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。     

Value-added sampling for fishery independent surveys: Don’t stop after you’re done counting and measuring

Most fishery independent surveys count, weigh, and measure the majority of species caught. Many surveys also collect selected body structures for in-lab age determinations for selected species. We provide examples from the Northeast Fisheries Science Center's (NEFSC) bottom trawl survey that detail the development of at-sea sampling to elucidate age, growth, maturity, fecundity, spawning season, stomach contents, diet composition, condition, habitat types and prey preferences, basic oceanography (or limnology), and bioenergetics for a suite of diverse species. We show how the development of new methodologies and technologies has decreased both deck-time and time in the lab for processing many of the samples required to provide information on the topics listed above. As new technologies develop to make our trawl catch processing more efficient, we assert that we can notably increase the amount of information collected from trawl surveys with little additional effort. We show that with marginally additional catch processing time on the deck, at-sea sampling can provide a significant return on the knowledge of aquatic and marine resource species, non-resource species, habitats, food webs, and the ecosystems within which they occur. As observing systems continue to expand their remit to provide ecosystem management advice, the need for increased efficiencies on fisheries surveys will remain.     

Proximity of Pacific cod to the sea floor: Using archival tags to estimate fish availability to research bottom trawls

The percentage of Pacific cod available to Alaskan bottom trawl surveys was estimated from the proximity of tagged cod to the seafloor. Archival tags recorded time and depth data at 15- or 30-min intervals. The distance of a cod above the bottom was computed by subtracting tag depth from bottom depth, estimated as the maximum depth recorded during each 24-h day. These estimates of bottom depth are based on the assumption that cod approach the seafloor at least once a day, and do not undergo migrations up or down bottom gradients. To ensure that migrations over variable bottom gradients did not confound our estimates of bottom depth, we narrowed our analysis to 11 tagged cod that were recaptured in areas of flat bathymetry, and only analyzed data recorded within one month prior to recapture (N = 29,462 depth recordings). Pacific cod maintained short distances above the seafloor that often differed between day and night. Over 95% of the daytime tag recordings occurred within 10 m of the seafloor. Average effective headrope heights for survey bottom trawls currently used in the eastern Bering Sea and Alaska Gulf/Aleutian Islands groundfish surveys are approximately 2.5 and 7 m, respectively. In the absence of any behavior responses to an approaching trawl, we would expect 47.3% of the cod within the water column are available to the trawl used on the eastern Bering Sea survey and 91.6% are available to the trawl used on the Gulf/Aleutian Islands surveys. This study demonstrated that Pacific cod are highly demersal, and current values of trawl survey catchability (Q) used in current stock assessments are consistent with estimates of cod availability to the trawl gear.     

The pelagic habitat analysis module for ecosystem‐based fisheries science and management

We have developed a set of tools that operate within an aquatic geographic information system to improve the accessibility, and usability of remote‐sensed satellite and computer‐modeled oceanographic data for marine science and ecosystem‐based management. The tools form the Pelagic Habitat Analysis Module (PHAM), which can be applied as a modeling platform, an investigative aid in scientific research, or utilized as a decision support system for marine ecological management. Applications include fisheries, marine biology, physical and biological oceanography, and marine spatial management. The GIS provides a home for diverse data types and automated tools for downloading remote sensed and global circulation model data. Within the GIS environment, PHAM provides a framework for seamless interactive four‐dimensional visualization, for matching between disparate data types, for flexible statistic or mechanistic model development, and for dynamic application of user developed models for habitat, density, and probability predictions. Here we describe PHAM in the context of ecosystem‐based fisheries management, and present results from case study projects which guided development. In the first, an analysis of the purse seine fishery for tropical tuna in the eastern Pacific Ocean revealed oceanographic drivers of the catch distribution and the influence of climate‐driven circulation patterns on the location of fishing grounds. To support management of the Common Thresher Shark (Alopias vulpinus) in the California Current Ecosystem, a simple empirical habitat utilization model was developed and used to dynamically predict the seasonal range expansion of common thresher shark based on oceanographic conditions.     

