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1.
为检测方目网囊对蓝圆鱼参和多齿蛇鲻的选择作用,2000年11～12月在南海北部海域试验了4种目大的方目网囊.结果表明,方形网目网囊有利于释放纺缍形(如蓝圆鱼参)、圆形或近圆形(如多齿蛇鲻)两种形体鱼类的小、幼鱼,且对后者的释放效果更好.当网囊目大分别为45、50 mm时,蓝圆鱼参的50%选择体长(L0.5)分别为121.22、128.77 mm;当网囊目大分别为40、45、50 mm时,多齿蛇鲻的L0.5分别为124.12、126.75、139.32 mm.通过不同目大网囊对蓝圆鱼参、多齿蛇鲻选择性比较分析,发现50 mm目大方目网囊的选择效果好于40、45 mm目大的网囊,因此,在南海区拖网渔业中采用50 mm目大的方目网囊是必要的,同时建议将150 mm作为蓝圆鱼参、多齿蛇鲻的最小可捕叉长标准. 相似文献
2.
为检测方目网囊对蓝圆Shen和多齿蛇鲻的选择作用，2000年11－12月在南海北部海域试验了4种目大的方目网囊。结果表明，方形网目网囊有利于释放纺缍形（如蓝圆Shen），圆形或近圆形（如多齿蛇鲻）两种形体鱼类的小，幼鱼，且对后者的释放效果更好。当网囊目大分别为45，50mm时，蓝圆Shen的50％选择体长（L0．5）分别为121.22,128.77mm；当网囊目大分别为40，45，50mm时，多齿蛇鲻的L0．5分别为124.12,126.75,139.32mm。通过不同目大网囊对蓝圆Shen，多齿蛇鲻选择性比较分析，发现50mm目大方目网囊的选择效果效果优于40，45mm目大的网囊，因此，在南海区拖网渔业中采用50mm目大的方目网囊是必要的，同时建议将150mm作为蓝圆Shen，多齿蛇鲻的最小可捕叉长标准。 相似文献
3.
为了科学地确定南海区拖网网囊的结构和适宜网目尺寸 ,于 2 0 0 0年 1 1月 2 5日～ 1 2月 2 0日在南海北部珠江口以外海域水深 36～ 70m拖网渔场 ,对 4种不同网目尺寸的方目网囊进行了网囊套网式捕鱼选择性试验 ,获得了蓝圆鱼参(Decapterusmaruadsi)、多齿蛇鲻 (Sauridatumbil)、条尾绯鲤 (Upeneusbensa si)等 3种主要鱼种的选择性曲线。试验结果表明 :4种方目网囊的数量平均逃逸率均高于重量平均逃逸率 ;网囊渔获的优势体长总是大于套网渔获的优势体长 ;蓝 鱼参、多齿蛇鲻、条尾绯鲤之类的圆体鱼类比扁体鱼类更易于逃出方目网囊。 相似文献
4.
南海区拖网方目网囊选择性试验 总被引：2，自引：0，他引：2
为了科学地确定南海区拖网网囊的结构和适宜网目尺寸，于2000年11月24日－12月20日在南海北部珠江口以外海域水深36－70m拖网渔场，对4种不同网目尺寸的方目网囊进行了网囊套网式捕鱼选择性试验，获得了蓝圆Cuan（Decapterus maruadsi)，多齿蛇鲻（Saurida tumbil)，条尾绯鲤（Upeneus bensasi)等3种主要鱼种的选择性曲线，试验结果表明，4种方目网囊的数量平均逃逸率均高于重量平均逃逸率，网囊渔获的优势体长总是大于套网渔获的优势体长，蓝Cuan，多齿蛇鲻，条尾绯鲤之类的圆体鱼类比扁体鱼类更易于逃出方目网囊。 相似文献
5.
