Edwine Yongo, Simon W. Agembe, Julius O. Manyala, Edna Waithaka
{"title":"奈瓦沙湖尼罗罗非鱼、紫鳞罗非鱼和白罗非鱼的生物学和种群结构研究","authors":"Edwine Yongo, Simon W. Agembe, Julius O. Manyala, Edna Waithaka","doi":"10.1111/lre.12398","DOIUrl":null,"url":null,"abstract":"<p>The Nile tilapia (<i>Oreochromis niloticus</i>), Redbelly tilapia (<i>Coptodon zillii</i>) and Blue spotted tilapia (<i>Oreochromis leucostictus</i>) were introduced into Lake Naivasha in the 1950s to diversify and boost the lake fisheries. These species have since been exploited in the commercial gillnet fishery. The fish stocks, however, are currently facing problems of pollution, wetland degradation and intense fishing pressures. Accordingly, the present study investigated some aspects of the biology and population structure of the three tilapiine species in light of changing lake conditions. Fish samples were collected from January to December 2019 using multifilament gillnets of 2.0-to-6.0-inch mesh sizes. Immediately after their capture, the fish specimens were transported to the lab for morphometric measurements and analysis of maturity. The highest and lowest mean (±SD) total length (TL) were exhibited by <i>O</i>. <i>niloticus</i> (22.9 ± 5.2 cm) and <i>C</i>. <i>zillii</i> (14.5 ± 2.1 cm), respectively. Similarly, <i>O</i>. <i>niloticus</i> exhibited a higher mean weight (268.4 ± 18.0 g) and body depth (7.6 ± 2.5 cm), compared to the other species. <i>O</i>. <i>niloticus</i> exhibited an isometric growth pattern, while <i>C</i>. <i>zillii</i> and <i>O</i>. <i>leucostictus</i> exhibited negative allometric growth. The fish species were in good condition, with mean condition factors of 1.59 ± 0.07, 1.51 ± 0.06 and 1.23 ± 0.03 for <i>C</i>. <i>zillii</i>, <i>O</i>. <i>leucostictus</i> and <i>O</i>. <i>niloticus</i>, respectively. Furthermore, the condition factors for <i>O</i>. <i>leucostictus</i> and <i>O</i>. <i>niloticus</i> varied by size class, exhibiting a decreasing trend with increased fish size. The male:female sex ratio revealed significantly more males than females for <i>O</i>. <i>niloticus</i> (2.30:1.0) and <i>O</i>. <i>leucostictus</i> (2.36:1.0), although not for <i>C</i>. <i>zillii</i> (1.15:1.0). <i>O</i>. <i>niloticus</i> (28.0–29.0 cm TL) matured at a larger size, followed by <i>O</i>. <i>leucostictus</i> (21.0–26.0 cm TL), and <i>C</i>. <i>zillii</i> (15.0–17.0 cm TL). In comparison, values of length-weight parameters, condition factor, sex ratio and size at first maturity of the studied fishes varied in Lake Naivasha, Victoria, Albert and George. The gillnet mesh ≤3.0″ mainly targeted small-sized immature fish, while mesh ≥4″ targeted mature fish, particularly <i>O</i>. <i>niloticus</i>. It was concluded that gillnets with ≥4.0″ mesh could safely be applied for this fishery in Lake Naivasha, whereas the use of smaller mesh should be controlled to protect the juveniles as a means of maintaining sustainable fisheries. Furthermore, the present study also provided useful information, including size at maturity that is vital for setting mesh size for managing the lake fishery.</p>","PeriodicalId":39473,"journal":{"name":"Lakes and Reservoirs: Research and Management","volume":"27 1","pages":""},"PeriodicalIF":0.0000,"publicationDate":"2022-03-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/lre.12398","citationCount":"1","resultStr":"{\"title\":\"Aspects of the biology and population structure of Oreochromis niloticus, Coptodon zillii and Oreochromis leucostictus tilapia in Lake Naivasha, Kenya\",\"authors\":\"Edwine Yongo, Simon W. Agembe, Julius O. Manyala, Edna Waithaka\",\"doi\":\"10.1111/lre.12398\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<p>The Nile tilapia (<i>Oreochromis niloticus</i>), Redbelly tilapia (<i>Coptodon zillii</i>) and Blue spotted tilapia (<i>Oreochromis leucostictus</i>) were