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Volume 9 Issue 11
Nov.  2021
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Evaluation of suitable body size for tagging and releasing of yellowfin seabream (Acanthopagrus latus)

  • Corresponding author: WANG Xuefeng, xuefeng1999@126.com
  • Received Date: 2020-04-07
    Accepted Date: 2020-08-01
    Available Online: 2021-04-01
  • The data obtained by tag-recapture method are commonly used to evaluate the fish population dynamics and the effect of stock enhancement. However, to ensure the accuracy of the recapture data, it is necessary to choose the appropriate fish size for tagging. Acanthopagrus latus was employed to conduct two indoor experiments. In the first experiment, the effects of T-bar anchor tags on growth, survival and tag retention of A. latus from four size groups (average body length: 5 cm, 7 cm, 11 cm, and 14 cm, respectively) were examined and the size-dependent effects on survival and tag retention were tested. In the second experiment, different mix ratios of tagged fish to untagged fish from two size groups (average body length: 7 cm and 14 cm, respectively) were set for simulated catching and the catching results were resampled. The differences in catching results between groups were compared, the differences between catching result and resampling result were also compared. The results show that: ① there was no significant difference in the specific growth rate between 7 cm, 11 cm and 14 cm groups. ② the survival rate was size-dependent. All the tagged fish of 5 cm group died in the first week after tagging. The survival rate of other size groups was 77.5%, 92.5% and 100.0%, respectively. The relational expression of logistic regression between body length and the probability of survival was: P=exp(0.099X−6.900)/[1+exp(0.099X−6.900)]. ③ the tag retention rate was high (97.5% in 7 cm group, 100.0% in 11 cm and 14 cm group) but seemed to be unrelated with fish size. ④ there was no significant effect of fish size on the catching result and the resampling result but significant effect of mix ratio of tagged to untagged fish on it. In summary, it is recommended that study objectives and cost should be considered when choosing the appropriate fish size for tagging stocking fishes like A. latus. If the probability of survival needs to be >50.0%, the tagged individuals with body length should be >7 cm. If >75.0%, the body length should be >8 cm. If >95.0%, the body length should be >10 cm. And it is worth further study to know about the appropriate proportion of tagged fish for tagging and releasing.
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Evaluation of suitable body size for tagging and releasing of yellowfin seabream (Acanthopagrus latus)

    Corresponding author: WANG Xuefeng, xuefeng1999@126.com
  • 1. College of Fisheries, Guangdong Ocean University, Zhanjiang    524088, China
  • 2. Southern Marine Science and Engineering Guangdong Laboratory (Zhanjiang), Zhanjiang    524025, China

Abstract: The data obtained by tag-recapture method are commonly used to evaluate the fish population dynamics and the effect of stock enhancement. However, to ensure the accuracy of the recapture data, it is necessary to choose the appropriate fish size for tagging. Acanthopagrus latus was employed to conduct two indoor experiments. In the first experiment, the effects of T-bar anchor tags on growth, survival and tag retention of A. latus from four size groups (average body length: 5 cm, 7 cm, 11 cm, and 14 cm, respectively) were examined and the size-dependent effects on survival and tag retention were tested. In the second experiment, different mix ratios of tagged fish to untagged fish from two size groups (average body length: 7 cm and 14 cm, respectively) were set for simulated catching and the catching results were resampled. The differences in catching results between groups were compared, the differences between catching result and resampling result were also compared. The results show that: ① there was no significant difference in the specific growth rate between 7 cm, 11 cm and 14 cm groups. ② the survival rate was size-dependent. All the tagged fish of 5 cm group died in the first week after tagging. The survival rate of other size groups was 77.5%, 92.5% and 100.0%, respectively. The relational expression of logistic regression between body length and the probability of survival was: P=exp(0.099X−6.900)/[1+exp(0.099X−6.900)]. ③ the tag retention rate was high (97.5% in 7 cm group, 100.0% in 11 cm and 14 cm group) but seemed to be unrelated with fish size. ④ there was no significant effect of fish size on the catching result and the resampling result but significant effect of mix ratio of tagged to untagged fish on it. In summary, it is recommended that study objectives and cost should be considered when choosing the appropriate fish size for tagging stocking fishes like A. latus. If the probability of survival needs to be >50.0%, the tagged individuals with body length should be >7 cm. If >75.0%, the body length should be >8 cm. If >95.0%, the body length should be >10 cm. And it is worth further study to know about the appropriate proportion of tagged fish for tagging and releasing.