将南海北部花斑蛇鲻分成南海北部大陆架和北部湾两个不同海域群体，计算花斑蛇鲻的生长与死亡参数。得到的Von Bertalanffy生长方程的相关参数为：南海北部大陆架L∞=45．5cm，K=0．28，t0=-0．460；北部湾L∞=40．0cm，K=0．30，t0=-0．443。计算自然死亡系数得南海北部大陆架为0．63；北部湾为0．67；捕捞死亡系数南海北部大陆架为0．79，北部湾为1．11。据等渔获量曲线建议南海北部大陆架花斑蛇鲻开捕体长由13．3cm增加至20．0cm，同时，捕捞死亡系数可由当前的0．79放宽至1．0；北部湾花斑蛇鲻开捕体长由13．5cm增加至19．0cm的同时，捕捞死亡系数可由当前的1．11放宽至1．5。 相似文献
6.
黄梓荣 《广东海洋大学学报》2002,22(6):26-31
根据实施休渔前 1997～ 1999年南海北部底拖网调查资料 ,以及实施休渔后 2 0 0 0～ 2 0 0 2年2 0 0nmile专属经济区渔业资源调查 (南海区 )最新资料 ,综合分析南海北部实施休渔前后多齿蛇鲻资源的变动趋势。结果表明 ,实施休渔后 ,海南岛以东和北部湾多齿蛇鲻渔获率分别提高了 5 7.75%和 84 .38% ,并呈现出自然的季节变化 ,渔获群体一龄鱼以下比例减少 ,一龄鱼以上比例增加。并讨论了资源养护的对策。 相似文献
7.
南海底拖网方、菱目网囊选择性研究 总被引：1，自引：0，他引：1
1997年 6月～ 1 998年 7月 ,使用 3种网目尺寸的方形网目网囊和一种网目尺寸的菱形网目网囊 ,在南海北部珠江口以外海域水深 3 5～ 96m拖网渔场进行了总共 2 6个有效网次的捕鱼对比试验 ,获得了关于蛇鲻、绯鲤、金线鱼 3种鱼种的选择性参数。结果表明 ,方形网目网囊比菱形网目网囊具有更好的选择性能 ,对于保护南海幼鱼资源是有效的 相似文献
8.
黄梓荣 《广东海洋大学学报》2003,23(1):41-44
采用 4 0 4 ◇/2 0 0mm底拖网 ,在南海北部进行进行 2 0 0nmile专属经济区渔业资源调查 ,测量其渔获 11种经济鱼类的体长数据 ,统计其没达到最小可捕规格所占比例。结果表明 ,渔获中未达到最小可捕规格的幼鱼比例很大 ,北部湾 ,带鱼、短尾大眼鲷和白姑鱼四季平均未达到最小可捕规格的幼鱼超过 30 % ;海南岛以东 ,花斑蛇鲻、带鱼、短尾大眼鲷、长尾大眼鲷和白姑鱼未达到最小可捕规格的幼鱼超过 30 %。同时提出了改进措施 ,即保留该网型 ,放大网目尺寸或将放大后的囊网网目改为方形网目 ;淘汰该网型 ,改囊网网目为方形网目、网目尺寸符合国家标准的四片式拖网网型。 相似文献
9.
南海北部花斑蛇鲻生长死亡参数估计及开捕规格 总被引：1，自引：0，他引：1
将南海北部花斑蛇鲻分成南海北部大陆架和北部湾两个不同海域群体 ,计算花斑蛇鲻的生长与死亡参数。得到的VonBertalanffy生长方程的相关参数为 :南海北部大陆架L∞ =4 5.5cm ,K =0 .2 8,t0 =- 0 .4 6 0 ;北部湾L∞ =4 0 .0cm ,K =0 .30 ,t0 =- 0 .4 43。计算自然死亡系数得南海北部大陆架为 0 .6 3;北部湾为 0 .6 7;捕捞死亡系数南海北部大陆架为 0 .79,北部湾为 1.11。据等渔获量曲线建议南海北部大陆架花斑蛇鲻开捕体长由 13.3cm增加至 2 0 .0cm ,同时 ,捕捞死亡系数可由当前的 0 .79放宽至 1.0 ;北部湾花斑蛇鲻开捕体长由 13.5cm增加至 19.0cm的同时 ,捕捞死亡系数可由当前的 1.11放宽至 1.5。 相似文献
10.
