帆张网网囊网目尺寸对小黄鱼的选择性

为探索帆张网不同网目尺寸网囊对小黄鱼的选择性,2017年4月在舟山渔场中部用传统方法(套网法)对5种不同网目尺寸(35 mm、45 mm、55 mm、60 mm、65 mm)网囊开展了选择性实验。应用Logistic模型对小黄鱼选择性曲线进行拟合,采用极大似然法估算模型参数。结果显示:①实验期间主要捕获对象为小黄鱼,数量和重量分别占比66.94%和84.48%,体长范围71～190 mm,平均体长124 mm;②随着网目尺寸的增加,网囊中小黄鱼优势体长总体上大于套网;③网囊网目尺寸为35 mm、45 mm、55 mm、60 mm和65 mm时,小黄鱼L50分别为80.425 mm、103.496 mm、119.711 mm、122.676 mm和137.026 mm,SR分别为50.202 mm、52.540 mm、61.120 mm、41.730 mm和63.560 mm,L50呈现逐渐增大的趋势;④小黄鱼网囊网目尺寸(m)与50%选择体长(L50)的关系为L50=1.776 m+20.300 (R2=0.980);⑤5种网目尺寸网囊中小黄鱼尾数逃逸率均高于重量逃逸率,网囊网目尺寸≤45 mm时,其尾数及重量逃逸率均低于5%,网囊网目尺寸≥55 mm时,其尾数及重量逃逸率均超过10%,甚至可达50%。综合分析,目前实施的55 mm网目尺寸能有效释放小黄鱼幼鱼,但网目尺寸仍需扩大。     

东海区方形目与菱形目拖网网囊对小黄鱼的选择性研究

采用套网法对双船底拖网不同网目尺寸(40、50、60、65 mm)的方形目和菱形目网囊捕捞东海区小黄鱼(Larimichthys polyactis)进行选择性实验,对不同网囊网目结构、不同网囊网目尺寸的选择性数据进行了比较分析。结果表明:(1)网囊网目尺寸小于50 mm,小黄鱼的逃逸率极低,网目结构选择性差异不明显。大于50 mm时,方形目网囊逃逸率均略高于菱形目结构,但方形目与菱形目逃逸率差异并不显著(P0.05)。(2)网目尺寸为50 mm、60 mm和65 mm时,方形目网囊的50%选择体长(L_(0.5))分别比菱形目网囊的L_(0.5)大28.5%、16.8%和7.3%,方形目网囊对于小黄鱼具有较好的选择性。(3)根据小黄鱼的50%选择体长(L_(0.5)),结合现行可捕体长标准以及不同阶段渔获物体型特征,建议菱形网目尺寸为60 mm或者方形网目尺寸为55 mm,二者具有相同的选择性和渔获率。     

桁拖网不同网目结构的网囊对虾类的选择性

为改善东海近海桁拖网对主要虾类的选择性,使用对比作业法,在吕泗渔场开展了多个航次、不同网目结构（菱形、方形及转向网目）网囊的选择性试验,并进行了选择性分析。在选择性分析中,将几何相似原理运用于选择性曲线模型（Richards曲线）,并使用极大似然估计法进行参数估计,同时使用假设检验理论对选择性曲线模型进行简化。选择性模型对哈氏仿对虾（Parapenaeopsis hardwickii）和葛氏长臂虾（Palaemon gravier）渔获数据的拟合结果显示,选择性模型具有较好的拟合性,但存在航次间差异;不同网目结构网囊的选择性曲线模型都可简化为Logistic曲线;对于哈氏仿对虾,相比菱形网目网囊,方形网目和转向网目网囊的L50较大,而SR较小（菱形和方形网目之间差异显著,菱形和转向网目之间差异不显著）;对于葛氏长臂虾,方形网目和转向网目网囊的L50较大（菱形和方形网目之间差异显著,菱形和转向网目之间差异不显著）。根据虾类在网囊中的逃逸行为,方形网目、转向网目具有较好选择性的原因在于这2种网目较传统菱形网目不易合拢;不同网目结构网囊的选择性对开展渔具种类选择性研究具有重要意义。     

Evaluation of codends with sorting grids, exit windows, and diamond meshes: Size selection and fish behaviour

