基于不同人工鱼巢研究黄颡鱼的产卵偏好性

为探索黄颡鱼(Pelteobagrus fulvidraco)繁殖时期对人工鱼巢的偏好性, 2018年6—7月开展了不同水温条件下黄颡鱼对不同鱼巢颜色和材质产卵偏好性的对比实验。实验用产卵鱼巢为半球形棕榈空鱼巢(直径25 cm,深12 cm);同规格内部放置4～6枚碎石块的棕榈鱼巢和塑料鱼巢;折叠6层尼龙渔网(30cm×40cm)和棕榈片(30cm×40cm)鱼巢,于水泥池(290 cm×120 cm×100 cm)内开展两种温度区间条件下产卵偏好性实验。实验用黄颡鱼亲本雌雄比例为1:1,雌鱼体长(167.8±19.0)mm,体重(99.9±21.7)g;雄鱼体长(235.1±18.8)mm,体重(188.5±38.1)g。结果表明,在24～26℃水环境下,半球形棕色棕榈(无石子)鱼巢内个体平均附卵量为628.49粒/m2,个体单位面积平均附卵率为2.77%;28～32℃水环境下,半球形棕榈(无石子)个体平均附卵量为225.48粒/m2,个体单位面积平均附卵率为1.40%。结果分析发现, 24～26℃是黄颡鱼产卵的最适水温区间;黄颡鱼对棕色鱼巢产卵偏好显著(P0.05),而对灰色、粉色、黄色和绿色无明显偏好;黄颡鱼对半球形棕榈(无石子)鱼巢产卵偏好显著(P0.05),而对其他材质鱼巢的偏好性依次为:半球形棕榈(有石子)平铺棕榈片悬挂棕榈片半球形塑料水泥池。可见,黄颡鱼产卵的最佳偏好为24～26℃水环境下棕色半球形棕榈鱼巢。本研究结果对黄颡鱼的人工繁殖、产沉黏性卵鱼类产卵场的修复和资源增殖有重要的指导意义。     

瓦氏雅罗鱼耐碱性状相关分子标记的筛选

本研究以来自达里湖(碱水)和松花江(淡水)的瓦氏雅罗鱼(Leuciscus waleckii)杂交F2为实验材料,通过碱度耐受实验进行性状测定,以39对多态的EST-SSR和SSR为标记,对77个F2个体进行基因分型,根据Fisher确切概率法对F2基因型和耐碱性状进行关联分析。结果发现,有2个标记与耐碱性状显著相关(P0.05),其中1个标记为EST-SSR,从瓦氏雅罗鱼转录组数据库中调取该EST序列,基因注释结果显示该序列与团头鲂(Megalobrama amblycephala)低氧诱导因子HIF-3?基因、草鱼的低氧诱导因子HIF-4?基因具有很高的同源性。该基因的主要功能是参与鱼类的耐低氧反应过程,加强鱼类的耐低氧能力。本研究对于今后深入研究此功能基因的作用机制及培育适于盐碱水域养殖的鱼类新品种具有重要的意义。     

流水和静水条件下鲢幼鱼对不同强度光源的趋性行为研究

结合鱼类的集群行为,探究了在流水和静水处理下鲢(Hypophthalmichthys molitrix)幼鱼的光强偏好。实验流速工况设置包括静水和流水(流速为0.1m/s),光强水平设置为0、10、20、40、70、110lx,并依次进行了实验对象的个体(1尾)实验和群体(5尾)实验。结果显示:(1)个体流水处理在不同光照度水平下的吸引率和排斥率均无显著性差异(P0.05),但个体静水处理20lx和110lx组的光吸引率显著大于40lx和70lx组(P0.05),其他均无显著差异(P0.05);(2)不同流速和实验鱼数量下的光吸引率,由高到低依次为群体流水处理、群体静水处理、个体流水处理、个体静水处理。光排斥率由高到低依次为个体静水处理、个体流水处理、群体静水处理、群体流水处理。研究表明,一定水流速度能够刺激鲢幼鱼趋流,从而提高光的吸引作用,且群体的趋光性要强于个体;(3)流水处理下,鲢幼鱼的最近邻距离(DNN,群体紧凑程度指标)随光强的增大,先减小后增大,集群程度先升高后降低,其中,70lx水平对应的DNN显著高于0lx(F=1.489,P0.05),而静水处理下各光强水平对应的实验鱼DNN无显著性差异(P0.05),集群行为无明显变化。     

