梁子湖乌鳢种群动态及最大持续渔获量的研究

根据1997年3月—1998年2月在梁子湖取得的672尾乌鳢标本研究了其种群动态及最大持续渔获量。用鳞片鉴定年龄,鳞径与体长的关系为L=2.7683 9.0184S;体长与体重的关系为W=0.0126L~(3.0197),体长与体重的von Bertalanffy生长方程为:L_t=81.03×[1-e~(-0.1755(t 0.5690))];W_t=7310×[1-e~(-0.1755(t 0.5690))]~(3.0197)。种群的年总死亡率为0.5232,自然死亡率为0.3049,捕捞死亡率为0.2182。通过比较各种捕捞强度和最小捕捞规格的不同的总渔获量和群体的相对数量,提出获得持续渔获量的捕捞强度F=0.40和最小捕捞年龄t_c=4。     

长吻[Leiocassis longirostris (Günther)]的种群生态学及其最大持续渔获量的研究

本文研究长江中下游长吻的种群生态学特性并进行渔业生物学分析。胸鳍棘、尾舌骨及脊椎骨都可用作年龄鉴定材料。用Brody-Bertallanffy的公式表述体长、体重与年龄的关系。调查生殖特性并分析比较产卵力及产卵群体的结构类型。以食物出现率和重量法评价各类食物在食料中的作用。由渔获物统计资料计算种群的自然死亡率和捕捞死亡率。通过比较各种捕捞强度和最小捕捞规格的不同的总渔获量和繁殖群体的相对数量,提出获得最大持续渔获量的捕捞强度和最小捕捞规格。     

长吻鮠[Leiocassis longirostris（Giinther）]的种群生态学及其最大持续渔获量的研究

本文研究长江中下游长吻鲍的种群生态学特性并进行渔业生物学分析。胸鳍棘、尾舌骨及脊椎骨都可用作年龄鉴定材料。用Brody—Bertallanffy的公式表述体长、体重与年龄的关系。调查生殖特性并分析比较产卵力及产卵群体的结构类型。以食物出现率和重量法评价各类食物在食料中的作用。由渔获物统计资料计算种群的自然死亡率和捕捞死亡率。通过比较各种捕捞强度和最小捕捞规格的不同的总渔获量和繁殖群体的相对数量,提出获得最大持续渔获量的捕捞强度和最小捕捞规格。     

闽南—台湾浅滩渔场羽鳃鲐生长和死亡的研究

本文报道闽南—台湾浅滩渔场羽鳃鲐的生长特性和死亡参数,并讨论了捕捞规格问题。其纯体重 W 和总体重 W’与叉长的相关式分别为 W=2.5687×10~(-7)L~(3.7545),W’=1.003×10~(-6)L~(3.5140);叉长生长方程 L_t=346.5[1-e~(-0.2209(t+1.2263))]~(0.5700),体重生长方程 W_t=881.1[1-e~(-0.2209(t+1.2263))]~(2.1399);1988—1989年种群存活率为0.2808,瞬时总死亡率为1.2600,瞬时自然死亡率和瞬时捕捞死亡率分别为0.5863和0.6738;最佳最小捕捞叉长为170.3mm,最佳最小捕捞纯体重和总体重分别为63.9g 和71.0g.     

尖头塘鳢(Eleotris oxycephala Temmiuck et Schlegel)的年龄、生长和生活史类型的研究

本文采用胸鳍第二支鳍骨为研究东江尖头塘鳢的年龄鉴定材料。胸鳍第二支鳍骨(远侧部)长的骨(R)与体长(L)的关系L=10.6565 54.3848R。用von Bertalanffy生长方程可表达体长、体重与年龄的关系:L=298.6(1-e~(-0.2313(t 0.3028))];W_t=577.4(1-e~(-0.2313(t 0.3028))]~3。根据r-选择和K-选择的典型特征以及渐近体长(L_∞)、渐近体重(W_∞)、生长系数(K)、瞬时自然死亡率(M)、初次生殖年龄(T_m)、最大年龄(T_(max))和性腺指数(GI)等7个生态学参数值,可以判断尖头塘鳢偏向r-选择。应用平衡产量模式计算改变瞬时捕捞死亡率(F)和渔业补充年龄(t_c)时的产量变化,同样证实尖头塘鳢生活史偏向r-选择。作为渔业管理对策,尖头塘鳢的捕捞年龄可定为2—3龄,以2龄为主,这样既能保护资源,又能获得较好的经济效益。     

