共查询到20条相似文献，搜索用时 15 毫秒
1.
J. S. Pet G. J. M. Gevers W. L. T. Van Densen J. Vijverberg 《Ecology of Freshwater Fish》1996,5(1):1-14
Abstract– Stock dynamics of the introduced tilapia Oreochromis mossambicus and co-occurring indigenous cyprinids were studied in a typical lowland reservoir in Sri Lanka. All species exhibited peaks in reproductive activity during the rainy seasons in November and May. O. mossambicus was estimated to grow to 14 cm in its first year and to 21 cm in its second. A high natural mortality ( M was found, both for the cyprinids ( M =1.3 yr−1 to 4.7 yr−1 over a range of species) and for O. mossambicus ( M = 1.9 yr−l and 1.7 yr−1 for females and males). The fishing mortality ( F ) of O. mossumbicus , estimated for the length range from 15.0 to 18.5 cm, was 5.5 yr−1 for females and 4.7 yr−1 for males. The total fish biomass was estimated at 1 829 kg/ha, with 128 kg/ha O. mossambicus and 1 098 kg/ha small pelagic cyprinids, mainly Amblypharyngodon melettinus . The total biological fish production was around 5 400 kg/ha/yr, with O. mossambicus and the small pelagic cyprinids accounting for 400 kg/ha/yr and 3 600 kg/ha/yr respectively. The commercial fishery yielded 242 kg/ha/yr (including 70% or 169 kg/ha/yr O. mossambicus ), indicating an incomplete utilization of the total biological fish production. It was concluded that there is scope for an approximately 100% increase of the total yield. Reimplementation of a 76 mm minimum mesh size, to prevent overfishing of O. mossambicus , is recommended as a management measure. Additional options are direct exploitation of the untapped resource of small pelagic cyprinids, or indirect exploitation by means of a culture-based fishery on Lates calcarifer , a controllable predator. 相似文献
2.
山东近海口虾蛄单位补充量渔获量评估 总被引：2，自引：1，他引：1
为完善口虾蛄的基础生物学资料,并为口虾蛄资源的管理提供科学指导和理论依据,本研究根据2016至2017年山东近海渔业资源底拖网调查获得的口虾蛄体长、体质量数据,估算了口虾蛄的生长、死亡参数,构建了基于体长结构的单位补充量渔获量(YPR)模型,研究口虾蛄的资源动态和管理策略。采集调查口虾蛄样品共5028尾,体长—体质量关系的表达式为W=0.0145L2.88,为负异速生长;使用ELEFAN方法估算出口虾蛄的渐进体长L∞为19.87 cm,生长速率K为0.62 a−1。口虾蛄的生长表现出明显的季节性变化规律,生长参数的季节振幅C为0.76,10月份生长最快,4月份生长最慢。通过体长转换的渔获曲线估算出口虾蛄的总死亡系数Z为3.24 a−1,根据不同方法估算自然死亡系数M的范围为0.75~1.27 a−1,捕捞死亡系数F的估算范围为1.96~2.49 a−1,开发率的均值为0.67。YPR模型结果显示,随着F增大,YPR值呈现先上升后下降的趋势,生物学参考点F0.1和Fmax的值分别为0.92a−1和1.88a−1。口虾蛄资源处于过度开发的状态,应降低捕捞压力,同时调整开捕体长,以维持口虾蛄渔业资源量和渔获量。 相似文献
3.