高体鳑鲏幼鱼集群行为研究

为了探究高体鳑鲏(Rhodeus ocellatus)幼鱼的集群行为,选取248尾幼鱼,分别了组成单独1尾个体和2、4、8和16尾高体鳑鲏幼鱼的群体(N=8),在(25±1)℃水温条件下进行15 min的视频拍摄,随后进行运动轨迹的提取和分析,得到游泳速度以及空间分布特征的相关数据。结果显示:(1)高体鳑鲏的自发游泳速度在0~10 cm/s,1、2、4、8和16个体组的速度中位数分别为4.3 cm/s、4.1 cm/s、3.6 cm/s、3.2 cm/s和4.6 cm/s,其中8个体组的速度中位数显著低于1和16个体组(P0.05)。各组游泳速度的同步性较高,且随群体大小的上升呈显著下降的趋势(P0.05);(2)焦点鱼和群体中其它个体的最近邻距离(NND)出现在0~10 cm,2和4个体组的NND分别为3.1 cm和2.7 cm,显著大于8和16个体组的1.9 cm和2.4 cm(P0.05);(3)2和4个体组排列的极性为91.5%和91.2%,显著高于8和16个体组的82.6%和77.2%(P0.05)。研究结果表明,高体鳑鲏幼鱼具有显著的集群性特征,可能为其适应复杂的生境、提高觅食效率和降低捕食压力的结果;群体大小对高体鳑鲏集群行为特征有显著影响,随群体大小的上升,其群体凝聚力上升,但协调性下降。     

红水河岩滩水库鱼类资源声学评估

为评估梯级开发下渔业资源变化情况,2015年9月采用分裂波束鱼探仪EY60(120 kHz,250 W)对红水河岩滩水库库区及上游江段鱼类资源进行声学调查,并结合渔获物统计和地理统计分析对鱼类时空分布进行分析,评估鱼类资源量。结果显示整个调查区域的鱼类资源密度为(0.53±2.11)尾·m~(-2)(±SD),从水坝上游至库区呈增长趋势,鱼类资源密度水平分布与水深无显著相关关系。垂直分布方面,鱼类主要分布在30 m以内水层;不同大小个体对水深有一定的选择性,小个体鱼类(10 cm)约86.2%分布在30 m水层之内;大个体(30 cm)有44.7%分布在40 m以下水层。基于鱼类分布GIS建模,估算调查区域鱼类资源量为6.57×10~7尾。     

黄鳍棘鲷标志放流群体的规格适宜性评价

合理选取标志放流鱼的规格是成功监测放流鱼类动态及评估增殖效果的关键步骤。本研究以黄鳍棘鲷为对象,通过2个实验评价标志鱼的适宜规格。实验1对比了4种体长的黄鳍棘鲷(平均体长5、7、11和14 cm)作T型标志后其生长、存活和标志保留情况,并利用逻辑斯蒂回归模型分别分析标志鱼存活率和标志保留率的规格特异性;实验2模拟了不同混合比例下2种体长黄鳍棘鲷标志鱼与不标志鱼的捕捞情况,并利用重抽样方法对捕捞结果作计算机重抽样,分析2种鱼能否充分混合以及标志鱼的规格、比例对捕捞结果的影响。结果显示:(1)7、11和14 cm标志组的特定生长率与对照组无显著差异;(2)标志鱼的存活率随体长的增加而增加(5 cm标志组的鱼在标志后7 d内全部死亡,7、11和14 cm标志组的存活率分别为77.5%、92.5%和100.0%)。标志鱼的存活率与初始体长的逻辑斯蒂回归关系式为P=exp(0.099X-6.900)/[1+exp(0.099X-6.900)];(3)各组的标志保留率较高(7、11和14 cm标志组的标志保留率分别为97.5%、100.0%和100.0%),但与体长无明显关系;(4)模拟捕捞结果与计算机重抽样结果无显著差异,二者均不受鱼体规格的影响,但受标志鱼比例的影响极显著,标志鱼比例越高,其捕获率也越高。综上,建议今后采用T型标志方法开展增殖放流品种(如黄鳍棘鲷)的相关研究时,应综合考虑成本和可接受的误差范围以选择符合研究目的的标志鱼规格,若需标志鱼的存活率高于50.0%,则体长至少为7 cm,高于75.0%则体长至少为8 cm,高于95.0%则体长至少为10 cm。此外,在成本允许的条件下,建议尽可能增加放流鱼类中标志鱼的比例以提高增殖效果评估的代表性,而具体适宜的比例值得深入研究。     

