不同底质环境对眼斑猛虾蛄产卵孵化的影响

根据虾蛄自然生态特性,在室内小水泥池设计六种底质环境,试验不同底质、虾蛄自身挖掘与人造洞穴对眼斑猛虾蛄(Harpiosquilla annandalei)产卵与孵化的影响。结果表明:眼斑猛虾蛄的产卵与孵化对底质、洞穴等条件要求严格,没有合适的条件便不产卵,即使产卵也不孵化或孵化率很低,在几种底质条件中以泥沙底质最好,明显优于沙底质,水泥底质不孵化,泥沙底质是眼斑猛虾蛄产卵、孵化成功重要条件之一。虾蛄自身挖掘的洞穴优于人造洞穴,而对泥沙的比例也有一定要求,要有利于虾蛄筑成洞穴。     

春季黄河口海域2种网具渔获物组成的比较分析

根据2007年5月在黄河口海域弓子网和小型单船底拖网渔业资源调查资料,分析了2种网具的渔获物种类组成,并分别计算了Sorensen相似性指数（SS）、种类丰富度指数（R）、Shannon—Wiener多样性指数（H＇）、Pielou均匀度指数（J＇）和相对重要性指数（index of relative importance,IRI）。弓子网和底拖网的SS指数为0．63,2种网具渔获物组成的相似性较差。弓子网和底拖网的R、H’、J’指数分别为3．61、2．28、0．64和3．55、2．40、0．72,底拖网渔获物多样性程度高于弓子网。分析结果表明,2种网具的单位功率渔获量（catch per unit effort,CPUE）均不高,且存在选择性差和对幼体生物伤害严重的问题。     

New mitigation measures reducing seabird by‐catch in trawl fisheries

This paper provides an update on an earlier review [Fish & Fisheries 8 (2007) 31] of mitigation methods used to reduce seabird by‐catch in trawl fisheries. Interactions of seabirds with trawl vessels fall into two broad categories: those focused on the trawl warps and those focused around trawl nets. For reducing seabird strikes on trawl warps, the use of bird‐scaring lines has been proved to be the most effective mitigation device in the trawl fisheries in which comparative studies have been undertaken. However, the retention or strategic management of fish waste (offal and discards) is recommended as the most effective primary measure for by‐catch reduction, and as such should be viewed as the best long‐term solution to reducing seabird by‐catch in trawl fisheries. Coincident with effective fish waste management, measures such as cleaning the net prior to shooting and reducing the time the net is on the surface should be viewed as best practice measures and incorporated into normal fishing activities. While a number of methods have been trialled to reduce the incidence of warp strikes, there continues to be the need for more work on effective measures for reducing interactions of seabirds with the trawl net.     

胶州湾曼氏无针乌贼资源量与季节变化的调查研究

根据2005年和2006年逐月在胶州湾进行的底拖网调查,并对底拖网渔获物中的头足类进行定性定量分析与测定,利用扫海面积法评估胶州湾海域曼氏无针乌贼的资源量。调查分析了其分布特点与季节变化,并进行了渔获物中头足类组成的比较,分析了其种类组成、分布特点与季节变化特征。结果表明,胶州湾曼氏无针乌贼资源量有明显的季节变化,夏、秋两季的资源量明显高于其他季节,分别达到26.7t和21.5t（2006）;夏、秋两季的重量比明显高于其他季节,分别达到23.4%和27.8%。近几年,以曼氏无针乌贼为主捕对象的头足类资源量基本保持稳定,年平均资源量约14t,接近20世纪90年代中期的水平。     