  • 增殖放流是人类应对近海渔业资源衰退所采取的积极措施之一,而标志放流是监测增殖放流鱼类动态和评估增殖效果的有效方法,通过回捕获得的鱼类生长、移动等信息对后续渔业资源养护与管理政策的制订具有重要意义[1-2]。标志放流需满足两个基本假设[3]:①标志对鱼的生长、死亡没有显著影响;②标志没有脱落且易识别。但这很大程度取决于标志鱼的规格,不适宜的规格易导致标志鱼死亡或标志脱落,从而影响放流群体时空分布格局分析及增殖效果评估的准确性。标志鱼的规格越大,存活率和标志保留率越高,但相应的成本也越高[4]。因此,如何权衡成本与标志效果之间的关系,在保证经济效益的前提下选取适宜的标志鱼规格,成为研究者们关注的热点。

    国内虽然已开展了许多标志对鱼类影响的评价研究[5-8],但少有关于筛选鱼类适宜标志规格方面的报道。逻辑斯蒂回归模型是对二分类因变量(即事件发生或者不发生)进行回归分析时普遍应用的定量分析方法,常用于研究某一事件发生的概率与若干因素之间的关系[9]。相较于其他回归模型,它的优点是能直接对分类的可能性进行建模,无需事先假设数据分布,避免了由于假设分布不准确所带来的问题[10]。在国外,该模型已成功用于预测不同规格标志鱼发生死亡和标志脱落的概率[11-12]。此外,基于标志鱼类回捕数据评估增殖效果的一个重要潜在假设是标志鱼与非标志鱼能够充分混合[13],但该假设的合理性及影响捕捞结果的因素尚不清楚。

    人工繁育技术的成熟为中国近海渔业资源增殖与养护提供了大量的苗种,其中黄鳍棘鲷(Acanthopagrus latus)、黑棘鲷(A. schlegelii)等鲷科(Sparidae)鱼类,因其重要的商业捕捞及休闲垂钓价值成为南海北部增殖放流的目标种[14]。本研究以黄鳍棘鲷为对象,利用目前应用较多的体外标志方法—T型标志开展两个实验,旨在分析标志鱼的存活率和标志保留率是否有规格特异性,以及不同规格、不同标志鱼比例的捕捞结果是否有差异。从而探讨适宜标志放流的鱼体规格,为后续鱼类批量化标志放流工作的科学开展提供参考依据。

1.   材料与方法
  • 实验用鱼为广东阳西县恒生水产养殖场人工培育的黄鳍棘鲷。所用T型标志设备(T型标志和标志枪)购自青岛海星仪器有限公司,T型标志为黄色,其上印有唯一的编号,全长37 mm,空气中质量0.05 g,植入鱼体内的锚定端长8 mm,直径0.8 mm。本研究分为实验1 (2017年4月1日—5月10日)和实验2(2017年6月13日),均在该养殖场内开展。

  • 按照4种规格分组,每种规格设置对照组和标志组(分别记为5 cm C、5 cm T、7 cm C、7 cm T、11 cm C、11 cm T、14 cm C和14 cm T,其中C代表对照组,T代表标志组),每组2个重复,每个重复20尾鱼,共320尾。