This paper presents the results of an experiment aimed at improving the size selection of cod (Gadus morhua) and haddock (Melanogrammus aeglefinus) in the Nordic bottom trawl fishery. Three systems simulating commercial conditions were tested: a 135 mm diamond-mesh codend fitted with a 55 mm sorting grid (Sort-V); a 135 mm diamond-mesh codend fitted with two lateral exit windows; and a codend built entirely of 155 mm diamond mesh. The selectivity curves showed similar selection ranges (SR) for the three systems. For cod, the mean SRs were around 8 cm, while for haddock, they were around 6 cm. All the estimated l₅₀ values were far above the minimum landing sizes (MLS). For cod, the mean l₅₀s were 56.1, 53.9, and 60.7 cm for the sorting grid, exit windows, and diamond-mesh configurations, respectively, while for haddock, they were 50.2, 50.6, and 49.9 cm, respectively. Underwater observations revealed that most of the fish escaped from the grid and exit-window codends as soon as they reached the vicinity of the sorting device. In contrast, fish remained inside the diamond-mesh codend for a longer time, and consequently were more exposed to physical damage before escape. In addition, many fish escaped from this codend during haul back and these fish were not likely to survive due to the rapid changes in pressure. Thus, the selectivity results obtained with this type of codend should be interpreted carefully.     

Digestibility of nutrients and energy in ingredients for bullfrogs during different phases of development

The ability of frogs to digest dietary nutrients changes with growth, with the animals becoming more or less demanding. The objective of this study was to determine the apparent digestibility coefficients of protein, energy and ether extract of 14 ingredients used in bullfrog diets (spray‐dried blood meal, hydrolysed feather meal, poultry by‐product meal, red blood cell concentrate, tilapia by‐product meal, sardine fishmeal, salmon fishmeal, meat and bone meal, corn gluten meal, soybean meal, corn, wheat bran, soy protein concentrate and soybean oil). A total of 2,325 bullfrogs (Lithobates catesbeianus) in different phases of development were used: early phase (mean weight of 30–50 g), growth phase (80–110 g) and finishing phase (150–200 g). Faeces were collected using the method of dissection. Marked differences in digestibility of the ingredients were observed between the different phases of frog development. Among the ingredients studied, salmon fishmeal and corn gluten meal showed good utilization of the protein (78.9% and 86.7%, respectively) and energy fraction (89.4% and 83.3%, respectively). The salmon fishmeal, poultry by‐product meal, sardine fishmeal, soy protein concentrate, wheat bran and soybean oil exhibited good ether extract utilization (81.2%–92.8%), recommending their use in bullfrog diets.     

不同尺寸网目与缩结系数对许氏平鲉的选择性

为探究不同尺寸网目及缩结系数对许氏平鲉(Sebastesschlegelii)的选择性,本研究基于实验水槽中的套网法试验,测得许氏平鲉的生物学特征参数,采用Logistic模型曲线拟合得到不同尺寸网目及缩结系数对许氏平鲉的选择性曲线,并用极大似然法估算选择性参数。结果表明:网目尺寸为63 mm、82 mm、93 mm时,许氏平鲉的50%选择性体长(L50)分别为18.49 cm、23.90 cm、25.12 cm,选择范围(SR)分别为3.18、3.6、3.85,选择因素(SF)分别为2.93、2.91、2.70,随着网目尺寸的增大,许氏平鲉的L50、SR逐渐增大, SF逐渐减小;当82 mm网目的缩结系数(Et)分别为0.5、0.6、0.707时,许氏平鲉的50%选择性体长(L50)分别为21.47 cm、23.90 cm、22.02 cm,选择范围(SR)分别为3.23、3.6、3.38,选择因素(SF)分别为2.65、2.91、2.68,随着网目缩结系数的增大,许氏平鲉的L50、SR、SF先增大后减小,在Et为0.6时均达到最大。为保护许氏平鲉幼鱼资源,建议在鱼礁区使用网目规格为70 mm, Et为0.6的笼壶渔具进行采捕。     

Trawling experiment in a circular water tank to assess the effects of towing speed,light intensity,and mesh shape on active escape of undersized fish

ABSTRACT:   To assess the effect of towing speed and light intensity on the active escape of undersized fish through diamond and square mesh panels, a trawling experiment was simulated in a circular water tank. Juveniles of Japanese dace Tribolodon hakonensis (13-cm length class) were used as experimental fish. They were forced to swim inside a closed framed net with either diamond or square mesh (65-mm mesh size) that was moved using a speed-controllable motor. A submersible infrared CCD camera was used to observe and record the behavior of fish inside the net when it passed in front of the camera. Results indicated significant effects of towing speeds and light intensities ( P  < 0.05) on the escape of fish through the diamond and square meshes. Increase in light intensity enhanced the ability of fish to escape at lower towing speeds. At higher towing speeds, few fish could escape under light conditions. A strong negative correlation was found between towing speed and the frequency of fish escape (diamond mesh R ² = 0.99, square mesh R ² = 0.96). There was no significant difference between the numbers of fish escaping through the diamond and square meshes. These results suggest that the square-mesh panel may not be effective in the trawl cod end under dark or very low light intensity at high towing speed.     