黄河口鱼类底拖网调查采样断面数的优化

优化调查采样设计方案,利用有限的调查成本获取准确可靠的渔业资源数据,对于开展独立于渔业的科学调查十分重要。根据2013年8、10月和2014年2、5月在黄河口及其邻近水域进行的渔业资源底拖网调查数据,选取短吻红舌鳎(Cynoglossus joyneri)和矛尾虾虎鱼(Chaeturichthys stigmatias)作为目标鱼种,以其平均个体体长、平均个体体重为调查采样优化目标,利用计算机模拟方法对黄河口水域的渔业资源底拖网调查生物学数据进行再抽样,以平均体长、平均体重估计值的相对估计误差(REE)、相对偏差(RB)和变异系数(CV)作为优化评价指标,对基于整群抽样方法的黄河口及邻近海域的调查采样断面数进行优化。结果表明,对于目标鱼种的平均体长、平均体重指标,模拟估计值的REE、RB和CV均随着断面数的减少不断增加,调查断面数少于3时,各指标的变化幅度较大。断面数由5减少至3,REE值平均增加2%,RB值平均增加0.13%,CV值平均增加1.95%,同时渔获量降低近40%。因此,断面数为3可视为黄河口及邻近海域可接受的最优调查断面数。     

Effects of environmental variables on survey catch rates and distribution by size of shallow‐ and deep‐water Cape hakes,Merluccius capensis and Merluccius paradoxus off Namibia

In order to study the effects of temperature, oxygen, salinity and time of day on survey trawl catches, we modeled observed catches of juvenile, small, medium and large hakes per station as functions of zenith angle of the sun, geographical position, year, temperature, salinity, oxygen and depth. We used data from summer demersal surveys conducted during the period 2002–2015, together with a computation of the corresponding light level data from which the solar zenith angles were obtained, and fitted the generalized additive models to these data. Based on best model results, important covariates were oxygen, depth, geographical position and temperature. The best models explained 70%, 69%, 57% and 57% of the variability in catches of juvenile, small, medium and large Merluccius capensis, respectively, and 71%, 68%, 81% and 70% of juvenile, small, medium and large Merluccius paradoxus, respectively. The significant effects of temperature, oxygen, depth and geographical position on survey catches of hake of different size groups indicate that survey size structure may be affected by the behavior of both species towards environmental conditions. Greater care should therefore be taken when interpreting hake survey biomass estimates, based on swept area method, especially those that were collected during exceptional unfavourable environmental conditions. It would also be highly desirable if the oceanographic conditions are collected on each trawl station in order to improve understanding of the linkage between resources and environmental conditions.     

多囊桁拖网选择性研究中对照网囊网目尺寸的选择

对比作业法是拖网渔具选择性研究中重要的试验方法之一,而对比试验中对照网囊网目的选择至关重要。研究利用多囊桁拖网不同网目尺寸(20、30、35和40mm)网囊捕获的哈氏仿对虾、小黄鱼和棘头梅童鱼渔获体长分布数据,应用几何相似原理,分析过滤性渔具的选择性,并按不同假设条件下(假设1:符合几何相似原理对渔获具有一定的选择性;假设2:对渔获种类没有选择性),探讨如何合理选择对照网囊网目尺寸。结果表明,对照网网囊网目尺寸为20mm,在上述2种假设下,对选择性模型的拟合、简化及对其它网囊的选择性参数没有显著的影响;在考虑了桁拖网渔具各网囊具有相同相对作业强度,以及桁拖网渔具与普通拖网渔具选择性分析方法上的差异等因素后,认为在此项研究中,将小于20mm网目尺寸的网囊视为没有选择性的对照网囊是可行的。     

Habitat utilisation,growth and predation of Cucumaria frondosa: implications for an emerging sea cucumber fishery

Abstract Biological traits of the sea cucumber Cucumaria frondosa (Gunnerus) relevant to both ecological and management perspectives were investigated in the Newfoundland region. Abundance, size and fitness of adults were maximal on hard substrates. Larvae settled ～5 weeks post‐spawning and juveniles reached a maximum length of 6 mm after 24 months. Additional size classes of sea cucumbers kept under natural environmental conditions exhibited slow seasonal growth attuned to phytoplankton blooms, indicating that ～25 years may be required to reach market size. Juveniles of the predator sea star Solaster endeca (L.) readily fed upon 1.5‐2 mm long sea cucumbers. Predation rates on adult C. frondosa by adult S. endeca were modulated by temperature and biased towards injured specimens, suggesting that trawling may exacerbate predation pressure. The combination of slow growth and high predatory pressure enhanced by fishing activities emphasises the need for precautionary management of this emerging fishery in Atlantic Canada.     

