lipofuscin as an age marker

ABSTRACT:   In this study, the age composition of the Japanese mantis shrimp, Oratosquilla oratoria , in Tokyo Bay, central Japan, was investigated using lipofuscin, an autofluorescent pigment, as an age marker. Lipofuscin in a histological section of protocerebral bridge cell mass (PBCM) in the brain was identified by confocal microscopy, and its concentration was quantified by image analysis. Modal analysis of the lipofuscin concentration showed four regularly-spaced modes that could each be regarded as a distinct age group. This implied a constant lipofuscin accumulation in PBCM at a 6.5 × 10⁻²% volume fraction per year; it also implied the existence of individuals that are at least 4 years old. The lipofuscin concentration was found to be a more appropriate index than body length for estimating the age of O. oratoria , because the modal analysis on the body–length histogram failed to detect apparent age groups. This was probably a result of the declining growth rate with age and the individual variations in growth through molting leading to considerable overlap in the size between different age groups. The lipofuscin analysis suggested that fast-growing individuals in each cohort are recruited to the fishery, and most individuals attain the exploitable size between 2 and 3 years of age.     

Effects of stocking density,ration and temperature on growth,survival and metamorphosis of auricularia larvae of the California sea cucumber,Parastichopus californicus

The combined effects of stocking density (0.2, 0.5, 1, 2, 4 and 8 inds/ml) and dietary microalgal ration (20,000 and 40,000 cells/ml) and the sole effect of temperature (10, 12, 14, 16, 18 and 22°C) on the specific growth rate (SGR), per cent survival and per cent metamorphosis of auricularia larvae of the California sea cucumber, Parastichopus californicus, were evaluated in two separate experiments. The SGR was not significantly affected by stocking densities in the range of 0.2 to 4 inds/ml, but was significantly reduced at 8 inds/ml. The SGR of larvae fed 20,000 cells/ml was significantly reduced in comparison to those fed 40,000 cells/ml. Larvae had significantly higher per cent survival and per cent metamorphosis when reared at densities of 0.2 and 0.5 inds/ml compared with those reared at 2–8 inds/ml. Microalgal ration level did not significantly impact survival or metamorphosis. Larvae reared at 16 and 18°C had significantly higher SGRs and per cent metamorphosis than those held at all other temperatures, while per cent survival was highest at 16°C. Based on these results, we recommend rearing auricularia larvae of P. californicus at a stocking density at or below 0.5 inds/ml, a dietary ration of 40,000 cells/ml, and a temperature of 16°C.     

拖网渔船船-机-桨-网匹配研究

在拖网渔船的设计中,需要重点考虑螺旋桨与船-机的匹配、渔具与船-机-桨的匹配,实现推进系统的高效能发挥。本文引入时间概率的最佳螺旋桨参数优化确定方法,考虑拖网渔船设计的限制条件,通过优化分析,达到运营工况综合效能最佳,实现螺旋桨与船-机的合理匹配。从拖网渔船数据库中选取30艘运营状况优良的渔船进行有效拖力计算,建立拖网渔船有效拖力与主机功率和拖速的多元非线性回归方程,依据此方程得出的有效拖力结果选择网具和网板,实现有效拖力与渔具的合理匹配,最终实现渔具与船-机-桨的合理匹配。通过实船计算对比,验证了回归的有效拖力估算公式误差范围和适用性。研究表明:在拖网渔船设计初期,可以利用该公式估算有效拖力进行网具和网板的匹配,实现技术经济优化论证,最终实现船-机-桨-网的优化匹配。     

圆口铜鱼精浆的理化性质分析

对圆口铜鱼(Coreius guichenoti)精浆离子和氨基酸成分及精液生理特性进行了检测分析。结果显示,圆口铜鱼精液pH值为7.3,呈弱碱性;精液浓度为39.7%,精子密度为5.3×10~9个/mL;精浆离子以Na~+含量88.7 mmol/L最高,其次是K~+,之后为Ca~(2+)、Mg~(2+)、Zn~(2+)、Cu~(2+);精浆水解氨基酸总量为2 872.69μmol/100mL,其中以脯氨酸含量最高,蛋氨酸、酪氨酸和组氨酸含量最低。该结果填补了圆口铜鱼繁殖生物学的相关数据,为圆口铜鱼规模化人工繁育提供了基础资料。     