S. S. DE SILVA 《Aquaculture Research》1985,16(3):265-272
Abstract. The fishery of Parakrama Samudra, an ancient man-made lake of 2662 ha in Sri Lanka (8°-10°N; 80°-82°E), as in most other man-made reservoirs in the island, is dominated by the exotic cichlid Sarotherodon mossambicus (Peters), introduced in 1952. The fluctuations in catch per unit/fisherman over the period 1960 to 1982 are shown to be dependent on the yearly fluctuations in the water-level, the changes in the water-level effects being manifested in the fishery after a period of 3 years. The above results were arrived at by auto-correlation analysis of yearly catch per unit effort against the fluctuation of the water level at the main sluice. The changes in yield in a particular year are correlated to the changes in the water level and are described by the equation;
where Y = yield in kg fisherman-1 month-1 in year t and X = fluctuations in the water-level in year t - 3. The available growth rates in natural and semi-natural impoundments also indicate that the size at which S. mossambicus enter the fishery in Parakrama Samudra corresponds to their size in the third year of life (age 2+). The significance of the above observations is discussed on the basis of available knowledge on the reproductive cycle and the nesting requirements of S. mossambicus which are achieved when significant fluctuations in the reservoir level take place by making available optimal water depths in areas with a suitable substratum. The possible use of the above criteria as a management measure is also briefly discussed in the light of possible irrigational and fisheries conflicts in the utilization of the reservoir resources. 相似文献
where Y = yield in kg fisherman
4.
S. S. DE SILVA 《Aquaculture Research》1985,16(1):91-102
Abstract. The inland fishery in Sri Lanka (6–10°N; 79–82°E) is essentially a fishery confined to man-made lakes and is dominated by the introduced cichlid Sarotherodon mossambicus (Peters). Catch statistics of 20 such major reservoirs indicate that the yield of this species ranges from 64·0 to 918 kg per ha and accounts for between 56 and 99% of the total yield in individual reservoirs. The yield of S. mossambicus is closely related to the fishing pressure exerted. Catch/effort data from the individual reservoir fisheries when analysed collectively simulate changes in a single large fishery. In the fishery the relationship of yield to effort is described by the equation: Y = 4·OX – 53·8X ( r = 0·92; P < 0·001), where Y = yield in kg per ha per annum and X = number of craft-days per ha per annum, indicating that the reservoirs in Sri Lanka remain underfished. However, very high increases in fishing pressure in two reservoirs, for which data are available over a 5-year period, indicate that the increases have resulted in a significant decline in the catch per unit effort. The reasons for the success of the S. mossambicus fishery in individual reservoirs, and also simulation of features of a single large fishery in reservoirs, with widely different hydrological and limnological regimes, are discussed in qualitative terms. It is hypothesized that the abundance is determined by factors other than food availability. Fresh management strategies to optimize the fishery from the point of view of optimal fishing pressure permissible from the present analysis are suggested. 相似文献
5.
It is important to consider the potential effectiveness of regulations for reducing total harvest levels when developing fishery management plans. A random forest (RF) modelling approach was used to examine how changing per‐angler harvest or minimum size limit regulations affected sport fishery harvest in US Atlantic coast recreational fisheries. Harvest limits per angler (i.e. bag limits) were typically high initially and subsequently reduced, whereas almost half of minimum length limits were initially below the length‐at‐maturity and subsequently increased. Across most fisheries examined, extreme reductions in harvest limits (e.g. from unlimited to catch‐and‐release) were largely ineffective at limiting total fishery harvest. Increasingly restrictive minimum length limits caused a greater average harvest reduction than per‐angler harvest limits. Some regulation changes were associated with higher angling effort and thus increased harvest, which suggests that when effort cannot be constrained, more direct harvest limitations should be considered. 相似文献
6.
