The ecological characteristics of four lizardfishes, Trachinocephalus myops, Saurida undosquamis, Saurida tumbil and Saurida elongata, were studied from specimens （910 T. myops, 454 S. un-dosquamis, 686 S. tumbil and...The ecological characteristics of four lizardfishes, Trachinocephalus myops, Saurida undosquamis, Saurida tumbil and Saurida elongata, were studied from specimens （910 T. myops, 454 S. un-dosquamis, 686 S. tumbil and 744 S. elongata） collected monthly in the southern Taiwan Straits from April 2005 to March 2006. The population dynamics of the four lizardfishes was also discussed by the comparison with the previous studies. All being composed of 7 a classes; the dominant group of T. myops and S. tumbil was 1–2 a, while S. undosquamis and S. elongate were 2–3 a. The total mortality coefficient Z and the fishing mortality F were at high as indicated by the exploitation ratio E（0.5）, and a large number of by-caught juvenile and young fishes showing that the stock of lizardfishes in this area was overexploited and the fishing gear was irrational. Compared with the previous studies, the maximum and mean fork length, body mass and age of the four lizard- fishes declined gradually, the lizardfishes populations were younger in age and smaller in size. The asymptotic fork length L ∞ decreased while increasing growth coefficient k, and age at the inflexion point of mass t r was younger compared with the previous studies. The declining of older ones has moderated the feeding competition and the younger ones grew faster. The larger mortality param-eters Z, M and F have revealed higher fishing pressure. The smaller change of the first mature fork length of female T . myops and the change from K selection pattern to r selection pattern of S. tumbil have indicated a more vulnerable fishery ecosystem in this area. The changes of ecological characteristics and population dynamics may be caused by over-exploitation of demersal fishes such as the lizardfishes, especially a large number of juvenile and young fishes by-catch by the current fishing gears and methods. Therefore, in addition to the traditional fishery management approach such as the minimum length-limit, ecosystem approach to fisheries management （EAF） should be taken to improve the practical marine ecosystem management, including increased fishing intensity of the non-economic species especially the feeding competitors of the lizardfishes and the conservation of the pelagic fishery population in the fisheries ecosystem, in order to restore the fishery population and achieve the sustainable use of the fishery stocks.展开更多
A fuzzy mathematical method is used to discriminate the similarities of pelagic fishes land- ed in the 9180 hauls by 10 light-seine information vessels in the southern Fujian waters from 1989 to 1998. The results indi...A fuzzy mathematical method is used to discriminate the similarities of pelagic fishes land- ed in the 9180 hauls by 10 light-seine information vessels in the southern Fujian waters from 1989 to 1998. The results indicate that the dominant species of the communities had an obvious alternation and the fuzzy adjacency of annual species composition varied between 0. 659 and 0. 923 with an average value of 0. 791. The fuzzy clustering analysis indicates that the annual fuzzy adjacency in general remains good although the species composition of the pelagic fishes has changed to a certain degree since 1992. This paper concludes that the community structure of pelagic fishes in the southern Taiwan Strait remains rel- atively stable and the state of fish stocks shows a good potentiality for a larger utilization.展开更多
基金Marine Public Welfare Project of China under contract Nos 200805065,200905019-6,200705029 and 200805064Chinese Off shore Investigation and Assessment under contract No.908-02-04008+1 种基金the Scientific Research Foundation of the Third Institute of Oceanography,SOA under contract No.2011006Marine Science Foundation for Young Scientist under contract No.2011143
文摘The ecological characteristics of four lizardfishes, Trachinocephalus myops, Saurida undosquamis, Saurida tumbil and Saurida elongata, were studied from specimens （910 T. myops, 454 S. un-dosquamis, 686 S. tumbil and 744 S. elongata） collected monthly in the southern Taiwan Straits from April 2005 to March 2006. The population dynamics of the four lizardfishes was also discussed by the comparison with the previous studies. All being composed of 7 a classes; the dominant group of T. myops and S. tumbil was 1–2 a, while S. undosquamis and S. elongate were 2–3 a. The total mortality coefficient Z and the fishing mortality F were at high as indicated by the exploitation ratio E（0.5）, and a large number of by-caught juvenile and young fishes showing that the stock of lizardfishes in this area was overexploited and the fishing gear was irrational. Compared with the previous studies, the maximum and mean fork length, body mass and age of the four lizard- fishes declined gradually, the lizardfishes populations were younger in age and smaller in size. The asymptotic fork length L ∞ decreased while increasing growth coefficient k, and age at the inflexion point of mass t r was younger compared with the previous studies. The declining of older ones has moderated the feeding competition and the younger ones grew faster. The larger mortality param-eters Z, M and F have revealed higher fishing pressure. The smaller change of the first mature fork length of female T . myops and the change from K selection pattern to r selection pattern of S. tumbil have indicated a more vulnerable fishery ecosystem in this area. The changes of ecological characteristics and population dynamics may be caused by over-exploitation of demersal fishes such as the lizardfishes, especially a large number of juvenile and young fishes by-catch by the current fishing gears and methods. Therefore, in addition to the traditional fishery management approach such as the minimum length-limit, ecosystem approach to fisheries management （EAF） should be taken to improve the practical marine ecosystem management, including increased fishing intensity of the non-economic species especially the feeding competitors of the lizardfishes and the conservation of the pelagic fishery population in the fisheries ecosystem, in order to restore the fishery population and achieve the sustainable use of the fishery stocks.
基金This project is funded by the Fujian Department of Fisheries (Min Shui Ke 1998-08).
文摘A fuzzy mathematical method is used to discriminate the similarities of pelagic fishes land- ed in the 9180 hauls by 10 light-seine information vessels in the southern Fujian waters from 1989 to 1998. The results indicate that the dominant species of the communities had an obvious alternation and the fuzzy adjacency of annual species composition varied between 0. 659 and 0. 923 with an average value of 0. 791. The fuzzy clustering analysis indicates that the annual fuzzy adjacency in general remains good although the species composition of the pelagic fishes has changed to a certain degree since 1992. This paper concludes that the community structure of pelagic fishes in the southern Taiwan Strait remains rel- atively stable and the state of fish stocks shows a good potentiality for a larger utilization.