Habitat configuration for an obligate shallow‐water delphinid: The Indo‐Pacific humpback dolphin,Sousa chinensis,in the Beibu Gulf (Gulf of Tonkin)

1. Habitat configuration is an important baseline to delineate protected area design, refine impact mitigation measures and define habitat protection plans for threatened species. For coastal delphinids, outlining their habitat configuration becomes a real challenge when faced with large distribution ranges that straddle international borders, leaving broad information gaps in uninvestigated areas.
2. This study projected likely habitats of Indo‐Pacific humpback dolphins, Sousa chinensis, in the Beibu Gulf (Gulf of Tonkin) based on occurrence data and remotely sensed oceanographic characteristics. Net primary productivity was derived to measure the ecosystem service of humpback dolphin habitats.
3. Bathymetry and chlorophyll‐a concentration are major variables contributing to humpback dolphin habitat configuration, which is characterized by shallow water depth and high primary productivity. Three major, likely habitats were identified in the northern Beibu Gulf from western Leizhou Peninsula to the China–Vietnam border, western Gulf of Tonkin from the Red River estuary to the central coast of Vietnam, and south‐western Hainan Island. Less than 9% of likely habitats are currently protected by marine protected areas.
4. Affinity to high primary productivity and shallow depths implies that prey abundance and foraging efficiency influence habitat selection by Indo‐Pacific humpback dolphins. Anthropogenic activities potentially altering oceanographic characteristics may impact regional marine ecosystem functions, and hence habitat configuration.
5. Habitat protection actions for Indo‐Pacific humpback dolphins include implementing coordinated and systematic surveys in major habitats, associating core habitat protection with protected area networks and maritime function zoning, ensuring ecosystem function integrity within major habitats, and reducing both explicit lethal impacts and implicit anthropogenic impacts from activities that change oceanographic features. The habitat protection plan should not only consider marine habitats, but also adjacent coastal landscapes and river catchments. This requires coordination, collaboration and information sharing between scientific research teams, government policy representatives, non‐governmental organizations, local communities and other interested stakeholders.

     

Length and sex-specific associations between spiny dogfish (Squalus acanthias) and hydrographic variables in the Bay of Fundy and Scotian Shelf

The associations between spiny dogfish ( Squalus acanthias ) and hydrographic variables (temperature, salinity and depth) were examined in the Bay of Fundy and Scotian Shelf from 1970 to 1998. Data were obtained from standard groundfish bottom trawl surveys. Dogfish sex affected habitat associations. Males were found to occupy bottom water of significantly higher salinities and depths than that occupied by females. Length also significantly affected habitat associations. Smaller dogfish occupied relatively deep, high salinity bottom water compared with larger dogfish. Overall, the occupied temperatures, salinities and depths were significantly different from those which were available. Dogfish occupied warmer temperatures along a narrow range (6.62–9.19°C) compared with those which were available (1.57–9.35°C). Occupied salinity (32.70–34.43 ppt) and occupied depth (88.62–184.66 m) were also distributed along a narrower range than available salinity (32.16–34.79 ppt) and available depth (55.00–218.10 m). Sex-specific, length-specific and overall environmental preference by dogfish may bias traditional `offshore' groundfish surveys while large scale changes in hydrographic parameters may alter dogfish distribution and their interactions with other marine fauna.     