M. H. HOLLEY & M. J. MACEINA M. THOMÉ-SOUZA B. R. FORSBERG 《Fisheries Management and Ecology》2008,15(2):93-98
Abstract The middle portion of the Rio Negro River in Brazil near the equator supports a popular recreational sport fishery for speckled peacock bass, Cichla temensis (Humboldt). The objective of this study was to determine the effect of fishing mortality on this population. Fish were collected from sport-fishing ( n = 72) and commercial ( n = 103) catches and otoliths were aged to estimate longevity, growth and natural mortality. Recreational anglers in this region seek to catch, then release, larger speckled peacock bass; and fish larger than 62 cm standard length (SL) (about 4.5 kg) served as a bench mark to assess the potential impact of subsistence and commercial harvest on the abundance of larger fish in the sport fishery. Time of opaque band formation on otoliths generally coincided with the dry season (November to April); these bands appeared to form once per year, but formation was highly variable. Speckled peacock bass grew to 62 cm SL on average in 6.4 years, but some fish obtained this size in 4–5 years. Maximum age was 9 years, but most fish were less than 7 years. Instantaneous annual natural mortality ( M ) estimated from maximum size, longevity and growth ranged from 0.19 to 0.44. Simulation modelling predicted that exploitation rates of fish >25 cm SL similar to the estimated natural mortality rates would reduce the abundance of fish >62 cm by 67–89% compared with no harvest. Even modest exploitation rates of 5% and 10% would result in approximately 30–50% reduction, respectively, of these larger fish. Abundance of large speckled peacock bass that sustains the sport fishery is susceptible to low rates of exploitation in this remote region of Brazil. 相似文献
7.
Abstract In January 2004, 46 wels catfish, Silurus glanis L., between 51 and 135 cm total length were tagged and released into a 0.4 ha recreational, catch and release, lake fishery in the UK, and their recapture by anglers monitored throughout the year. Of the 46 tagged fish, 16 were recaptured by anglers during 170 capture events. Some individual fish were captured up to 26 times. Catfish <75 cm appeared to be the least susceptible to capture and fish >100 cm most susceptible. Frequency of captures increased with temperatures >10 °C and peaked between June and August. Selected recapture weight data were used to produce a mass specific growth equation and revealed specific growth rate was a decreasing function of body mass over the size range of the recaptured fish. Their growth was slower than fish from elsewhere in their distribution range. 相似文献
8.
Eiji Tanaka 《Fisheries Science》2014,80(6):1129-1144
The paper compiles a catch history of Japanese eels Anguilla japonica in East Asia and some Japanese relative abundance series. Maximum likelihood estimates of stock abundance of eels have been obtained using the abundance series and various biological parameters, such as growth, maturity and natural mortality. Age- and sex-structured models have been used to express the dynamics of stock abundance, and the Beverton and Holt model has been used to express the relationship between stock and recruitment. Data for estimations are standardized catch per unit effort of commercial fishery for exploitable stock (1954–2006 and 1968–2008) and for glass eel (1954–2010, 1972–2004, and 1973–1997). From the results of the base case scenario of estimations, the estimated stock size of individuals aged ≥1 year was 18.7 thousand tons in 2010, which was 24 % of the carrying capacity. The estimated stock size has recovered since 1990. Maximum sustainable yield was 4,180 tons if only the exploitable stock were utilized, and 266 tons if only the glass eel were utilized. These results and issues relating to estimation and management for reducing the fishery impact on stock are discussed. 相似文献
9.
鄱阳湖刀鲚的渔汛特征及渔获物分析 总被引：2，自引：0，他引：2
通过探究鄱阳湖刀鲚(Coilia ectenes)的渔汛特征和渔获物现状,为有效地保护其种群资源提供科学依据。2013-2014年在鄱阳湖设置3个调查点,对刀鲚进行逐月采样调查,共取样986尾、41.54 kg,随机抽样调查不同捕捞网具的整船次鄱阳湖刀鲚渔获物数据,测量体长、体重等生物学参数。采用Pearson相关分析刀鲚单船日渔获重量WB与水文因子关系。结果表明,鄱阳湖刀鲚体长范围为17.9~38.1 cm,其中21.2~23.6 cm是优势体长组,占总个体数的37.02%;体重范围为14.3~198.2 g,其中25~40 g是优势体重组,占总个体数的57.20%。鄱阳湖刀鲚体长L(cm)和体重W(g)幂函数方程为:W=0.0019L3.1378(R2=0.8997;n=986;P0.01)。湖口水域刀鲚出现时间主要集中在每年的5-6月,高峰期在6月,7月很少见;单船渔获数量NB为(3.2±4.1)尾/d,单船渔获重量WB为(0.12±0.11)kg/d。湖口水域刀鲚单船渔获重量WB与该水域水位、流量均呈显著正相关(P0.05),WB与水位的相关性更为显著。与历史资料相比,鄱阳湖刀鲚渔获规格以小个体居多;渔汛稍有推迟,持续时间大幅度缩短;种群规模急剧缩小,表明刀鲚资源正在严重衰退。 相似文献
10.