黄梓荣 《广东海洋大学学报》2003,23(1):41-44
采用404^◇／200mm底拖网，在南海北部进行进行200n mile专属经济区渔业资源调查，油量其渔获11种经济鱼类的体长数据，统计其没达到最小可捕规格所占比例。结果表明，渔获中末达到最小可捕规格的幼鱼比例很大，北部湾，带鱼、短尾大眼鲷和白姑鱼四季平均末达到最小可捕规格的幼鱼超过30％；海南岛以东，花斑蛇鲻、带鱼、短尾大眼鲷、长尾大眼鲷和白姑鱼未达到最小可捕规格的幼鱼超过30％。同时提出了改进措施，即保留该网型，放大网目尺寸或将放大后的囊网网目改为方形网目；淘汰该网型，改囊网网目为方形网目、网目尺寸符合国家标准的四片式拖网网型。 相似文献
11.
Population parameters and dynamic pool models of commercial fishes in the Beibu Gulf, northern South China Sea 总被引：3，自引：0，他引：3
Length-frequency data of eight commercial fish species in the Beibu Gulf (Golf of Tonkin), northern South China Sea, were collected during 2006-2007. Length-weight relationships and growth and mortality parameters were analyzed using FiSAT II software. Five species had isometric growth, two species had negative allometric growth, and one species had positive allometric growth. Overall, the exploitation rates of the eight species were lower in 2006-2007 than in 1997-1999: for four species (Saurida tumbil, Saurida undosquamis, Argyrosomus macrocephalus, and Nemipterus virgatus) it was lower in 2006-2007 than in 1997-1999, for two species (Parargyrops edita and Trichiurus haumela) it remained the same, and for the other two species (Trachurus japonicus and Decapterus maruadsi) it was higher in 2006-2007 than in 1997-1999. The exploitation rates might have declined because of the decline in fishing intensity caused by high crude oil prices. The optimum exploitation rate, estimated using Beverton-Holt dynamic pool models, indicated that although fishes in the Beibu Gulf could sustain high exploitation rates, the under-size fishes at first capture resulted in low yields. To increase the yield per recruitment, it is more effective to increase the size at first capture than to control fishing effort. 相似文献
12.
Comparative fishing experiments were carried out in 2010 using tube traps with five hole diameters (8, 15, 18, 20 and 22 mm) to establish the size selectivity of escape holes for white-spotted conger. Selectivity and split parameters of the SELECT model were calculated using the estimated-split and equal-spilt model. From likelihood ratio tests and AIC (Akaike’s Information Criterion) values, the estimated-split model was selected as the best-fit model. Size selectivity of escape holes in the tube traps was expressed as a logistic curve, similar to mesh selectivity. The 50% selection length of white-spotted conger in the estimated-split model was 28.26, 33.35, 39.31 and 47.30 cm for escape-hole diameters of 15, 18, 20 and 22 mm, respectively. The optimum escape-hole size is discussed with respect to management of the white-spotted conger fishery. The results indicate that tube traps with escape holes of 18 mm in diameter would benefit this fishery. 相似文献
13.
Trawl is a main fishing gear in Chinese fishery,capturing large fish and letting small ones at large.However,long-term use of trawl would result in changes of phenotypic traits of the fish stocks,such as smaller size-at-age and earlier age-at-maturation.In this study,we simulated a fish population with size characteristics of trawl fishing and the population produces one generation of offspring and lives for one year,used trawl to exploit the simulated fish population,and captured individuals by body size.We evaluated the impact of the changes on selectivity parameters,such as selective range and the length at 50% retention.Under fishing pressure,we specified the selectivity parameters,and determined that smaller selection rates and greater length at 50% retention were associated with an increased tendency towards miniaturization. 相似文献
14.