东江七种鱼类的生活史类型研究

本文通过渐近体长(L∞)、渐近体重(W∞)、生长系数(K)、初次生殖年龄(Tm)、最大年龄(Tmax)、瞬时自然死亡率(M)和性腺指数(Gl)等7个生态学参数来分析鱼类种群生活史类型。根据r-选择和K-选择的典型特征以及各参数间相互关系的显著性,性腺指数、瞬时死亡率和生长系数是判断东江7种鱼类种群偏向rF)和改变渔业补充年龄(tc)时的产量变化,分析产量变化曲线可知,作为偏向r型的种群,提高捕捞强度不能增加渔业产量,适当的捕捞强度可以取得较高的产量;在低龄阶段提高起捕年龄能增加一定产量,但到达一定年龄后再提高起捕年龄,反而引起产量大幅度下降。只有合理控制捕捞强度和起捕年龄,才能获取最大持续产量。       

基于单位补充量模型的西江广东鲂种群资源利用现状评价

广东鲂(Megalobrama terminalis)是珠江中下游最重要的经济鱼类之一, 但由于过度捕捞和栖息地破坏, 资源日趋衰退, 科学评估其资源利用现状, 对合理开发与科学养护具有重要意义。利用2009—2015年西江肇庆江段渔业资源调查监测数据, 分析了广东鲂生长与死亡相关特征及参数变化; 利用单位补充量渔获量(Yield per recruitment, YPR)模型、单位补充量产卵群体生物量(Spawning biomass per recruitment, SBR)和生物学参考点评估了西江肇庆江段广东鲂资源利用状况。结果表明: 西江广东鲂体长(L)和体重(W)关系为W=1.518×10–5L3.051(R2=0.962, n=2252), 生长方程为L_t=419.989[1–e–0.225(t+0.172)]; 现有捕捞强度(F平均1.27/年)远超过种群开发可承受水平(F_40%=0.53, F_0.1=0.27, F_20%=0.94); YPR_ave=30.58 g, 远低于YPR_0.1(36.73 g)和YPR_max(45.89 g); SBR=11.5%, 低于20%的下限临界参考点。西江广东鲂种群资源已过度开发, 处于补充型捕捞过度和生长型捕捞过度状态。目前珠江禁渔期制度的实施对广东鲂资源补充起到了良好作用, 但提高开捕体长至250 mm资源恢复效果将更明显。     

长江中、上游铜鱼的生长特性

铜鱼是长江中上游的重要经济鱼类和天然捕捞对象,1990—1995年作者利用在长江中上游收集的1030尾标本,对铜鱼的生长特性进行了研究。其体重和体长的关系为W=0.005413L~(3.113)(r=0.9982),生长方程为L_t=60.0229[1-e~(-0.2325(t 0.6108))];W_t=3261.9137[1-e~(-0.2325(t 0.6108))]~(3.113),体重生长拐点t=4.2龄,相应的体长41.05cm、体重973.03g。按生长指标值分析,阶段生长可明显地划分为两个时期,即4龄前的生长迅速期和4龄后的生长减缓期。因此,天然渔业的捕捞规格应控制在约1000g以上的个体,目前在葛洲坝以下的中游江段主要捕捞幼鱼的现状应该改变。     

长江上游龙溪河厚颌鲂种群资源的利用现状和保护

由于栖息地被破坏和过度捕捞等人为因素的影响,长江上游特有鱼类厚颌鲂Megalobrama pellegrini的种群资源显著减少.利用单位补充量模型进行分析,结果显示:长江上游支流龙溪河的厚颌鲂种群资源已经被过度开发,现有的捕捞强度(0.94年-1)远超过种群可承受的水平(F40%=0.18年-1,F0.1=0.20年-1和F25%=0.30年-1);繁殖潜力比为4.50%,低于25%,将造成种群的补充量不足,导致种群资源量下降;限制捕捞强度和捕捞规格是控制过度捕捞、保护种群资源的有效措施.     

色林错渔业生产的现状与可持续利用的对策

色林错裸鲤（Gymnocypris selincuoensis)是藏北色林错湖泊中惟一的一种鱼类。本文介绍了色林错渔业的开发利用情况,并对色林错裸鲤最小捕捞年龄、捕捞强度、最小网目以及最佳年捕捞产量进行了探讨。从可持续发展的角度,我们认为对色林错鱼类资源的利用必须以保证现有湖泊生态系统的稳定为核心,在满足维持一个足够数量及年龄结构的繁殖群体的基础上,以获得最佳持续经济利益为目标。以往强调甚至采用的最大持续产量理论在高原极端环境条件下并不能作为鱼类资源利用的追求目标或确定渔产量的标准,而只能作为对其捕捞强度的参考。总的允许渔获量应当根据最适捕捞死亡率F0．2来确定。本文最后提出了色林错湖泊鱼类资源可持续利用的8条具体措施。     