为了解东莞生态园湿地水域群落结构特征,探讨2种类型刺网(沉网和浮网)及不同网目网片渔获物组成的差异性,实验利用多网目(1.0、1.25、1.6、2.0、2.5、3.1、3.9、4.8、5.8、7.0、8.6和11.0 cm)单层刺网对该湿地的鱼类进行了调查。研究期间共采集到13种鱼类,相对重要性指数显示,海南似和莫桑比克罗非鱼为优势种,前者密度最高(占84.8%),后者生物量居多(40.2%)。渔获物物种组成沉浮网间差异显著,但单位努力捕捞数量(NPUE)、单位努力捕获重量(BPUE)及物种数与沉浮网间均无显著差异;海南似的NPUE在2种类型刺网间无显著差异,但莫桑比克罗非鱼和尼罗罗非鱼的NPUE浮网显著低于沉网。12个网目网片的渔获物物种聚成2类,1.0～2.0 cm网目网片渔获物聚为1类,海南似为指示种;2.5～11.0 cm片的聚为另1类,莫桑比克罗非鱼和尼罗罗非鱼为指示种。渔获物大小结构聚为2类,1.0～3.9 cm网目网片渔获物聚为1类,4.8～11.0 cm网目网片的聚为另1类。随着网目大小增加,渔获物平均体长线性递增,NPUE呈幂函数式下降。研究表明,为对内陆水域鱼类群落... 相似文献
11.
Abstract. The catch from the fishery for the migratory Prochilodus platensis Holmberg on the Rio Pilcomayo shows considerable annual variation. Peaks were apparent in 1981 and 1982, followed by very low returns between 1983 and 1985 and a resurgence in 1986. The catch in 1986 was 1011t with the degree of annual variation probably lying between 500 and 2000t. In the Pilcomayo P. platensis is a rapidly growing short-lived fish with a maximum life expectancy of 6-7 years and an upper size approaching 61.5cm. The fish first migrate and appear in Bolivian' waters when they are 21/2-3 years old, having spent the first 2 years on the nursery grounds, probably on the Argentine/Paraguay section of the river. Although fish of this age were numerous in the 1986 catches, the optimal market size is rather larger, and older fish are taken preferentially. The fishery actually depends upon very few age classes. A comparison of growth and mortality rates obtained from scale reading and from length frequency analysis by ELEFAN programs showed a close agreement. The considerable fluctuations in the fishery are largely due to the highly variable flood regime of the river rather than to fishing pressure, with the flood determining recruitment in 2 years' time. Nevertheless, a combination of a sequence of poor flood years with sustained fishing pressure could seriously damage the fishery. 相似文献
12.