Distribution and intensity of bottom trawl fisheries in the Patagonian Shelf Large Marine Ecosystem and its relationship with marine fronts

Trawling is a major concern worldwide and there is considerable debate about its impact on marine ecosystems. The Patagonian Shelf Large Marine Ecosystem (PSLME) is an important fishing area in the Southwest Atlantic where bottom trawling is the dominant fishing method. We investigated the distribution of bottom trawl fishing within this region, defining the areas of highest trawling intensity (hotspots) and evaluating their relationship with marine fronts. We focused on the three main oceanographic fronts, the shelf‐break front, the southern Patagonia front and the mid‐shelf front. To estimate fishing effort and trawled areas, we used VMS data from 2006 to 2012. Despite being almost a fully trawlable shelf, we found that the spatial distribution of trawling activity is patchy and trawling hotspots were small, comprising annually <5% of the shelf extension or <7% of the total trawlable area. Contrary to what is believed worldwide, our findings suggest that over the PSLME the magnitude of habitat effects as a result of bottom trawling is relatively small. Regarding the three frontal systems studied, only the shelf‐break front showed a positive relationship with trawl fishing activity. Although trawling hotspots did not overlap with marine fronts, the shelf‐break front receives more trawling effort than expected. We hypothesize that this pattern is due to aggregation of species near or at the front taking advantage of the opportunities provided by this area.     

Evaluating impacts of fishing on benthic habitats: A risk assessment framework applied to Australian fisheries

Ecosystem-based management (EBM), in the context of fishing, considers impacts on all parts of an exploited marine ecosystem. Understanding the impacts of fishing on habitats is a necessary part of adopting EBM, but multi-scale data that describe the types and distributions of habitats, and the interactions of fishing with them, are typically limited or entirely lacking. An approach developed to address habitat impacts, and applied to all offshore bottom contact fisheries in Australian waters, forms part of a hierarchical risk assessment framework - the Ecological Risk Assessment for the Effects of Fishing (ERAEF). Its progressively quantitative hierarchical approach enables higher-risk interactions to be identified and prioritised in the early and intermediate assessment stages by screening out lower-risk interactions. The approach makes the best use of all available data, but it can also be inferential where data are lacking. At the intermediate level of the ERAEF, a semi-quantitative approach uses a general conceptual model of how fishing impacts on ecological systems, with a focus at the level of regional sub-fisheries defined by fishing method (gear type). A set of quantifiable attributes for habitats are used to describe the ‘susceptibility’ of each habitat to damage that may be caused by specific fishing gears; resilience is generalised as a habitat's inherent ‘productivity’ (ability to recover from damage). In the ERAEF, photographic imagery was used effectively to provide a standardised method to classify habitats, to visualise the attributes assessed, and to communicate with stakeholders. The application of the ERAEF to habitats is illustrated using results from a multi-sector fishery off southern Australia that has five primary sub-fisheries: two bottom trawl (‘otter trawler’ or ‘dragger’), bottom set auto-longline, bottom set gill net, and Danish seine. In the case of the otter trawl sub-fishery, a set of 158 habitat types was considered, of which 46, mostly on the outer continental shelf and slope, were identified as potentially higher risk and deserving management attention. Strengths of the ERAEF approach for benthic habitats include methodological flexibility and wide applicability, and in being interactive and inclusive - bringing stakeholders, scientists and managers together to ‘put habitat on the radar’ and to develop management solutions. Limitations include difficulties in construction and validation of scored attributes and scale dependence. In the context of ecological risk management, this method offers a way to assess risks to marine habitats in a rigorous, transparent, and repeatable manner.     

Modeled day–night biases in decapod assessment by bottom trawling survey

The activity rhythms of marine species may consistently bias demographic evaluation by bottom trawl survey, depending on the time of day. In this study, we examine occurrence data of selected commercial and non-commercial decapod species at different depths (0–800 m) of the western Mediterranean as produced by the Mediterranean international trawl survey (MEDITS) UE Program by sampling during daytime. In order to show how the activity rhythms and types of displacement (pelagic, nektobenthic and endobenthic) of different species can alter the occurrences determined by bottom trawling, and to quantify relative bias, we modeled potential outcomes of a putative nocturnal MEDITS sampling. MEDITS and published data for studies with 24-h hauls were compared in order to obtain a folding correction factor. We found that the temporal bias of sampling is moderate when trawling is performed on the continental slope and more important when it occurs on the continental shelf. The configuration of daytime and nighttime occurrence data by depth was performed using non-metric multidimensional scaling (nMDS). For the daytime configuration, association with irradiance (PAR) was evaluated by fitting occurrence data with a generalized additive model (GAM). Symmetry in species assemblages was found according to depth (inflection point at 200 m depth) as a significant irradiance-dependence distribution pattern of occurrences that took place on the shelf, above 200 m depth. For the night configuration, the inflection point relaxed due to the active displacements of some species, mixing the assemblages reported in daytime data. Results of the present study indicated that a deep knowledge of the autoecology of decapod species as it relates to activity rhythms (including a precise assessment of displacement typology) is of importance in population distribution and biomass evaluation and also influences locally perceived biodiversity. Accordingly, bottom trawl surveys for population assessment should take into account the timing of sampling as a factor potentially biasing obtained abundances.     