急性病毒性肝炎的发病率慢性肝炎患病率和肝病死亡率的研究

1984～1987年,在黑龙江、河北、河南、湖南、上海五个省市城乡10.08855人口中进行急性肝炎发病率、慢性肝炎患病率、与病毒性肝炎有关的肝病死亡率的研究。急性肝炎标化发病率为152.19/10万,主要发生在20～50岁组人群;因无甲肝暴发流行,除上海外各点季节发病率分布均衡。慢性肝炎标化患病率为158.25/10万(诊断标准为6个月前有明确急性肝炎病史,现有明显的临床症状或体征,肝功能异常,故实际慢肝患病率要高于此数字);与病毒性肝炎有关的肝病死亡(包括肝癌)标化率为22.65/10万,其中肝病为 13.14/10万。男性死亡率显著高于女性。     

THE ROLE OF PREDATION IN THE ECOLOGY OF THE RINGED SEAL IN BARROW STRAIT, NORTHWEST TERRITORIES, CANADA

Predation on ringed seals ( Phoca hispida ) was examined in Barrow Strait between March and May 1984 to 1986. Polar bears were the most important predator. Evidence of bear predation was observed at 18–30% of the ringed seal subnivean structures we located. Ten to 24% of predation attempts were successful, with pups making up 75% to 100% of the seals killed. Bears killed an average of 0.08 to 0.51 seals/km², which comprised 8 to 44% of the estimated annual pup production. Bears were successful on average in 11.3% of their attempts to kill pups hidden inside birth lairs. On southeast Baffin Island where snow was soft and pups were exposed, bears were successful in 33.5% of their attempts to kill a seal. Negative correlations were found between mean snow depth and predation by polar bears ( r = -0.896, P = 0.04, n = 5) in 1985, and between snow depth and the number of predation attempts ( r = -0.613, P = 0.02, n = 14) in 1986.     

THE ECOLOGY OF SEXUAL CONFLICT: BACKGROUND MORTALITY CAN MODULATE THE EFFECTS OF MALE MANIPULATION ON FEMALE FITNESS

Sexual and parental conflicts can arise because males benefit by inducing elevated reproductive effort in their mates. For females, the costs of such manipulation are often manifested later in life, and may therefore covary with female life expectancy. Here, I outline a simple female life‐history model where female life expectancy reflects extrinsic mortality rate, and elevated reproductive effort causes accelerated senescence. Using this model, I show that variation in extrinsic mortality rate can modulate the magnitude and sign of fitness effects that male manipulation has on females. This result has several interesting implications. First, it suggests that the fitness effects of sexual interactions can depend on ecological factors, such as predation, that influence life expectancy. Second, if mortality risk is condition‐dependent but reproductive effort is not fully optimized in relation to individual condition, then sexual conflict intensity may increase with individual condition, selecting for condition‐dependent reproductive strategies. Third, if males vary in manipulativeness, then the fitness effects of mating with a given male phenotype may depend on both female condition and extrinsic mortality rate. Fourth, life span extension in the laboratory can lead to overestimation of sexual and parental conflicts. Life expectancy may therefore be a key factor in sexual coevolution.     

CALCULATING LIMITS TO THE ALLOWABLE HUMAN-CAUSED MORTALITY OF CETACEANS AND PINNIPEDS

A simulation method was developed for identifying populations with levels of human-caused mortality that could lead to depletion, taking into account the uncertainty of available information. A mortality limit (termed the Potential Biological Removal, PBR , under the U. S. Marine Mammal Protection Act) was calculated as the product of a minimum population estimate ( N _MIN), one-half of the maximum net productivity rate ( R _MAX), and a recovery factor ( F _R). Mortality limits were evaluated based on whether at least 95% of the simulated populations met two criteria: (1) that populations starting at the maximum net productivity level ( MNPL ) stayed there or above after 20 yr, and (2) that populations starting at 30% of carrying-capacity ( K ) recovered to at least MNPL after 100 yr. Simulations of populations that experienced mortality equal to the PBR indicated that using approximately the 20th percentile (the lower 60% log-normal confidence limit) of the abundance estimate for N _MIN met the criteria for both cetaceans (assuming R _MAX= 0.04) and pinnipeds (assuming R _MAX= 0.12). Additional simulations that included plausible levels of bias in the available information indicated that using a value of 0.5 for F _R would meet both criteria during these "bias trials." It is concluded that any marine mammal population with an estimate of human-caused mortality that is greater than its PBR has a level of mortality that could lead to the depletion of the population. The simulation methods were also used to show how mortality limits could be calculated to meet conservation goals other than the U. S. goal of maintaining populations above MNPL .     