人工鱼礁区不同网目尺寸单片刺网对许氏平鲉和大泷六线鱼的选择性

为探究人工鱼礁区单片刺网对许氏平鲉(Sebastes schlegeli)和大泷六线鱼(Hexagrammos otakii)的选择性, 于 2021 年 10 月在荣成北部人工鱼礁区使用 4 种网目尺寸(40 mm、50 mm、60 mm、70 mm)的单片刺网进行选择性实验。在 SELECT 模型的架构下, 使用 Normal、Lognormal、Gamma、Bi-normal 模型进行选择性拟合, 根据赤池信息指数(AIC)和模型残差(MD)选择最佳拟合模型。结果表明: Lognormal 模型拟合效果最佳, 其 AIC 值和 MD 值均为最低值。根据 Lognormal 模型, 不同网目尺寸许氏平鲉的模型拟合长度分别为 114.23 mm、142.79 mm、 171.35 mm、199.90 mm; 大泷六线鱼的模型拟合长度分别为 129.67 mm、162.09 mm、194.51 mm、226.92 mm。许氏平鲉和大泷六线鱼的体长与最大剖面周长的线性关系分别为: G=0.2877L+0.7463(R² =0.6722), G=0.2468L– 3.8531(R² =0.6851)。选取 150 mm 作为许氏平鲉和大泷六线鱼的理论成熟体长(MBL)进行分析, 结合幼鱼留存比例, 发现网目尺寸为 60 mm 和 70 mm 的刺网能够保护人工鱼礁区许氏平鲉和大泷六线鱼的幼鱼资源。研究结果可为人工鱼礁区渔业资源的管理和养护提供参考。     

三种不同养殖品种池塘水质变化特征分析及比较

研究了养殖泥鳅、翘嘴红鲌和青虾池塘的水质变化特点,并用VIKOR算法比较了三种养殖品种的池塘水环境质量。结果表明:三种养殖品种池塘的水质变化特点基本相同,但是三种池塘中,青虾养殖池塘水质最优,泥鳅池塘次之,翘嘴红鲌池塘最差。     

Comparison of visual acuity and visual axis of three flatfish species with different ecotypes

ABSTRACT:   The visual acuity, visual axis and visual accommodation of pointhead flounder, slime flounder, and red halibut were determined to obtain basic knowledge for developing appropriate fishing gear and fishing methods for sustainable fisheries. Each of these species has a different ecotype in terms of habitat, depth and prey species. Thus, it was hypothesized that they may differ in terms of visual acuity, visual axis and visual accommodation. Few studies have compared these characters in flatfishes from different ecotypes. We used histological methods to determine visual acuity (i.e. cone cell density) and visual axis (i.e. cone cell distribution) in each of these species. The maximum visual acuity was 0.127 in pointhead flounder (total length, TL 344 mm), 0.092 in slime flounder (TL 372 mm) and 0.109 in red halibut (TL 336 mm). Based on the cone cell distribution in the retina, the visual axis was upward and forward in pointhead flounder, forward and downward in slime flounder, and downward in red halibut. Finally, the mean angle of lens movement was −2° in pointhead flounder, −13° in slime flounder and −32° in red halibut. This measurement of lens movement indicated that the average near-point distance was 0.87 × TL in pointhead flounder, 0.65 × TL in slime flounder and 1.02 × TL in red halibut. At similar TL (336–355 mm), the visual acuity of these species differs depending on the direction in which they are looking.     

Evaluation of a simple means to reduce discard in the Kattegat-Skagerrak Nephrops (Nephrops norvegicus) fishery: Commercial testing of different codends and square-mesh panels

Discarding of fish species in the Kattegat-Skagerrak Nephrops directed fisheries remains at high levels. In this work we have tested four sets of codends pair-wise with the catch comparison technique under full commercial conditions to assess their potential in reducing the catch of undersized commercial species, in particular cod. We investigate the position of a 90 mm square-mesh panel (SMP), the effect of increasing the mesh size from 90 to 120 mm in the SMP, the effect of inserting a 90 mm SMP in an 80 mm codend and the effect of increasing the codend mesh size from 90 to 120 mm in a total of 89 hauls. Inserting the SMP 3–6 m from the codline compared to 6–9 m from the codline, reduced catches of cod above the minimum landing size (MLS) and Nephrops above and below the MLS. Increasing the mesh size in the SMP from 90 to 120 mm increased the catch of cod above the MLS in weight with an overall increase of 12% in the revenue. The effect of installing a 90 mm SMP 6–9 m from the codline in a nominal 80 mm codend had no effect on the catch of cod. Increasing the nominal codend mesh size from 90 to 120 mm reduced the catch of all species below the MLS, except monkfish. Catches of Nephrops above the MLS were, however, reduced by approximately one third and the total loss in revenue was 21%.     