C. A. Gray D. D. Johnson D. J. Young & M. K. Broadhurst 《Fisheries Management and Ecology》2004,11(5):323-333
A scientific observer programme was used to quantify the composition and magnitude of discards in the gillnet fishery for dusky flathead, Platycephalus fuscus (Cuvier), in three barrier estuaries in New South Wales, Australia, during the 2001 fishing season. Regulations only permit the retention of legal‐sized dusky flathead and legal‐sized blue swimmer crab, Portunus pelagicus L., and mud crab, Scylla serrata (Forskål); all other organisms were discarded. Sampling was stratified into two time periods; before and after 1 July 2001 which coincided with the increase in the minimum legal length (MLL) of dusky flathead from 33 to 36 cm total length (TL). Eighty one catches were sampled, yielding 38 finfish species and two portunid crab species. Legal‐sized dusky flathead were the most abundant organism captured, accounting for 23–47% by number and 34–54% by weight of the mean observed catch depending on the estuary and survey period, with a mean catch of 25–59 flathead weighing 13–25 kg per fishing‐night. Species composition and relative abundance of catches differed among estuaries, but not between sampling periods. Predominant bycatch species included legal and undersize blue swimmer crab, sea mullet, Mugil cephalus L., luderick, Girella tricuspidata (Quoy & Gaimard), bream, Acanthopagrus australis (Günther) and yellowfin leatherjacket, Meuschenia trachylepis (Günther). These five species accounted for 82% of total bycatch by number and 71% by weight, pooled across the three estuaries. More crabs were retained than discarded, with retained legal‐size crabs (byproduct) accounting for 16% of total bycatch by number and 13% by weight, with an average of 5–22 crabs weighing 1–6 kg being caught per fishing‐night, depending on the estuary. Overall, 7% of dusky flathead captured (number) were below the MLL of 36 cm and discarded, suggesting the nets as currently configured may be relatively selective in catching legal‐size flathead. However, 41% of dusky flathead were <40 cm TL, indicating that if the MLL for this species is increased to this length as proposed, new nets must be introduced into the fishery. The findings are discussed in terms of making the flathead fishery more sustainable, including alternative management strategies for the fishery. 相似文献
13.
根据上世纪90年代及60年代的生物学资料，运用体长频率分析法估算二长棘鲷的生长和死亡参数。vonBertlanffy生长方程的主要参数L∞=27．3cm，K=0．45，t0=-O．34；体重的生长拐点为2．12龄；瞬时总死亡率(Z)、瞬时自然死亡率(M)和瞬时捕捞死亡率(F)分别为2.825，1．045和1．78。当前开发率为0．63，资源处于过度利用状态。根据等渔量曲线图分析，当前的捕捞强度过高，而开捕年龄和开捕体长过低，资源出现衰竭现象。综合考虑当前的捕捞强度和社会经济效益，建议北部湾二长棘鲷的最适开捕年龄大于1龄，开捕体长大于120mm。 相似文献
14.
There is international recognition for greater inclusion of recreational fisheries catch data in species, fisheries and ecosystem assessments. Recreational charter fisheries provide important social services and contribute to total species catches. This study compares and validates industry logbook catch and effort data (1,357 trips) against observer data (154 trips) across six ports in a recreational charter fishery in eastern Australia. The mean numbers of clients and fishing effort (hours) per trip varied inconsistently between data sources and among ports. Logbooks did not adequately report released catches, and the mean number of species retained per trip was consistently underestimated in logbooks compared to observer data. For both data sources, catch rates of total individuals and key species displayed similar trends across different units of effort; catch per hour, client, client/hour and trip. The mean catch rates of total individuals and most key species, except those retained for bait, were similar across data sources, as were estimates of total fleet harvests. The length compositions of retained catches of some key species displayed truncation of larger organisms in the observer data whereas other species did not. Despite the shortcomings of the logbook data, future fishery and species monitoring strategies could include industry and observer data sources. 相似文献
15.
P. A. A. T. Jayawardane D. S. Mclusky P. Tytler 《Fisheries Management and Ecology》2003,10(3):179-189
The population dynamics of Metapenaeus dobsoni (Miers) from the west coast of Sri Lanka was investigated based on catch/effort and length frequency data, using FiSAT software. Annual yield of M. dobsoni was estimated at 296 t in 1998 and 362 t in 1999. This species formed 54% of the total shrimp catch from the system. The asymptotic length (L) and the growth rate constant (K) were estimated to be 11.49 cm and 1.02 yr?1 for males and 12.8 cm and 1.73 yr?1 for females. The fishing mortality coefficients were 2.42 and 1.85 yr?1 for males and females, respectively. The natural mortality was estimated at 1.72 yr?1 for males and 2.51 yr?1 for females. The recruitment for the estuarine environment and the offshore areas was continuous but peaked twice per year. The maximum sustainable yield (MSY) was estimated at 294.65 t, around the current catch estimates. To obtain maximum sustainable economic yield (MSE = 293.56 t) the present effort should be reduced by 10%. 相似文献
16.