总溶解气体(TDG)过饱和胁迫对中华倒刺鲃(Spinibarbus sinensis)血液生理指标的影响

为解析总溶解气体(TDG)过饱和导致鱼类发病的机理,本研究以长江上游特有土著鱼类中华倒刺鲃(Spinibarbus sinensis)为实验对象,通过将其暴露在4个不同浓度TDG过饱和水中,测定其酸碱度(pH)、二氧化碳分压(pCO_2)、碳酸氢根(HCO~-_3)、总二氧化碳(TCO_2)、葡萄糖(Glu)、红细胞压积(Hct)、血红蛋白(Hb)、钠离子(Na~+)和氯离子(Cl~-)等9个血液生理指标,分析其变动规律及变动原因。结果显示:(1)不同浓度TDG过饱和胁迫各组之间,实验鱼耐受时间、外观特征存在较大差异,各组实验鱼分别暴露15、10、4.25、5 h后,身体失去平衡和自主游泳能力,高浓度组(G3、G4)较低浓度组(G1、G2)实验鱼体表更容易出现典型气泡病特征;(2)TDG过饱和胁迫各组鱼类血液pH较对照组均显著降低,pCO_2、HCO~-_3、TCO_2、Glu、K~+较对照组均显著升高,Hct、Hb、Na~+、Cl~-较对照组差异不显著;(3)TDG过饱和胁迫各组之间鱼类的血液pH、pCO_2、HCO~-_3、TCO_2、Glu、Hct、Hb、Na~+和Cl~-等9个指标均差异不显著。结果提示,TDG过饱和胁迫导致中华倒刺鲃发生应激反应,在适应环境变化过程中,血液酸碱平衡失调,机体发生酸中毒。     

光唇鱼对单色光偏好的性别差异及相关生理机制

为探究溪流性鱼类光唇鱼(Acrossocheilus fasciatus)对光色的偏好是否存在性别差异, 以及芳香化酶作为催化睾酮(T)向雌二醇(estradiol, E2)转化的限速酶在行为调节中的关键角色, 本研究采用行为学方法研究了雌鱼和雄鱼对 6 种单色 LED 光源的选择偏好, 并尝试利用药物抑制体内芳香化酶活力从而改变血浆性激素水平和鱼的行为表现。结果表明, 雌鱼和雄鱼分别相对偏好红光(峰值为 637 nm)和黄光(590 nm), 两者均相对排斥蓝光(465 nm)、 紫光(405 nm)以及含有蓝光波段的白光(447 nm), 而对绿光(518 nm)的偏好不明显。摄食含有芳香化酶抑制剂来曲唑(letrozole, LZ)的实验饲料 10 d 后, 雌性和雄性光唇鱼脑和性腺组织内芳香化酶活力和血浆 E2 水平均显著下降, 但血浆 T 水平无显著变化。值得注意的是, LZ 也导致处理鱼对光色选择偏好的改变, 雌鱼转为相对偏好蓝光, 雄鱼转为相对偏好红光。然而, 摄入含 LZ+E2 实验饲料后除芳香化酶活力降低外, T、E2 两种性激素水平和光色偏好行为表现均未出现明显变化。因此推测光唇鱼对光色偏好的性别差异极可能与体内芳香化酶活力和雌二醇水平的性别差异有关, 而与睾酮水平无明显关联。     