  • 标志前暂养:通过测量挑选符合规格的黄鳍棘鲷(平均体长5、7、11和14 cm),放入培育池中(长3 m、宽3 m、高2 m)暂养3 d以适应实验环境,期间持续增氧,投喂通用配合饲料,并及时移除死亡和行为异常的个体。实验前24 h停止喂料,以降低标志操作过程对鱼体的损伤。

    材料消毒:将T型标志和标志枪头用体积分数为75%酒精浸泡消毒5 min。

    麻醉:用丁香酚溶液(丁香酚∶酒精=1∶9,体积比,配比后溶于海水)将鱼药浴麻醉,5、7、11和14 cm规格组的麻醉剂量分别为10、20、30和40 mg/L(基于初步测试确定的剂量),待鱼体失去平衡,腹部翻转朝上时,测量全部鱼的初始体长、体质量,并记录相应的标志编号,然后进行标志(对照组每个重复随机测量10尾鱼,除不做标志处理外,其余步骤与标志组相同)。

    标志:操作人员戴上棉线手套,左手轻握鱼体,右手持标志枪,枪头与鱼体呈45°,迅速将T型标志植入背鳍基前部肌肉,未能一次性成功植入或标志时有掉落现象的鱼不用于后续实验。

    鱼体消毒:将标志鱼放入含有5%聚维酮碘溶液的海水中浸泡消毒30 min,防止标志伤口感染,消毒过程中保持充氧,使鱼复苏。

    标志后暂养:按分组将标志组和对照组暂养于装有400 L海水的玻璃钢养殖桶中(容积500 L,呈圆柱形,直径1 m,深0.9 m,底部呈半球形,有换水阀门),每桶20尾。暂养40 d,期间自然光照,水温20.0~27.8 °C,盐度24.1~28.6,pH值7.50~8.22,溶解氧含量大于7.00 mg/L。每天换水1次(换水量50%),饱食投喂2次(上午9:00、下午5:00);每8 h观察并记录鱼的死亡、脱标等情况,同时测量死亡鱼的体长、体质量,记录相应的标志编号)。为减少误差,标志操作及数据测定均由2名受过培训的实验员完成。

  • 按照2种规格分组[小规格组的平均体长(7.41±0.61) cm、大规格组的平均体长(14.66±0.94) cm],每种规格按标志鱼与非标志鱼的混合比例分为5个实验组(即标志鱼占比分别为5%、10%、20%、40%和80%),2种规格共10个实验组。

  • 标志鱼处理:参照实验1的标志操作步骤对鱼进行标志,标志后暂养3 d再开展捕捞实验。

    分组:各组分别按照相应的规格和比例,将标志鱼与非标志鱼混合放入装有300 L水的玻璃钢水桶中(桶的形状、规格同实验1)。

    随机捕捞:由同一人负责用手抄网(捞网的部分呈圆形,直径40 cm,圆锥形网兜深20 cm,网目2 mm,手抄杆的部分长50 cm)沿着桶的左侧深入桶底后往右侧迅速捞取,每组有放回的随机捕捞3次,每次间隔5 min(间隔期间持续充氧,正式捕捞时不充氧)。记录每次捞取的鱼中标志鱼及非标志鱼的数量。

  • 实验数据均以每组2个重复的平均值表示。实验结束后停食24 h,每桶随机取10尾鱼测量终末体长、体质量并记录相应的标志编号(对照组的鱼无对应编号),基于该编号,可以在个体基础上分析标志鱼的生长情况,按以下公式计算特定生长率[15](specific growth rate,SGR,%/d):

    式中,W0Wt分别为初始体质量(g)和终末体质量(g),t为实验天数(d)。

    采用单因素方差分析(One-Way ANOVA)比较各规格标志组的特定生长率与对照组之间是否存在显著差异。显著性水平设为0.05。

    将各标志组的每尾编号鱼发生死亡的赋值为0,存活的赋值为1,通过R软件(v3.6.3),采用逻辑斯蒂回归模型分别拟合标志鱼存活概率和标志保留概率与初始体长的关系。逻辑斯蒂回归关系式[10]