Response of juvenile astacid crayfish (Pacifastacus leniusculus) to three commercial dry diets with different protein levels during the first 6 months of intensive rearing

A 180‐day experiment was carried out under controlled conditions to compare the effects of three commercial dry diets on survival, growth and body composition of juvenile Pacifastacus leniusculus from the onset of exogenous feeding (stage 2). Protein levels in the diets were 55.5% [high‐protein content (HP) diet], 40.3% [medium‐protein content (MP)] and 33.2% [low‐protein content (LP)]. Diets were supplemented with restricted amounts of live fresh Artemia nauplii up to day 120. No significant differences in survival among diets were found along the trial, with final values around 68.5%. During the live feed supplementation, growth was similar with the three diets. At the end of the trial, weight with HP or with MP was similar (around 2.32 g) and significantly higher than with LP (1.97 g). Thus, a diet with 40% of protein can be suitable, as it allowed similar results as the diet containing 55%. Levels of protein in diets and in crayfish muscle were positively correlated (r=0.8). This study also shows that an intensive rearing up to 180 days with good survival and growth rates is possible using dry diets for finfish species supplemented with live feed.     

高位虾池养殖后期浮游微藻群落结构特征

2008年7月1～15日,在广东省红海湾对虾养殖区域选取3口养殖84～98 d的高位池,对养殖水体浮游微藻和常规水质因子进行每天1次采样分析.共检出浮游微藻6门25种,其中绿藻10种,硅藻两种,甲藻7种,裸藻4种,蓝藻1种,金藻1种.浮游微藻细胞数量介于5.13×108～4.01×109ind/L,生物量为42.92～181.73 mg/L,数量多样性指数平均为1.01～1.30,生物量多样性指数平均为1.83～2.27.优势种主要是蛋白核小球藻和绿色颤藻,二者的优势度之和高达90%,控制着浮游微藻总数量的变动趋势.从各门藻类生物量对总生物量贡献多少来看,对虾高位池养殖后期是以蓝藻门、绿藻门和硅藻门为优势类群而组成的浮游微藻群落结构.     

河川沙塘鳢不同家系生长性能的比较及优良亲本选择

采用巢式设计,对河川沙塘鳢(Odontobutis potamophila)四个不同地理群体(建德、当涂、射阳和苏州)进行群体内和群体间杂交,构建了34个全同胞家系,进而分析了不同家系子代的生长性状指标,方差分析和多重比较结果显示:不同家系的子代在生长性能上差异显著。其中,在整个生长测量过程中,F36、F35、F29、F16和F1号等家系无论是全长还是体重都表现较优的生长速度和增长量,生长优势明显,由此可判断F36、F35、F29、F16和F1等家系为优秀家系,可作为该品种进一步选育的基础群体。对34个河川沙塘鳢家系亲本来源与子代生长性能的相关性分析结果表明,生长性能良好的河川沙塘鳢家系中,父本来源于建德群体的居多,母本来源于当涂群体的居多。可见建德群体适合作父本,当涂群体适合作母本。     

三种不同游泳习性鱼类骨骼肌的快、慢肌纤维组织学特性

硬骨鱼类的骨骼肌可为其游泳运动提供动力。为认识不同游泳习性鱼类的骨骼肌肌纤维组织学特征,本研究选取3种具有不同游泳习性的鱼类：鲐(Scomber japonicus)、大黄鱼(Larimichthys crocea)和褐牙鲆(Paralichthys olivaceus),采用石蜡切片苏木精–伊红染色法和形态计量法,以形状、直径和密度作为评价指标,对其骨骼肌的快、慢肌纤维组织学特性进行表征,比较3种不同游泳习性鱼类的快、慢肌纤维组织学特征差异。组织学观察发现,3种类型鱼类的骨骼肌快、慢肌纤维横切面均呈不规则形状。营持续式游泳的鲐的快肌纤维呈多角状,慢肌纤维呈多边柱形;营延长式游泳的大黄鱼的快、慢肌纤维呈长椭圆形;营爆发式游泳的褐牙鲆的快、慢肌纤维呈扁椭圆形。形态计量结果显示,3种鱼类的快肌纤维直径均极显著大于其慢肌纤维(P<0.01)。大黄鱼的慢肌纤维直径在3种鱼类中最大,约为鲐的1.34倍、褐牙鲆的1.14倍;鲐的快肌纤维直径在3种鱼类中最大,约为大黄鱼的1.41倍、褐牙鲆的1.35倍。3种鱼类的快肌纤维密度均极显著小于其慢肌纤维(P<0.01),其中,快肌纤维密度大小排...     