TDG过饱和高含沙水体对鲤幼鱼的影响

高坝泄洪后产生的总溶解气体(Total dissolved gas,TDG)过饱和含沙水体威胁着下游河道鱼类的生存。以鲤(Cyprinus carpio)幼鱼为实验对象,中值粒径为7μm的泥沙为实验用沙,开展不同规格鲤幼鱼受TDG过饱和含沙水体胁迫的耐受性实验。结果表明,实验开始后不久,鲤幼鱼出现较明显的异常行为和气泡病症状;在无沙和含沙量为1 500 mg/L的TDG过饱和(饱和度为125%、130%、135%)水体中,无沙水体第一批实验鱼[体长(6.40±0.10) cm、体重(5.80±0.20) g]的中位生存时间为14.3 h、10.3 h、9.1 h,含沙水体(1 500 mg/L)第一批实验鱼的中位生存时间为13.0 h、9.8 h、7.1 h,两者无显著性差异(P0.05);含沙量为1 500 mg/L的TDG过饱和(饱和度为125%、130%、135%)水体中,第二批小规格实验鱼[体长(5.80±0.25) cm、体重(2.00±0.31) g]的中位生存时间为12.6 h、10.2 h、7.4 h,第三批大规格实验鱼[体长(8.50±0.57) cm、体重(9.50±0.48) g]中位生存时间为11.2 h、8.6 h、4.5 h,两者也无显著差异(P0.05),不同规格实验鱼对TDG过饱和含沙水体的耐受性无明显差异(P0.05)。即使含沙量达到1 500 mg/L,泥沙单独作用并未造成实验鱼异常或死亡,但高饱和度(135%)的过饱和TDG与泥沙共同作用对实验鱼影响较大,降低了实验鱼的中位生存时间(最小值为4.5 h)。     

鲤科鱼类的流速选择及其与食性的关系

为考察食性对鲤科鱼类流速选择行为的影响,本研究选择滤食性的鲢摘要可以不放拉丁学名,请补充在正文出现第一个的位置和鳙、草食性的草鱼和中华倒刺鲃、以及杂食性的鲫和锦鲫作为实验对象;在(25 ± 1) ℃条件下将单尾实验鱼置于梯度流速选择仪（流速范围为11.86-65 .45 cm/s,等距离划分为5个流速区域）中拍摄1 h,采用Ethovision XT19软件分析视频资料并计算六种实验鱼在不同流速区域平均停留时间（Pt,%）、平均进入频次（F,次 / h）和单次进入停留时间（T,s）等流速选择行为指标。结果显示：（1）六种实验鱼的流速选择行为均呈现出两种流速偏好趋势,一类表现为偏好缓流（或静水）（最低流速区域的Pt >50%）,被定义为Ⅰ型;另一类个体Pt随水流速度的变化出现不同程度的波动,最大Pt通常出现在某一中等流速区,则定义为Ⅱ型;（2）食性对鱼类流速偏好行为有显著影响,Ⅰ型个体中滤食性鱼类对静水或缓流偏好显著大于其他两种食性的鱼类,其中鳙和鲢的Ⅰ型个体在最低端流速区域Pt大于92%;滤食性鲢和鳙的Ⅱ型个体偏好流速高于杂食性的鲫和锦鲫。草食性的草鱼和中华倒刺鲃Ⅱ型流速偏好均不明显,但其在中间速流速区域F值最大。研究表明：六种鲤科鱼类的流速偏好行为存在Ⅰ型和Ⅱ型的表型分化并且差异明显,实验鱼的流速偏好行为与食性有关。     

Spatial learning-induced <Emphasis Type="Italic">egr</Emphasis>-<Emphasis Type="Italic">1</Emphasis> expression in telencephalon of gold fish <Emphasis Type="Italic">Carassius auratus</Emphasis>