introduced into Lake Naivasha in the 1950s to diversify and boost the lake fisheries. These species have since been exploited in the commercial gillnet fishery. The fish stocks, however, are currently facing problems of pollution, wetland degradation and intense fishing pressures. Accordingly, the present study investigated some aspects of the biology and population structure of the three tilapiine species in light of changing lake conditions. Fish samples were collected from January to December 2019 using multifilament gillnets of 2.0-to-6.0-inch mesh sizes. Immediately after their capture, the fish specimens were transported to the lab for morphometric measurements and analysis of maturity. The highest and lowest mean (±SD) total length (TL) were exhibited by <i>O</i>. <i>niloticus</i> (22.9 ± 5.2 cm) and <i>C</i>. <i>zillii</i> (14.5 ± 2.1 cm), respectively. Similarly, <i>O</i>. <i>niloticus</i> exhibited a higher mean weight (268.4 ± 18.0 g) and body depth (7.6 ± 2.5 cm), compared to the other species. <i>O</i>. <i>niloticus</i> exhibited an isometric growth pattern, while <i>C</i>. <i>zillii</i> and <i>O</i>. <i>leucostictus</i> exhibited negative allometric growth. The fish species were in good condition, with mean condition factors of 1.59 ± 0.07, 1.51 ± 0.06 and 1.23 ± 0.03 for <i>C</i>. <i>zillii</i>, <i>O</i>. <i>leucostictus</i> and <i>O</i>. <i>niloticus</i>, respectively. Furthermore, the condition factors for <i>O</i>. <i>leucostictus</i> and <i>O</i>. <i>niloticus</i> varied by size class, exhibiting a decreasing trend with increased fish size. The male:female sex ratio revealed significantly more males than females for <i>O</i>. <i>niloticus</i> (2.30:1.0) and <i>O</i>. <i>leucostictus</i> (2.36:1.0), although not for <i>C</i>. <i>zillii</i> (1.15:1.0). <i>O</i>. <i>niloticus</i> (28.0–29.0 cm TL) matured at a larger size, followed by <i>O</i>. <i>leucostictus</i> (21.0–26.0 cm TL), and <i>C</i>. <i>zillii</i> (15.0–17.0 cm TL). In comparison, values of length-weight parameters, condition factor, sex ratio and size at first maturity of the studied fishes varied in Lake Naivasha, Victoria, Albert and George. The gillnet mesh ≤3.0″ mainly targeted small-sized immature fish, while mesh ≥4″ targeted mature fish, particularly <i>O</i>. <i>niloticus</i>. It was concluded that gillnets with ≥4.0″ mesh could safely be applied for this fishery in Lake Naivasha, whereas the use of smaller mesh should be controlled to protect the juveniles as a means of maintaining sustainable fisheries. Furthermore, the present study also provided useful information, including size at maturity that is vital for setting mesh size for managing the lake fishery.</p>\",\"PeriodicalId\":39473,\"journal\":{\"name\":\"Lakes and Reservoirs: Research and Management\",\"volume\":\"27 1\",\"pages\":\"\"},\"PeriodicalIF\":0.0000,\"publicationDate\":\"2022-03-03\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"https://onlinelibrary.wiley.com/doi/epdf/10.1111/lre.12398\",\"citationCount\":\"1\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Lakes and Reservoirs: Research and Management\",\"FirstCategoryId\":\"1085\",\"ListUrlMain\":\"https://onlinelibrary.wiley.com/doi/10.1111/lre.12398\",\"RegionNum\":0,\"RegionCategory\":null,\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q3\",\"JCRName\":\"Environmental Science\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Lakes and Reservoirs: Research and Management","FirstCategoryId":"1085","ListUrlMain":"https://onlinelibrary.wiley.com/doi/10.1111/lre.12398","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q3","JCRName":"Environmental Science","Score":null,"Total":0}
引用次数: 1
摘要