尿素包合法富集蛇鲻鱼油中EPA和DHA的研究 总被引：2，自引：0，他引：2
以蛇鲻精制鱼油为原料,采用氢氧化钾乙醇皂化和硫酸酸化制备鱼油混合脂肪酸,以EPA和DHA含量为指标,探讨了尿素包合法富集鱼油中EPA和DHA的工艺条件。结果表明:以乙醇为溶剂,在尿脂质量比为2︰1和包合温度0℃的条件下进行一次性包合20 h后,富集产物中EPA和DHA总含量达到了69.74%,其中EPA含量为22.05%,DHA含量为47.69%,达到了保健鱼油的生产要求。 相似文献
15.
In order to determine the effect of twine thickness on the size-selectivity of the driftnet used for the yellow croaker, size-selectivity tests were conducted with three different twine thicknesses (monofilament diameters of 0.279 mm (number’s method; No. 3), 0.321 mm (No. 4), and 0.360 mm (No. 5)) of driftnets for the yellow croaker in the seas around Chooja-do, Jeju Islands. The selectivity curve was estimated by using Kitahara’s method. In order to determine the physical properties of the twine used in the experimental fishing nets, we measured the breaking load, elongation, and stiffness under both dry and wet conditions. In terms of physical properties, the thinnest twine (No. 3) had the strongest breaking strength per unit cross-sectional area, along with good elongation and excellent flexibility. The thickest twine (No. 5) had the lowest flexibility. In terms of selectivity, the net of No. 3 twine showed the broadest selection range and, thus, a relatively low selectivity compared with the other nets, while the less flexible net of No. 5 twine showed the narrowest selectivity range and high selectivity. In addition, it was found that a thicker twine resulted in a smaller haul of small fish. Therefore, it can be inferred that the thickness of the twine affects the size of the catch and selectivity, and thus the size composition of the catch as well. 相似文献
16.
不同结构网囊特性的初步研究 总被引：1，自引：0，他引：1
杨吝 《广东海洋大学学报》1998,(2)
为了测定不同拖网网囊结构对网囊的几何形状、同目张开、网目形状和拖网阻力的影响,设计和制作了4种网囊,一种是传统的菱形同目（DM）网囊,另三种是新型网囊：方形同目（SM）网囊,菱、方形网目混合二片式（DSM2）网囊和菱、方形同目混合四片式（DSM4）网囊。于1996年9月11～12日在中山大学试验水槽进行了同模试验,结果表明：1）各网囊阻力相差不大,且随拖速和渔获的增加而增大。2）新型网囊的几何形状和同目的张开及其形状均优于传统菱形网目网囊。3）空网时,各种网囊均呈圆筒状。当网囊中有了渔获后,传统菱形同目网囊的端部变为球状,除了球状部分的网目有较大张开外,其余同目张开很小,网囊使用直径也小,而新型网囊始终保持筒状,且网目充分张开,网囊使用直径也大。4）新型例翼的几何形状及使用直径和网目的张开及形状几乎不受拖速大小、有无渔获和渔获多少的影响。 相似文献
17.
《中国海洋湖沼学报》2016,(6)
In order to determine the effect of twine thickness on the size-selectivity of the driftnet used for the yellow croaker, size-selectivity tests were conducted with three different twine thicknesses(monofi lament diameters of 0.279 mm(number's method; No. 3), 0.321 mm(No. 4), and 0.360 mm(No. 5)) of driftnets for the yellow croaker in the seas around Chooja-do, Jeju Islands. The selectivity curve was estimated by using Kitahara's method. In order to determine the physical properties of the twine used in the experimental fi shing nets, we measured the breaking load, elongation, and stiffness under both dry and wet conditions. In terms of physical properties, the thinnest twine(No. 3) had the strongest breaking strength per unit cross-sectional area, along with good elongation and excellent fl exibility. The thickest twine(No. 5) had the lowest fl exibility. In terms of selectivity, the net of No. 3 twine showed the broadest selection range and, thus, a relatively low selectivity compared with the other nets, while the less fl exible net of No. 5 twine showed the narrowest selectivity range and high selectivity. In addition, it was found that a thicker twine resulted in a smaller haul of small fi sh. Therefore, it can be inferred that the thickness of the twine affects the size of the catch and selectivity, and thus the size composition of the catch as well. 相似文献
18.