三种不同养殖模式下大黄鱼鱼皮、鱼鳞挥发性风味成分分析

为了探讨不同养殖模式对大黄鱼(Pseudosciaena crocea)挥发性风味成分的影响,对于养殖大黄鱼的风味评价和养殖模式优化具有重要的现实意义。采用顶空固相微萃取-全二维气相色谱/飞行时间质谱技术对小网箱、深水网箱和围网养殖大黄鱼的鱼皮、鱼鳞挥发性风味成分进行了分析。结果表明:小网箱(X)、深水网箱(S)和围网(W)养殖大黄鱼的鱼皮(P)、鱼鳞(L)中共检测出醛类、醇类、酮类、脂类、烃类及其他共118种挥发性成分,其中醛类、醇类、酮类和烃类含量较高。3种模式养殖大黄鱼的鱼皮、鱼鳞中挥发性成分存在显著性差异(P0.05),且羰基化合物和醇类含量变化较大。在3种模式养殖大黄鱼的鱼皮中,围网养殖的鱼皮(WP)羰基化合物和醇类含量最高,SP次之,XP最低(P0.05)。在3种模式养殖大黄鱼的鱼鳞中,WL的羰基化合物和醇类含量显著高于XL和SL(P0.05),而XL与SL的羰基化合物和醇类含量无显著差异(P0.05)。通过相对气味活度值法,在3种模式养殖大黄鱼的鱼皮中分别筛选出5、15、13种主体风味成分,与XP相比,WP和SP主体风味成分数量和种类更多。在3种模式养殖大黄鱼的鱼鳞中分别筛选出9、10、16种主体风味成分,与XL和SL相比,WL中主体风味成分数量和种类更多。结论显示,W组羰基化合物和醇类含量最高,风味物质构成最优;主体风味成分的数量和种类最多,风味最丰富。     

Effect of temperature and photoperiod on the reproductive condition and performance of a tropical damselfish <Emphasis Type="Italic">Chrysiptera cyanea</Emphasis> during different phases of the reproductive season

Effects of temperature and photoperiod on the reproductive activity of a reef associated tropical damselfish Chrysiptera cyanea were evaluated under three phases with different environmental patterns, phase I (April–May; increasing water temperature and photoperiod), phase II (June–July; increasing water temperature and peak/decreasing photoperiod), and phase III (August–September; peak/decreasing water temperature and decreasing photoperiod). When the fish were reared at 20, 25, or 30°C under natural photoperiod, the reproductive conditions differed within and among the phases depending on experimental temperature and environmental patterns. From phases I through III, ovaries with vitellogenic oocytes were notable only at 25°C, whereas regressing and immature oocytes were noticed at 20 and 30°C. The fish underwent active spawning at 25°C, whereas no or few spawnings were observed at other temperatures. In phase III, there was a resultant prevention of decrease in the gonadosomatic index and disappearance of vitellogenic oocytes in the ovaries of fish under a long photoperiod (LD14:10) compared to those under a short photoperiod (LD10:14). These results indicate that a long photoperiod with a suitable range of water temperature is a principal determinant in continuity of reproductive activity and performance, and that a high temperature has a negative impact on their ovarian development.     

Selectivity of the rotifer Brachionus plicatilis fed mixtures of algal species with various cell volumes and cell densities

The ability for food selectivity of rotifer Brachionus plicatiliswas studied in the laboratory by feeding mixtures of microalgae with various cell volumes. Chlorella sp. (≈22 µm³) was the reference algal species, and Asteromonas gracilis, (Chlorophyta) (≈2150 µm³), Tetraselmis suesica (≈268 µm³), Dunaliella salina (≈52 µm³) and Chaetoceros sp. (≈150 µm³) the experimental species. Each was mixed with Chlorella and fed in three experiments. In the first experiment, filtration and ingestion rates of rotifers each fed with algae revealed that the highest values were measured with the mixture of Chlorella + Asteromonas, and the lowest for Chlorella + Chaetoceros. In the second and the third experiments, by using several combinations of algal densities with the mixture of Chlorella + Asteromonas, a selectivity ability of the rotifers for Asteromonas was found. A hypothesis is presented that accounts for the preference of rotifers for Asteromonas, which is suggested as a new candidate species for use in live food production of fish hatcheries.