    式中,P为存活概率或标志保留概率(%),b0b1为估计参数,X为初始体长(cm)。

  • 捕捞结果用捞取的标志鱼尾数占总捞取尾数的百分比表示。利用卡方检验(chi-square tests)比较各组捕捞结果与实验原设置比例之间的差异,并比较各组间捕捞结果的差异[16]

    利用R软件中的sample函数进行计算机重抽样(resampling),各组分别从3次捕捞结果中随机抽取1 000次(有放回),得出计算机重抽样的1 000次结果。并用卡方检验比较各组捕捞结果和重抽样结果之间是否具有显著差异。二者若无显著差异,说明捕捞结果符合随机分布,3次重复捕捞已能够较好地反映总体;若有显著差异,说明捕捞结果不符合随机分布,3次重复捕捞结果不足以反映总体,需要增加重复捕捞次数[17]

2.   结果
  • 标志对黄鳍棘鲷生长的影响不显著(P>0.05)。实验前后各组鱼的体长、体质量和特定生长率的变化见表1,其中5 cm T组的鱼在标志后7 d内全部死亡,无法计算其生长指标。单因素方差分析结果表明各规格标志组的特定生长率与对照组之间无显著差异(P>0.05)。

    组别
    groups
    初始体长/cm
    initial body length
    终末体长/cm
    final body length
    初始体质量/g
    initial body weight
    终末体质量/g
    final body weight
    特定生长率/(%/d)
    SGR
    存活率/%
    survival rate
    标志保留率/%
    tag retention rate
    5 cm C5.06±0.486.92±0.313.96±1.019.86±1.002.3582.5
    5 cm T5.05±0.413.87±0.980
    7 cm C7.25±0.398.83±0.4211.19±1.5921.05±2.731.5897.5
    7 cm T7.22±0.438.78±0.3811.24±1.8620.75±2.401.5577.597.5
    11 cm C11.89±0.4612.95±0.4250.96±7.0674.35±6.740.96100.0
    11 cm T11.87±0.5012.89±0.4849.03±6.9972.36±8.060.9892.5100.0
    14 cm C14.07±0.3714.96±0.4974.00±5.7186.10±8.270.37100.0
    14 cm T14.04±0.4514.92±0.4374.19±8.6786.75±6.150.40100.0100.0
    注:“—”表示无此项数据,C. 对照组,T. 标志组
    Notes: “—”means no such data, C. control group, T. tagged group

    Table 1.  Growth indices, survival rate and tag retention rate in each group

  • 标志鱼的存活率具有规格特异性,与鱼的体长成正比(表1)。5 cm T组的鱼在标志后第1天死亡率达65.0%,7 d内死亡率为100.0%。拟合标志鱼存活概率与初始体长的关系,得其回归关系式为P=exp(0.099X−6.900)/[1+exp(0.099X−6.900)]。由逻辑斯蒂回归模型可以看出,标志鱼的初始体长大于7 cm,存活概率高于50.0%;初始体长大于8 cm,存活概率高于75.0%;初始体长大于10 cm,存活概率高于95.0%(图1)。

    Figure 1.  Relationship between probability of survival and initial body length of A. latus

    各规格标志组的标志保留率较高(均高于97.5%),但与初始体长无明显关系,不存在规格特异性(表1)。7、11和14 cm T组的标志保留率分别为97.5%、100.0%和100.0%,实验过程中仅7 cm T组在标志后第1天发现1个标志脱落。

  • 捕捞结果不受鱼体规格的影响,但受标志鱼比例的影响极显著。卡方检验结果表明,各组捕捞结果与原设置比例之间无显著差异(P>0.05),即标志鱼与不标志鱼能够充分混合。同一比例条件下,不同规格组的捕捞结果无显著差异(P>0.05)。同一规格条件下,不同比例组之间的捕捞结果有极显著差异(P<0.01),标志鱼数量占比越高,其捕捞结果越大(图2)。