Based on two bottom trawl surveys conducted in autumn 2000 and 2001, a total of 1106 stomach samples of Bombay duck Harpadon nehereus between 23–278 mm fork length were collected and analyzed. The results show that Bombay duck prey items consisted of 11 groups or 32 species, of which Apogon lineatus, Leptochela gracilis, Acetes chinensis, and Euphausia pacifi ca were the dominant prey species. Ontogenetic variations were found in feeding habits and feeding activity of Bombay duck. Feeding activity was highest in fi sh smaller than 50 mm, lowest in fi sh between 50 and 99 mm, and then increased with increasing size thereafter. As Bombay duck size increased, fi sh prey increased in importance, whereas euphausiids and decapods decreased in importance. Different trophic guilds were observed in feeding habits across the examined size range. Bombay duck smaller than 50 mm were zooplanktivores, mainly feeding on zooplankton and fi sh larva; those between 50 and 149 mm were generalist predators, mainly feeding on pelagic shrimps, demersal shrimps and fi shes; and those larger than 150 mm were piscivores, mainly feeding on fi shes. 相似文献
19.
《中国海洋湖沼学报》2017,(6)
The reproductive biology of bream A bramis brama(L.) was studied from 546 fish collected from the lower reaches of the Irtysh River in Xinjiang, north-west China, from March to November 2013. The overall sex ratio(M/F) was 1.06:1, and was not significantly diff erent from the theoretical 1:1 ratio( P 0.5). However, there was a dominance of males during the pre-spawning season(1.33 in March and 1.56 in April, P 0.5), while females were dominant during the peak spawning season(0.88 in June, P 0.5). The monthly variation in gonadosomatic index(GSI) and proportion of gonads at each macroscopic maturity stage, indicated that A. brama spawned once a year with peak spawning occurring from late May to June. The unimodal distribution of oocyte diameter each month indicated that A. brama is a single spawner, with a high degree of spawning synchronicity. The standard lengths(SL 50) and ages( A 50) at first maturity for males and females, were 178 and 204 mm, and 5.6 and 6.8 years, respectively. The mean absolute fecundity(AF) was 77 311 eggs per fish, and mean relative fecundity(RF) was 162 eggs per gram of body weight(BW). The AF of A. brama increased linearly with increasing of gonad weight(GW), eviscerated weight(EW) and standard length(SL), but was not significantly correlated with age. As, A. brama in the lower reaches of the Irtysh River reaches reproductive maturity relatively late in their life span, is mature for a short period and spawns in aggregations, this fish is vulnerable to overexploitation. 相似文献
20.
观察了珠江斑鳠3批次受精卵的胚胎发育,描述及记录了胚胎发育各期的形态特征及所需时间。斑鳠的成熟卵子呈圆形,黄色,卵子直径为3.1~3.8 mm,吸水后最大卵径为4.0~4.2 mm,受精卵黏性很小。珠江斑鳠胚胎发育与其他硬骨鱼类基本相似,属于盘状卵裂。在水温(27.5±0.5)℃时,受精后约1 h 10 min进入胚盘形成期,受精2 h 15 min后进入卵裂期,受精后7 h 50 min,进入囊胚期,再经约13 h 45 min进入原肠期,受精后21 h15 min,胚孔封闭,当受精39 h 5 min后,心脏开始出现搏动,受精后55 h,仔鱼开始孵出。 相似文献