K.M. LEBER & S.M. ARCE 《Fisheries Management and Ecology》1996,3(3):261-278
Abstract This study showed that cultured striped mullet, Mugil cephalus L., released as juveniles can make a significant contribution to landings in an island commercial fishery. Following pilot hatchery releases from 1990 to 1993, striped mullet fisheries in Kaneohe Bay, Hawaii, USA, were sampled to recover cultured fish from the bay-wide catch. Direct sampling of 181 fishing trips resulted in recovery of 211 cultured striped mullet. By autumn 1994, cultured fish comprised 13.0% (2.8%) of the commercial mullet catch in Kaneohe Bay, and the percentage was increasing logarithmically. This study corroborated predictions from previous studies of juveniles about effects of release strategies on survival of cultured mullet. Following summer releases, recapture rates were strongly affected by fish size-at-release, with a critical release size of 60 mm total length (the smallest size released that was subsequently detected in the fishery). Over 30 000 juveniles stocked in 1990 (but not in a nursery habitat preferred by striped mullet) apparently suffered complete mortality. 相似文献
17.
为促进南海马鲛刺网渔业的可持续发展和渔业资源的合理利用,于2012年和2015年分别进行了马鲛流刺网渔获组成和选择性试验。运用相对重要性指数(IRI)评价刺网的渔获组成,并在SELECT模型(share each length catch total)的架构下,利用正态分布(Normal)和双峰分布(Bi-normal)概率方程计算刺网对康氏马鲛(Scomberomorus commersoni)的选择性;进一步结合康氏马鲛的最小可捕规格,探讨南海区马鲛流刺网的最小网目尺寸。结果表明,康氏马鲛是南海马鲛流刺网最重要的渔获种类,其2012年和2015年IRI值分别为9 472.00和14 363.02;调查试验共捕获康氏马鲛295尾,其中2012年康氏马鲛的众数叉长组为751~800 mm(占32.52%),2015年康氏马鲛的2个众数叉长组分别为501~550 mm和701~750 mm;正态分布模型估算的选择性众数相对叉长为6.961;双峰分布估算的2个众数相对叉长值分别为4.440和6.728;根据模型残差值的大小,认为双峰分布的拟合效果较好;将康氏马鲛可捕规格定为380 mm的前提下,建议南海马鲛流刺网的最小网目尺寸可暂定为120 mm。 相似文献
18.
达里湖东北雅罗鱼的生长、死亡和生活史类型的研究 总被引：2，自引：0，他引：2
达里湖东北雅罗鱼(Leucisus waleckii)的种群结构参数(体长、体重和年龄)进行测定,估算种群的生长和死亡参数,并研究种群的生活史类型。结果显示:东北雅罗鱼的体长和体重的关系式Wt=0.0281L2t.8152,其vonBertalanffy生长方程各参数为渐近体长L∞=28.9763 cm,渐近体重W∞=366.95 g,生长系数k=0.2586,t0=-0.3237;自然死亡系数M为0.322,总死亡系数Z为0.9386,捕捞死亡系数F为0.6166;生活类型为r-选择。结果表明:作为渔业管理对策,达里湖东北雅罗鱼的起捕年龄应定为3龄以上。 相似文献
19.
20.
Iwona Psuty-Lipska Niels Madsen Bohdan Draganik Wies&#x;aw Blady 《Fisheries Research》2006,80(2-3):339-344
This paper presents the scientific basis for changes in the minimum mesh size in gill nets, from 28 to 30 mm, introduced by fishery management in Poland to limit the catch of undersized perch (those less than 17 cm total length). Experimental fishing with six different mesh sizes was performed in accordance with commercial fisheries practice. A bi-normal selection curve was fitted to the data by including the between-set variation in the model. The locations of the primary and secondary modes of the bi-normal curve on the transformed length scale (length/mesh) were estimated to be 6.95 and 7.41, respectively. The results indicated that a minimum mesh size in gill nets of 28 mm should be sufficient to ensure a low level of discards as well as protecting the interests of fishermen. 相似文献