The immediate-early gene (egr-1) expression was used to examine the neuron’s response in telencephalon of goldfish during spatial learning in small space. Fishes were pre-exposed in the experimental apparatus and trained to pick food from the tray in a rectangular-shaped arena. The apparatus was divided into identical compartments comprising three gates to provide different spatial tasks. After the fish learned to pass through the gate one, two more gates were introduced one by one. Fish made more number of attempts and took longer time (P < 0.05) to pass through the first gate than the gate two or three. This active learning induces the expression of egr-1 in telencephalon as established by western blot analysis. Subsequently, the fish learn quickly to cross the similar type of second and third gate and make fewer errors with a corresponding decline in the level of egr-1 expression. As the fish learned to pass through all the three gates, third gate was replaced by modified gate three. Interestingly, the level of egr-1 expression increased again, when the fish exhibit a high exploratory behavior to cross the modified gate three. The present study shows that egr-1 expression is induced in the telencephalon of goldfish while intensively acquiring geometric spatial information to pass through the gates.     

Composition,Lipid Changes,and Sensory Evaluation of Two Sizes of Channel Catfish During Frozen Storage

The effects of size of fish on composition and of time in storage at -18°C on lipid and sensory changes for channel catfish, Ictalurus punctatus, were investigated. Dressed large (1.0 kg) fish (LF) averaged 13.2% fat, while dressed small (0.3 kg) fish (SF) averaged 10.8% fat (P < 0.05). Moisture was lower (P < 0.05) for LF (68.1 vs. 70.8%). Thiobarbituric acid (TBA) values for LF increased during the first ten months and dropped during the 12th month, while TBA values reached their highest level after the 8th month for SF. Free fatty acids did not change for LF but increased (P < 0.05) throughout storage for SF. Lipids for both sizes of fish were 25% saturated, 58% monounsaturated, and 17% polyunsaturated fatty acids. C 14:0, C 18:0, and C 18:3 acids decreased after 12 months of frozen storage. LF were rated higher (P < 0.05) in flavor for the first four months but were not rated significantly different from SF thereafter. These results indicate that although LF contained more fat, they did not oxidize any more than did SF, and both sizes were acceptable to panelists throughout the study. Thus, if channel catfish is handled and stored properly regardless of size, it should be acceptable even after 12 months frozen storage.     

Habitat utilization and diel behavior of juvenile bull trout (Salvelinus confluentus) at the onset of winter

Abstract— Underwater observations were used to describe habitat use and diel behavior of juvenile bull trout ( Salvelinus confluentus ) at the onset of winter (0.8°C) in a second-order central Idaho stream. All fish observed during daytime counts were concealed beneath "home stones" (mean dimensions 32.3 by 21.9 cm) in primarily pool and run habitats. Focal point depths and velocities averaged 57.2 cm and 4.7 cm/s (home stone removed). Fish maintained stations over substrate with low percentages of fine (< 2 mm, mean= 5.2%) sediment. Concealed bull trout were not evenly distributed across the stream channel. Significantly more home stones were distributed near the midline of the channel, compared to the channel margins. Fish size was positively correlated with home stone size. At night, bull trout exhibited a diel behavioral shift, some fish moved out of daytime concealment cover into the water column. At night, bull trout were observed feeding and resting, primarily in pool and run habitats. During both day and night, bull trout used riffles significantly less frequently than those habitats were available.     

Accuracy of snorkelling counts in assessing spawning stock of Atlantic salmon,Salmo salar,verified by radio‐tagging and underwater video monitoring

Abstract The accuracy of underwater snorkel counts of adult Atlantic salmon, Salmo salar L., was analysed in a small tributary of the River Teno before and during the spawning period using two independent verification methods (video counts and radio‐tagged fish) with known numbers of fish. The observation efficiency of snorkelling crews was generally high, but that of an inexperienced crew (65–72%) was significantly lower than an experienced crew (81–82%). Habitat type affected the accuracy of snorkelers, especially those of the inexperienced crew. The efficiency of snorkelers was high in pool‐type habitats (75–100%) but decreased considerably in faster flowing turbulent habitats (43–82%), where the inexperienced crew provided the lowest estimates. Thus, snorkel counting is a valid method for estimating Atlantic salmon spawning population densities in small rivers with adequate underwater visibility and with a sufficiently experienced snorkelling crew.     