Interannual-decadal variability of demersal fish assemblages in the Tsushima Warm Current region of the Japan Sea: Impacts of climate regime shifts and trawl fisheries with implications for ecosystem-based management

Data sets for two bottom trawl fisheries, the coastal pair-trawler fishery and offshore single-trawler fishery in the Tsushima Warm Current (TWC) region of the Japan Sea, were compiled and analyzed for the last three decades (1974-2006). These data sets were used to (1) identify and compare the variability in demersal fish assemblages, and (2) relate these to water temperature to examine the impacts of climate regime shifts. Principal component analysis (PCA) of catches of target species in the two trawler fisheries showed synchronous decadal variability with step changes around 1986/1987 and 1996/1997. These step changes strongly suggest the effect of the late 1980s climate regime shift, which was characterized by an abrupt change from a cool to a warm condition in the TWC. The first and second principal components (PC1 and PC2) for both trawler fisheries agreed closely with winter and summer water temperature in the Japan Sea, respectively, suggesting PC1 (PC2) was associated with cold- (warm-) water species. However, between warm- and cold-water species the response pattern to water temperature was different. CPUE (catch per unit effort) of warm- (cold-) water species correlated positively (negatively) with water temperature, indicating the increase in water temperature has a positive (negative) effect on warm- (cold-) water species. Cold-water species decreased (increased) both in biomass and distribution during the warm (cold) regime, while warm-water species increased in biomass and/or distribution during the warm 1990s. These results suggested that the demersal fish assemblage structure changed abruptly as a consequence of the late 1980s climate regime shift. Impact of fishing was unclear on the demersal fish assemblage as a whole, but fishing pressure has been intensified for specific species under unfavorable climate regimes even with a declining fishing effort. Differing response patterns between warm- and cold-water species to climate regime shifts suggest the importance of integrated assessment and ecosystem-based management for the whole trawl fishery rather than only for individual target species.     

Assessment of the ecological status of north‐eastern Adriatic coastal waters (Istria,Croatia) using macroalgal assemblages for the European Union Water Framework Directive

• 1. Based on the inclusion of macroalgae in the European Union Water Framework Directive as quality elements for the evaluation of the ecological status of coastal waters, the suitability of one (Ecological Evaluation Index, EEI) of several previously proposed evaluation methods in the particular ecological conditions of the northern Adriatic Sea was tested.
• 2. The EEI was assessed for 10 locations (polluted and putatively pristine) scattered along 60 km of the western Istrian coast. The sampling was performed seasonally at 1 and 3 m depth by destructive (determination of species cover and biomass) and non‐destructive (determination of species coverage using digital photography) methods.
• 3. When assessed at 1 m depth the spatial scale weighted EEI for the west Istrian coast was 8.1, corresponding to an ecological status class (ESC) value of high. However, data for 3 m depth gave a spatial EEI of 6.72 which corresponds to an ESC value of good. Regressions of the ratio of ecological state group I (ESG I, i.e. thick leathery, calcareous and crustose species) over total algal abundance with the pollution gradient (obtained using principal components analysis (PCA) ordination of environmental variables) were significant at 3 m but not at 1 m depth. This was due to the high abundance of ESG I macroalgae Corallina elongata and Cystoseira compressa at 1 m depth at polluted stations. Similar regressions were obtained using cover, biomass and coverage.
• 4. It is concluded that the EEI method may be suitable for the classification of coastal waters in the northern Adriatic only in certain cases. A better assessment of ecological status using this method would require more realistic estimations based on the inclusion of data from several sampling depths. As all three abundance measures (cover, biomass, coverage) gave similar results, coverage (using digital photography) is suggested as being a preferred measure owing to the rapidity of sampling at several depths and less time‐consuming laboratory work.

Copyright © 2008 John Wiley & Sons, Ltd.