PRODUCTION OF THE AFRICAN CATFISH (CLARIAS GARIEPINUS) I. GROWTH,MORTALITY AND YIELD SOUTH OF THE ZAMBEZI

SUMMARY

Clarias gariepinus were sampled from eight water bodies in southern Africa between 1973 and 1975. Aging results indicate a similar growth pattern for most areas with a near linear age-length relationship. Between year growth compensation was found to be present in Lakes Kyle and Mcllwaine in Zimbabwe, and to a lesser extent in Hardap Dam, South West Africa, but not present in Lake Kariba, Zimbabwe.

The fishable biomass of catfish from Lake Kyle is estimated between 0,61 to 1,14 kg ha^?1. Fishable biomass for all species is in the range 12,1 to 22,7 kg ha^?1.

The instantaneous growth rate was found to be between 0,20 and 0,25 for fully recruited age groups. The fishing mortality appears to be in the range of 0,4 for Lakes Kyle and Kariba and 0,5 for Lake McIlwaine. All of these levels are above the yield per recruit F₀, 1 levels of 0,27, 0,28 and 0,24 respectively which would normally indicate that each of these stocks is being overexploited. However, this does not appear to be the case in these tropical impoundments.     

WATER TEMPERATURE AND THE 1987 FISH KILL AT LAKE ST LUCIA ON THE SOUTH EASTERN COAST OF AFRICA

Summary

An unusually cold spell during the winter of 1987 caused a drop in water temperature at Lake St Lucia. This coupled with typical estuarine salinities in the lake resulted in a fish kill. The kill was one of the largest recorded in a South African estuarine environment and involved an estimated 250,000 fish comprising at least 21 species. Most fish that died belonged to small species. Densities of dead fish recorded along the lake's shoreline ranged from 0.1 to 16.6 fish per metre. It is concluded that the combination of low water temperature and near marine salinities was the major cause of the 1987 fish kill at Lake St Lucia.     

安徽虫瘟霉对桃蚜的生物测定与时间-剂量效应分析

用“孢子浴”法将人工培养的安徽虫瘟霉（Ｚｏｐｈｔｈｏｒａａｎｈｕｉｅｎｓｉｓ）对桃蚜（Ｍｙｚｕｓｐｅｒｓｉ ｃａｅ）接种而进行定量生物测定（１８℃,光周期为Ｌ∶Ｄ１２∶１２）,包括１０个剂量（１．５～１９７．７个分生孢子／ｍｍ２）,每剂量处理蚜虫６４～１２０头,逐日观察记载死亡数至第７ｄ。接种后第３ｄ在高剂量处理中始见少量死蚜,第４～６ｄ为死蚜盛期。所获数据很好地拟合时间 剂量 死亡率模型,由模型参数估计出该菌作用于桃蚜的时间效应随剂量增大而减小,在３７．１～１９７．７个分生孢子／ｍｍ２的剂量范围内ＬＴ５０值为４．５～６．７ｄ;剂量效应在接种后随时间递减,第５～７ｄ的ＬＤ５０分别为８６．８、４３．７和３４．１个分生孢子／ｍｍ２。结果表明,安徽虫瘟霉是一种较为理想的杀蚜微生物,在寄主体内的潜伏期为４～５ｄ。     

REPRODUCTIVE SYNCHRONY AND THE ESTIMATION OF MEAN DATE OF BIRTH FROM DAILY COUNTS OF NORTHERN FUR SEAL PUPS

Two methods for estimating the mean date of birth from daily counts of northern fur seal pups ( Callorhinus ursinus ) are presented and applied to data collected on the Pribilof Islands in 1951, 1962, 1963 and 1983. The mean date of birth over the four years was July 9. Reproduction is highly synchronized and consistent from one year to the next. Pupping occurs over a five week period with over 50% of the pups being born during the first two weeks of July.     

EXTREME SELECTION ON SIZE IN THE EARLY LIVES OF FISH

Although fitness typically increases with body size and selection gradients on size are generally positive, much of this information comes from terrestrial taxa. In the early life history of fish, there is evidence of selection both for and against larger size, leaving open the question of whether the general pattern for terrestrial taxa is valid for fish. We reviewed studies of size‐dependent survival in the early life history of fish and obtained estimates of standardized selection differentials from 40 studies. We found that 77% of estimated selection differentials favored larger size and that the strength of selection was more than five times that seen in terrestrial taxa. Selection decreased with study period duration and initial length, and disruptive selection occurred significantly more frequently than stabilizing selection. Contrary to expectations from Bergmann's rule, selection on size did not increase with latitude.