Examining the importance of consistency in multi-vessel trawl survey design based on the U.S. west coast groundfish bottom trawl survey

Generalized linear mixed-effects models can be used to combine bottom trawl data from multiple vessels, each with a different fishing power, into a single time series of relative abundance. However, how important might it be to have a consistent set of vessels and vessel characteristics from year to year given we can model differences in fishing power among vessels? We demonstrate how changes in the suite of fishing vessels performing the survey can affect the results of the data analysis using sablefish catches in the U.S. west coast groundfish bottom trawl survey from 1998 to 2000. The results do not indicate that one must have a consistent set of vessels over time to provide useful data, but rather that there is benefit to consistency even when the survey data are analyzed using advanced statistical models. Further research should be undertaken to quantify these benefits specifically to aid in contracting and bidding of survey vessels.     

底拖网资源调查的昼夜误差分析

利用１９８５和１９８６年秋季底拖网资源调查数据，分析了昼夜平均渔获量的差异，采用Ｂｒａｙ－Ｃｕｒｔｉｓ系数测量其不相似性。结果表明，除底层鱼类外，总平均和中上层鱼类平均渔获得昼液差显著，白天平均渔获量远高于晚上，特别是中上层鱼类相差１０余倍，主要种类的差异亦较大。     

黄河口两种鱼类资源密度不同估算方法的比较

以黄河口海域矛尾虾虎鱼(Chaeturichthys stigmatias)和短吻红舌鳎(Cynoglossus joyneri)两种鱼类为例,根据2013、2014年间4个季节月的调查数据,将Δ-分布模型法用于底拖网数据处理,比较基于模型和基于调查设计的两种方法在估算平均资源密度方面的差异,并初步探讨了影响Δ-分布模型法评估效果因素。结果表明,对于8月和10月的矛尾虾虎鱼调查数据,模型法估计的资源密度值小于设计法的估计值,根据其余6组数据计算的资源密度均为模型法更高,数据量和数据分布特征可能是影响Δ-分布模型评估结果的重要因素;8组数据计算所得方差模型法均明显低于设计法;极大值和零值对Δ-分布模型的评估结果有不同的影响。Δ-分布模型是一个稳健的模型,处理数据波动性更小,估计值具有更高的精确度,是一种适于底拖网数据处理和资源评估的模型。     

Essential fish habitats and hotspots of nekto‐benthic diversity and density in the western Mediterranean

1. Since the 1990s, most currently assessed Mediterranean nekto‐benthic stocks have been exploited above maximum sustainable yield and have declined. This study explores the co‐occurrence of essential fish habitats for the most important nekto‐benthic resources exploited by bottom‐trawl fisheries in the western Mediterranean and areas of importance for nekto‐benthic communities.
2. Fishery‐independent data obtained from Mediterranean scientific bottom‐trawl surveys were used to identify persistent hotspots of recruitment for the most important nekto‐benthic species around the Iberian Peninsula and the Balearic Islands between 2002 and 2016, as an indicator of their essential fish habitats. Likewise, hotspots of nekto‐benthic community diversity and density were also determined, as an estimate of key areas for nekto‐benthic communities.
3. Areas of overlap of persistent hotspots of recruitment and of community species richness and density were mainly found on the deep shelf and the upper slope (100–200 m and 200–500 m deep respectively).
4. These overlapping areas could be of particular interest in the development of fishery management plans aiming to implement an ecosystem approach to fisheries. Protection, through temporary or permanent closures, of the overlapping areas identified would contribute to improving both the sustainable exploitation of the main target species of bottom‐trawl fisheries and the conservation of nekto‐benthic communities.