Use of the Lincoln Index Mark-Recapture Method to Estimate the Population Densities for Harvestable Yabbies,Cherax destructor,in Grow-Out Ponds

Abstract

The Lin coln In dex mark-re cap ture method was eval u ated for its ac cu racy in es ti mat ing the num ber of harvestable yab bies, Cherax de struc tor, in earthen ponds. Where a sin gle re cap ture event was used to es ti mate the pop u la tion, a 3 to 6 day in ter val be tween the re lease and recap ture of marked an i mals tended to pro vide a more re li able es ti mate than a re lease and re cap ture in ter val of 24 hours. Where two re cap ture events were used to pro vide an av er age es ti mate, the method tended to un der es ti mate by 20% low den sity pop u la tions, that had been the sub ject of pre da tion by wa ter birds, whereas those es ti mates de ter mined f o r ponds with higher den si ties of cray fish, where avian piscivores were excluded, tended to be more ac cu rate (±10%). The ap pli ca tion of pop u la tion es ti ma tion as a tool for ar ti fi cial feed-man age ment is dis cussed.     

Effects of Stocking Density on Composition and Performance of Reared Arctic Charr (Salvelinus alpinus)

Abstract

Proximate composition and performance of Arctic charr (Salvelinus alpinus) stocked at 40, 50, and 75 kg/m³, were determined. Moisture content of fish fillets decreased while their protein and lipid contents increased during the 24 weeks of rearing period. Statistical analyses indicated that moisture, protein and lipid contents of charr flesh varied significantly among density groups while ash contents did not. While the moisture and ash contents of fish fillets were directly related to stocking density (r = +0.9435 and r = +0.9918, respectively), contents of protein and lipid did not (r = ?0.5251 and r = ?0.7038, respectively). The level of carotenoids in the flesh and skin of Arctic charr increased with duration of feeding on pigmented diets. However, no correlation (r = ?0.6053) existed between stocking density and concentration of carotenoids. The specific growth rate (SGR), feed conversion ratio (FCR), and protein efficiency ratio (PER) were significantly influenced by stocking densities but the hepatosomatic index (HSI) of fish did not. These performance parameters of fish were well correlated with stocking density (r = ?0.9368, ?0.9975, ?0.9899, and ?0.9920, respectively). Although SGR, FCR and PER of fish from different stocking densities varied significantly (p < 0.05), their final weights did not.     

Changes in density of under-yearling masu salmon <Emphasis Type="Italic">Oncorhynchus masou</Emphasis> in a natural stream after release

ABSTRACT:   The relation between the density of fish and parameters such as body weight, condition factor and the hepatic triglyceride (TG) content of masu salmon Oncorhynchus masou juveniles after release into a natural stream were studied. Hatchery-reared juveniles of different sizes and numbers were released in May 1999, 2000 and 2001, and investigations were carried out from July to September each year. The density of fish was relatively high in 1999, when juveniles of the largest size and number were released, but then continued to decrease during the investigation. The hepatic TG content remained considerably low in 1999, and there was a significant negative correlation between the density of fish and the hepatic TG content of the juveniles caught over three years. The initial fish size and number at release as well as the nutritional condition of the juveniles may affect the density of fish after release.     

封闭循环水系统中养殖密度对大菱鲆生长和免疫的影响

研究了大菱鲆幼鱼在封闭循环水系统中养殖密度对其摄食、生长、饲料利用率及免疫机能的影响。实验设计了4组不同处理,初始养殖密度分别为0.66 kg/m2、1.26 kg/m2、2.56 kg/m2、4.00 kg/m2,每个密度组设3个重复,为期100 d,实验结束时养殖密度分别为4.67 kg/m2、7.25 kg/m2、14.16 kg/m2、17.77 kg/m2。结果表明:大菱鲆生长速度与养殖密度呈负相关,各实验组的持定生长率(SGR)值分别为2.67、2.33、2.29、1.98;随着养殖密度的增加,各实验组大菱鲆的体重差异度出现显著变化(P<0.01);大菱鲆的饵料系数与养殖密度呈正相关,实验组1的饵料系数为0.70;实验组4的饵料系数为0.76;养殖密度对大菱鲆的免疫指标碱性磷酸酶(AKP)、酸性磷酸酶(ACP)及肝脏的脏器系数的影响不大。本实验结果可为鱼类循环水工厂化养殖管理提供参考。