    Figure 2.  Result of simulated catching

    重抽样结果亦不受鱼体规格的影响,但受标志鱼的比例影响极显著。各组的重抽样结果与捕捞结果基本重叠(图3),二者无显著差异(P>0.05)。即捕捞结果符合随机分布,3次重复捕捞结果能较好地反映总体。

    Figure 3.  Result of resampling

3.   讨论
  • 实验鱼的特定生长率、存活率和标志保留率是常用于定量评价标志产品对鱼类影响的重要指标[18]。在鱼的生长方面,本研究发现各规格标志组和对照组的特定生长率无显著差异,表明标志对不同规格实验鱼的生长无显著的负面影响,这与大部分鱼类标志影响研究的结论一致[19-22]。在鱼的存活方面,5 cm C组鱼的存活率明显高于5 cm T组,5 cm T组鱼在标志后7 d内全部死亡,可能由于:①标志部位肌肉厚度不够,标志时枪头易刺到鱼体内部骨骼致死。②小规格鱼的抗压能力较弱,无法承受标志过程的压力及标志本身对鱼体产生的胁迫。柳学周等[23]报道过全长为5 cm的半滑舌鳎(Cynoglossus semilaevis)苗种在应用T型标志后3 d内全部死亡,认为小规格的苗种不适合使用T型标志。刘芝亮等[24]在牙鲆(Paralichthys olivaceus)苗种的标志研究中也得到类似的结论。本研究中7 cm T组的存活率(77.5%)<11 cm T组(92.5%)<14 cm T组(100%),存活率随体长的增加而增加,即标志鱼的存活率存在规格特异性。Lin等[4]研究CWT标志对不同规格蒙古鲌(Culter mongolicus)的影响后亦有此结论。在鱼的标志保留方面,本研究中各组的标志保留率均较高,与规格没有明显的关系,不存在规格特异性。黄国光等[25]利用“工”型塑料牌开展研究时亦发现黄鳍棘鲷的规格对标志保留率无影响。而Pennock等[12]研究南方红腹雅罗鱼(Chrosomus erythrogaster)时发现应用PIT标志的保留率与标志鱼的规格成正比。可能原因是本研究所用的T型标志较易固定以及所选标志部位肌肉较厚实,标志一经植入不易脱落,不因鱼体规格而有差异。

  • 本研究捕捞结果中标志鱼的百分比与实验预设标志鱼的百分比没有显著差异,说明标志鱼没有因标志而较易或较难被捕捞,标志鱼与不标志鱼能够充分混合。各规格组的捕捞结果没有显著差异,表明标志鱼规格不是影响标志鱼回捕结果的主要因素,因此无须特意放流过大的标志鱼来保证二者充分混合,避免因此增加成本。

    本研究中的逻辑斯蒂回归模型可用于指导研究人员依据预测的标志鱼存活概率来选择相应的规格或依据标志鱼的规格来预测存活概率,为合理选取标志鱼规格提供新思路。结合本研究的结果,建议今后开展相关研究时,应综合考虑成本及可接受的误差范围,选取符合实验目的的鱼体规格开展标志放流研究。若要保证标志鱼的存活概率高于50%,则体长至少为7 cm;高于75%则体长至少为8 cm;高于95%则体长至少为10 cm。

    此外,捕捞实验结果表明,标志鱼的比例是影响标志鱼回捕结果的主要因素,标志鱼的比例越高,回捕结果越大。因此建议在成本允许的条件下,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。目前,开展鲷科鱼类标志放流时,标志鱼的数量一般占总增殖放流鱼数量的1%以上,且最少为3 000尾[26],但具体科学的标志比例有待进一步研究。本研究所用苗种规格梯度受限于当季苗种条件,无法获得更为理想的规格,今后若进一步开展其他鱼类的标志放流适宜规格评价研究,建议细化体长组梯度,并增加样本数量,以优化逻辑斯蒂模型。

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