Infrared reflection system for indoor 3D tracking of fish

Many fish rearing infrastructures are already equipped with human-operated camera systems for fish behavior monitoring, e.g. for stopping the feeding system when the fish is satiated or for monitoring of fish behavior abnormalities caused by poor water quality or diseases. The novel infrared reflection (IREF) system for indoor 3D tracking of fish demonstrated in the current study allows for automation of fish behavior monitoring, reducing the system running costs by eliminating the need for continuous human monitoring and increasing the behavioral analysis accuracy by excluding the human subjectivity factor.The operating principle of this system is based on the effect of strong absorption of near infrared (NIR) range light by water, thus allowing estimation of fish distance based on the corresponding fish object brightness on the camera image. The use of NIR illuminator as a part of the IREF system allows fish behavior monitoring in the dark so as not to affect fish circadian rhythm. A system evaluation under aquaculture facility conditions with Atlantic salmon (Salmo salar) using flow-through water in tanks, showed the mean depth estimation error was equal to 5.3 ± 4.0 (SD) cm. The physiological variations among conspecific individual fish introduced the mean depth estimation error of 1.6 ± 1.3 (SD) cm. The advantages of the IREF system over well-known stereo vision systems are lower hardware cost and less computationally intensive 3D coordinates estimation algorithm, while the disadvantage is lower accuracy that is nevertheless acceptable for most applications of aquaculture fish monitoring.     

草鱼洄游适宜流速条件与适应阈值

洄游通道的连通性及其水文条件,是制约鱼类正常洄游和产卵繁殖的关键因素,现有的生态流量相关研究更多侧重于产卵场栖息地模拟,忽略了鱼类洄游水流条件的重要性。为了探究流速条件对鱼类洄游上溯的影响,选取体长(55±5)cm的草鱼(Ctenopharyngodon idellus)为实验对象,通过搭建鱼类洄游仿真河道,营造不同的流速工况,观察不同情景方案下实验鱼群上溯洄游情况,并利用模糊逻辑法对鱼类上溯洄游率、平均上溯时间及上溯持续性等实验参数进行综合分析,探索草鱼洄游的适宜流速条件与适应阈值。结果显示,在流速0.20m/s以下时,草鱼基本无上溯行为;流速0.25～0.80m/s,70%样本在15min内完成上溯,但0.25～0.30m/s时,鱼群上溯缺乏明显的持续性;0.90～1.00m/s时,80%以上样本在5min快速完成上溯;流速超过1.1m/s时,上溯成功率明显降低。研究表明,实验草鱼洄游的适宜流速范围是0.40～1.00m/s,而刺激草鱼洄游的最小流速阈值是0.20m/s。相关结果可为河流生态水力学模拟和河流生态修复以及水利工程生态调度提供技术支撑。     

基于PAE编码系统的短须裂腹鱼行为谱

短须裂腹鱼(Schizothorax wangchiachii)是长江上游特有鱼种。近年来,由于受过度捕捞、水电开发等人类活动影响,短须裂腹鱼自然资源量不断下降。2015年11月—2016年3月,采用焦点动物取样法和随机取样法对短须裂腹鱼的行为谱进行了研究。以"姿势、动作和环境"为轴心,以生态功能为分类依据,构建短须裂腹鱼PAE行为谱。共辨识和定义了自然条件下短须裂腹鱼的10种姿势、22种动作和43种行为。根据行为的生物学功能,将上述行为划分为11大类,即摄食与排遗、探索、领域、发情、交配、护幼、冲突、运动、聚群、休息和杂类行为;区别了各种行为在雄性、雌性和幼体之间的相对发生频次以及发生季节。本研究有助于短须裂腹鱼的行为与保护研究,亦可为其他鱼类的行为谱研究提供参考。     