     

Distribution and spawning dynamics of capelin (Mallotus villosus) in Glacier Bay, Alaska: a cold water refugium

Pacific capelin (Mallotus villosus) populations declined dramatically in the Northeastern Pacific following ocean warming after the regime shift of 1977, but little is known about the cause of the decline or the functional relationships between capelin and their environment. We assessed the distribution and abundance of spawning, non‐spawning adult and larval capelin in Glacier Bay, an estuarine fjord system in southeastern Alaska. We used principal components analysis to analyze midwater trawl and beach seine data collected between 1999 and 2004 with respect to oceanographic data and other measures of physical habitat including proximity to tidewater glaciers and potential spawning habitat. Both spawning and non‐spawning adult Pacific capelin were more likely to occur in areas closest to tidewater glaciers, and those areas were distinguished by lower temperature, higher turbidity, higher dissolved oxygen and lower chlorophyll a levels when compared with other areas of the bay. The distribution of larval Pacific capelin was not sensitive to glacial influence. Pre‐spawning females collected farther from tidewater glaciers were at a lower maturity state than those sampled closer to tidewater glaciers, and the geographic variation in the onset of spawning is likely the result of differences in the marine habitat among sub‐areas of Glacier Bay. Proximity to cold water in Glacier Bay may have provided a refuge for capelin during the recent warm years in the Gulf of Alaska.     

大连湾海域鱼类的群落结构研究

采用大连湾海域四季底拖网调查数据(2006年夏、冬季和2007年春、秋季),对其鱼类群落结构进行研究,并利用多样性指数法和丰度/生物量比较法(ABC曲线)评价鱼类群落受外界扰动的程度。研究结果表明,该海域四季共采集鱼类31种,隶属于10目24科31属,鱼类区系组成在适温性上以暖温性鱼类为主,在栖息水层上以底层鱼类为主。夏季鱼类生物量(43.16kg/h)和生物数量(950个/h)均明显高于其他3个季节。四季共有优势种为大泷六线鱼和许氏平鲉。鱼类群落多样性指数季节变化范围分别为物种丰富度指数0.76~2.16、多样性指数0.63~1.96、物种均匀度指数0.36~0.91。各季节间生物量和丰度组成的Bray-Curtis相似性均较高。多样性指数法和丰度/生物量曲线法对鱼类群落受外界扰动评价结果一致,均表明鱼类群落受到中度扰动,且秋冬季高于春夏季。本研究可为大连湾海湾生态系统健康评价和生态修复提供科学依据。     

东海区拖网新伏季休渔渔业生态和资源增殖效果的分析

为了更好地养护和合理利用海洋渔业资源,中国政府于2009年开始实施新的伏季休渔制度,其中从6月1日~9月15日在东海区禁止拖网作业,较原3个月的伏季休渔期提前增加半个月。本研究依据2006~2008年每年6月上半月拖网监测资料,从渔业生态和资源增殖的角度,着重分析研究拖网在6月上半月这一时段休渔的渔业生态效果和资源增殖效果。结果表明,6月上半月禁止拖网作业,主要养护了带鱼、小黄鱼和日本鲭等资源群体,并在一定程度上保护了带鱼的产卵亲体繁殖,对带鱼资源数量的补充起到了增殖作用,同时在较大程度上养护了带鱼和日本鲭幼鱼的自然生长,起到了资源增重作用,但对分布在拖网渔场外的小黄鱼幼鱼保护作用甚微。应用R icher动态综合模型估算,以带鱼为代表种,提前增加半个月伏季休渔期其资源增殖效果较以往3个月伏季休渔期可使年平均资源量增加11.86%,渔获量增加8.06%,平均渔获体重增加9.33%。东海区以拖网占捕捞主导地位的伏季休渔时间的延长,可进一步改善繁殖群体栖息地生态环境。     