尼罗罗非鱼(Oreochromis niloticus)、红肚罗非鱼(Coptodon zillii)和蓝斑罗非鱼(Oreochromis leucosttictus)在20世纪50年代被引入奈瓦沙湖,以使湖泊渔业多样化和发展。这些物种已被用于商业刺网渔业。然而,鱼类资源目前正面临污染、湿地退化和巨大捕捞压力的问题。因此,本研究对三种罗非鱼在变化的湖泊条件下的生物学和种群结构进行了研究。2019年1月至12月,使用2.0至6.0英寸网目尺寸的多丝刺网采集鱼类样本。捕获后,鱼标本立即被运送到实验室进行形态测量和成熟度分析。平均总长度(TL)最高的是niloticus(22.9±5.2 cm),最低的是cillii(14.5±2.1 cm)。与其他物种相比,niloticus的平均体重(268.4±18.0 g)和体深(7.6±2.5 cm)均高于其他物种。niloticus呈等长生长模式,而C. zillii和O. leucostictus呈负异速生长模式。鱼种状况良好,平均条件因子分别为1.59±0.07、1.51±0.06和1.23±0.03。不同鱼种的条件因子差异较大,随鱼种大小的增加呈下降趋势。雌雄比显示,niloticus(2.30:1.0)和leucostictus(2.36:1.0)的雌雄比显著高于雌性,而zillii(1.15:1.0)的雌雄比不显著高于雌性。niloticus (28.0 ~ 29.0 cm TL)成熟期较大,其次为O. leucosttictus (21.0 ~ 26.0 cm TL)和C. zillii (15.0 ~ 17.0 cm TL)。相比之下,奈瓦沙湖、维多利亚湖、阿尔伯特湖和乔治湖所研究鱼类的长重参数、条件因子、性别比和初成熟时的大小值各不相同。刺网目目≤3.0″主要针对小型未成熟鱼,目目≥4″主要针对成熟鱼,尤其是尼罗鳉鱼。结论认为,≥4.0″网目刺网可安全用于奈瓦沙湖的捕捞,但应控制较小网目刺网的使用,以保护幼鱼,维持渔业的可持续发展。此外,本研究还提供了有用的信息,包括成熟时的尺寸,这对于设置湖泊渔业管理的网目尺寸至关重要。
Aspects of the biology and population structure of Oreochromis niloticus, Coptodon zillii and Oreochromis leucostictus tilapia in Lake Naivasha, Kenya
The Nile tilapia (Oreochromis niloticus), Redbelly tilapia (Coptodon zillii) and Blue spotted tilapia (Oreochromis leucostictus) were introduced into Lake Naivasha in the 1950s to diversify and boost the lake fisheries. These species have since been exploited in the commercial gillnet fishery. The fish stocks, however, are currently facing problems of pollution, wetland degradation and intense fishing pressures. Accordingly, the present study investigated some aspects of the biology and population structure of the three tilapiine species in light of changing lake conditions. Fish samples were collected from January to December 2019 using multifilament gillnets of 2.0-to-6.0-inch mesh sizes. Immediately after their capture, the fish specimens were transported to the lab for morphometric measurements and analysis of maturity. The highest and lowest mean (±SD) total length (TL) were exhibited by O. niloticus (22.9 ± 5.2 cm) and C. zillii (14.5 ± 2.1 cm), respectively. Similarly, O. niloticus exhibited a higher mean weight (268.4 ± 18.0 g) and body depth (7.6 ± 2.5 cm), compared to the other species. O. niloticus exhibited an isometric growth pattern, while C. zillii and O. leucostictus exhibited negative allometric growth. The fish species were in good condition, with mean condition factors of 1.59 ± 0.07, 1.51 ± 0.06 and 1.23 ± 0.03 for C. zillii, O. leucostictus and O. niloticus, respectively. Furthermore, the condition factors for O. leucostictus and O. niloticus varied by size class, exhibiting a decreasing trend with increased fish size. The male:female sex ratio revealed significantly more males than females for O. niloticus (2.30:1.0) and O. leucostictus (2.36:1.0), although not for C. zillii (1.15:1.0). O. niloticus (28.0–29.0 cm TL) matured at a larger size, followed by O. leucostictus (21.0–26.0 cm TL), and C. zillii (15.0–17.0 cm TL). In comparison, values of length-weight parameters, condition factor, sex ratio and size at first maturity of the studied fishes varied in Lake Naivasha, Victoria, Albert and George. The gillnet mesh ≤3.0″ mainly targeted small-sized immature fish, while mesh ≥4″ targeted mature fish, particularly O. niloticus. It was concluded that gillnets with ≥4.0″ mesh could safely be applied for this fishery in Lake Naivasha, whereas the use of smaller mesh should be controlled to protect the juveniles as a means of maintaining sustainable fisheries. Furthermore, the present study also provided useful information, including size at maturity that is vital for setting mesh size for managing the lake fishery.
期刊介绍:
Lakes & Reservoirs: Research and Management aims to promote environmentally sound management of natural and artificial lakes, consistent with sustainable development policies. This peer-reviewed Journal publishes international research on the management and conservation of lakes and reservoirs to facilitate the international exchange of results.