Behavioral Interactions in Juvenile Channel Catfish,Ictalurus punctatus

Behavioral interactions among juvenile channel catfish, "Ictalurus punctatus," were observed, and fixed action patterns were described and anlyzed. Dominant fish engaged regularly in aggressive activities and never in submissive activities, whereas subordinate fish were observed in submissive activities on a regular basis and rarely in those that were aggressive. Activity levels were significantly higher in dominant fish; however, there was no difference in activity levels between pairs of equal and unequal size fish. A factor analysis indicated that there were three general categoris of behavior in juvenile channel catfish. In addition, two behaviors (which appeared to be displacement activities) were functioning in agnostic encounters. Plasma cortisol concentrations measured in sigle fish and pairs of fish in aquaria and individuals from a holding tank indicated that the least amount of stress occurred in fish that were not interacting with any other individuals. Cortisol levels, however, were lower that those associated with stress levels in fish from other studies.     

The Effects of Water Velocity on the Growth,Dressout, and Body Composition of Channel Catfish,Ictalurus punctatus,Raised in Cicular Tanks

Research was conducted to determine the influence of water velocity on growth, dressout characteristics and fillet proximate composition of channel catfish, Ictalurus punctatus, raised in circular tanks. In this study, channel catfish cultured in water velocities of 4 cm/second averaged 75 g/fish higher weight gain and 0.12%/day greater specific growth rates than channel catfish cultured in tanks having no water velocity (P < 0.05). Channel catfish cultured at water velocities of 4 cm/second had significantly higher (P < 0.05) feed conversion efficiency and condition factor than channel catfish cultured in tanks having no water velocity. Channel catfish cultured at water velocities of 4 cm/second had significantly higher (P < 0.05) percentage carcass weight, fillet weight, and fillet moisture. The percentage visceral and fillet fat of channel catfish cultured at 4 cm/second was significantly lower (P < 0.05) than that for channel catfish raised in tanks having no water velocity. These results indicate that when cultured from initial weights of approximately 100 g to final weights exceeding 454 g in an environment having a water velocity of 4 cm/second, channel catfish have greater growth, dressout and lower fat levels than channel catfish produced in tanks having the identical water exchange rates but no water velocity.     

不同营养状况对鲫鱼偏好游泳速度的影响

为考察不同营养状况对鲤科鱼类偏好游泳速度的影响,本研究以鲫鱼(Carassius auratus)为实验对象,(25±1.0)℃条件下设置3个不同营养状况实验组:对照组(禁食48 h)、饱食组(饱食)和饥饿组(饥饿14 d),将单尾实验鱼置于梯度流速选择仪(流速范围为11.86~65.45 cm/s,等距离划分为5个流速区域,从第一到第五流速区域流速连续增加)中拍摄1 h,采用Ethovision XT9软件分析视频资料并计算实验鱼在不同流速区域平均进入频次(F,次)、单次进入停留时间(T,s/次)和平均停留时间百分比(P_t,%)等流速选择行为指标。结果显示,对照组和饱食组的F值随水流速度上升而增加,对照组的T值不同流速区域间无差异(P0.05),而饱食组第三和第四流速区域T值均显著大于其他流速区域(P0.05),因此两实验组第三和第四流速区域的P_t均显著大于其他流速区域,其偏好游泳速度为20.12~41.30 cm/s。饥饿组流速偏好行为出现表型分化,I型实验鱼在第一流速区域P_t和T值显著大于其他流速区域(P0.05),各流速区域的F值均显著小于其他实验组(P0.05),故I型实验鱼的偏好游泳速度为11.86~15.18 cm/s。而II型实验鱼则与对照组相似,在第三和第四流速区域Pt均显著大于其他流速区域(P0.05),故II型实验鱼的偏好游泳速度为20.12~41.30 cm/s。结果表明,饱食不影响鲫鱼的偏好游泳速度,可能是饱食不影响鲫鱼的游泳能力所致,但饱食组在各流速区域间的出入频次减少而停留时间有所增加。饥饿后鲫鱼偏好游泳速度出现表型分化,I型实验鱼的偏好游泳速度降低,而II型实验鱼则无明显变化,I型和II型实验鱼偏好游泳速度的差异可能是由于在饥饿条件下二者能量节约和游泳功能维持的策略不同。