南黄海族小黄鱼昼夜渔获率差异的统计学分析

利用2004年度东海区重点渔场底曳拖网渔业资源监测资料,从中选用小黄鱼网次渔获率作为指标值,应用LSD方法对南黄海族小黄鱼昼夜渔获率差异进行了统计学分析,以揭示小黄鱼昼夜的活动规律。结果表明,小黄鱼在不同的洄游阶段昼夜网次间渔获率无显著性差异,昼夜无垂直移动现象,常年处于底层,为典型的底层鱼类;在利用底曳拖网船进行渔业资源调查时,无需修正昼夜网次间小黄鱼的渔获率,用获取的调查数据即可估算资源量。     

Patchiness of eggs, larvae and juveniles of European hake Merluccius merluccius from the NW Mediterranean

We estimated patchiness for different life stages (egg, larvae and juveniles) of European hake (Merluccius merluccius) from two ichthyoplankton surveys (September and November 1999) and four bottom‐trawl surveys (November 1998, February, June and September 1999). Lloyd's patchiness P = 1 + 1/k, where k is the dispersion parameter of the negative binomial distribution, was calculated. Juveniles showed lower indices of patchiness than early ontogenetic stages. In juveniles, patchiness was highest for smaller size classes (3.5–5 cm TL) settling to their near‐bottom habitat and was very low for those larger than 5 cm up to the 30–35 cm size class (approximately 3 yr of age, 50% mature individuals). Patchiness of settling juveniles was especially high in the June and September surveys, coinciding with peak recruitment to the bottom. Both eggs and yolk sac larvae showed patchiness values <10, increasing in flexion stage larvae from 12 to 20. This pattern is different to that observed in other studies for pelagic species, where patchiness of early‐stage eggs is very high, but coincides with results obtained for other demersal species with pelagic eggs. Factors that may explain these patterns are discussed in light of oceanographic conditions, adult distribution and larval ontogenesis.     

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。     

Relative influence of static and dynamic features on black‐footed albatross (Phoebastria nigripes) habitat use in central California Sanctuaries

Effective conservation of highly mobile species requires an understanding of the factors that influence their habitat use patterns, locally and within a large‐scale oceanographic context. We characterized the seasonal (chick‐rearing, post‐breeding) and inter‐annual (2004–2008) distribution and abundance of black‐footed albatross (Phoebastria nigripes; BFAL) along the central California continental shelf/slope using standardized vessel‐based surveys. We used a hypothesis‐based information‐theoretic approach to quantify the relative influence of environmental conditions on BFAL occurrence and abundance by assessing their association with: (i) local static bathymetric features, (ii) local and regional dynamic oceanographic processes, and (iii) seasonal and inter‐annual basin‐wide variability. While the presence/absence models yielded stronger results than the abundance models, both revealed that static and dynamic features influence BFAL habitat use. Specifically, occurrence was greatest near the shelf‐break, particularly in months with strong upwelling. High BFAL densities were associated with Rittenburg Bank, especially during the chick‐rearing season, periods of positive North Pacific Gyre Oscillation index and large northern monthly upwelling, evidenced by cool, salty waters in the study area. BFAL aggregation intensity was greatest onshore of the shelf‐break (200 m isobath). Behavioral observations reinforced the notion that transiting BFAL are widely dispersed near the shelf‐break and concentrate in large flocks of birds sitting on the water farther onshore. These results underscore the need to consider oceanographic processes at multiple spatial scales when interpreting changes in BFAL dispersion within marine sanctuaries, and highlight the feasibility of implementing bathymetrically defined protected areas targeting predictable BFAL aggregations within these larger management jurisdictions.