Estimating fisheries reference points from catch and resilience

This study presents a Monte Carlo method (CMSY) for estimating fisheries reference points from catch, resilience and qualitative stock status information on data‐limited stocks. It also presents a Bayesian state‐space implementation of the Schaefer production model (BSM), fitted to catch and biomass or catch‐per‐unit‐of‐effort (CPUE) data. Special emphasis was given to derive informative priors for productivity, unexploited stock size, catchability and biomass from population dynamics theory. Both models gave good predictions of the maximum intrinsic rate of population increase r, unexploited stock size k and maximum sustainable yield MSY when validated against simulated data with known parameter values. CMSY provided, in addition, reasonable predictions of relative biomass and exploitation rate. Both models were evaluated against 128 real stocks, where estimates of biomass were available from full stock assessments. BSM estimates of r, k and MSY were used as benchmarks for the respective CMSY estimates and were not significantly different in 76% of the stocks. A similar test against 28 data‐limited stocks, where CPUE instead of biomass was available, showed that BSM and CMSY estimates of r, k and MSY were not significantly different in 89% of the stocks. Both CMSY and BSM combine the production model with a simple stock–recruitment model, accounting for reduced recruitment at severely depleted stock sizes.     

Considerations of stock structure of yellowfin tuna (Thunnus albacares) in the Indian Ocean based on fishery data

Yellowfin stock structure in the Indian Ocean was studied by using industrial tuna longline fishery data. Three types of test variables were used to detect stock structure, i.e., CPUE, age-specific CPUE, and coefficient of variation for size. Time-series data of test variables were compiled for six sub-areas that were arranged by dividing the whole region systematically along longitude lines every 20 degrees. Then time-series data were smoothed by moving averages, and regressed by simple models. Patterns of time-series trends were graphically and statistically compared to classify homogeneous sub-area groups. Two assumptions were (a) that homogeneous stocks exist longitudinally and overlap in adjacent waters, and (b) that test variables within homogeneous sub-area groups are equally affected, and hence patterns of the time-series trends are similar. After graphical screening for significant sub-area groups, analysis of covariance was applied to test homogeneity of regression parameters representing patterns of the time-series trends. By classifying homogeneous sub-area groups, stock structures were determined at the P <0.05 and P <0.50 levels. The P<0.50 level was recognized as a useful criterion for ‘weak’ test variables since masked or vague structures at the P <0.05 level were likely cleared at this level in many cases. Results of this study and past stock structure studies were reviewed and compared. It was concluded that there are two major and two minor stocks of yellowfin tuna. The two major stocks (the western and the eastern) are located at 40^o-90^oE and 70^o-130^oE respectively. The minor stocks are the far western and the far eastern stocks (the latter possibly being a part of the Pacific stock), which are located westward of 40^oE and eastward of 110^oE respectively. Neighboring stocks are intermingled in adjacent waters.     

Common trends in recruitment dynamics of north‐east Atlantic fish stocks and their links to environment,ecology and management

Recruitment dynamics are challenging to assess or predict because of the many underlying drivers that vary in their relevance over time and space. Stock size, demographic and trait composition, condition and distribution of spawning fish and the spatio‐temporal dynamics of trophic and environmental interactions all influence recruitment processes. Exploring common patterns among stocks and linking them to potential drivers may therefore provide insights into key mechanisms of recruitment dynamics. Here, we analysed stock‐recruitment data of 64 stocks from the north‐east Atlantic Ocean for common trends in variation and synchrony among stocks using correlation, cluster and dynamic factor analyses. We tested common trends in recruitment success for relationships with large‐scale environmental processes as well as stock state indicators, and we explored links between recruitment success and demographic, environmental and ecological variables for a subset of individual stocks. The results revealed few statistically significant correlations between stocks but showed that underlying common trends in recruitment success are linked to environmental indices and management indicators. Statistical analyses confirmed previously suggested relationships of environmental–ecological factors such as the subpolar gyre and Norwegian coastal current with specific stocks, and indicated a large relevance of spawning stock biomass and demographics, as well as predation, whereas other suggested relationships were not supported by the data. Our study shows that despite persistent challenges in determining drivers of recruitment due to poor data quality and unclear mechanisms, combining different data analysis techniques can improve our understanding of recruitment dynamics in fish stocks.     

Temperature-dependent stock-recruitment model for walleye pollock (Theragra chalcogramma) around northern Japan

Changes in fish year‐class strength have been attributed to year‐to‐year variability in environmental conditions and spawning stock biomass (SSB). In particular, sea temperature has been shown to be linked to fish recruitment. In the present study, I examined the relationship between sea surface temperature (SST), SSB and recruitment for two stocks of walleye pollock (Theragra chalcogramma) around northern Japan [Japanese Pacific stock (JPS) and northern Japan Sea stock (JSS)] using a temperature‐dependent stock‐recruitment model (TDSRM). The recruitment fluctuation of JPS was successfully reproduced by the TDSRM with February and April SSTs, and February SST was a better environmental predictor than April SST. In addition, the JPS recruitment was positively related to February SST and negatively to April SST. The JSS recruitment modeled by the TDSRM incorporating February SST was also consistent with the observation, whereas the relationship between recruitment and February SST was negative, that is the opposite trend to JPS. These findings suggest that SST in February is important as a predictor of recruitment for both stocks, and that higher and lower SSTs in February act favorably on the recruitment of JPS and JSS respectively. Furthermore, Ricker‐type TDSRM was not selected for either of the stocks, suggesting that the strong density‐dependent effect as in the Ricker model does not exist for JPS and JSS. I formulate hypotheses to explain the links between SST and recruitment, and note that these relationships should be considered in any future attempts to understand the recruitment dynamics of JPS and JSS.     

Variation in fish condition between Atlantic cod (Gadus morhua) stocks, the effect on their productivity and management implications

A comparative analysis of the fish condition (Fulton’s K) of 10 cod stocks in the north Atlantic in relation to the temperature of their habitat, growth rates and their reproductive potential is presented. It is shown that the cod stocks in the north Atlantic display different levels of mean condition, which is partly due to the different temperature regimes of their habitats. Cod living in colder waters, e.g. Greenland, Labrador and Grand Bank stocks, were found to be in poorer condition than cod living in warmer waters, e.g. North Sea and Irish Sea stocks.

Poor condition causes reduced productivity in terms of slow growth and low recruitment potential. Stocks in better condition display significantly higher weights at age 4 than stocks in poor condition. The a coefficients (function’s slopes) obtained from standardised Ricker’s recruitment–spawning stock biomass (SSB) relationships were defined as indicators for the recruitment potential of stocks. These a coefficients were found to be positively correlated with the mean condition factor of the 10 stocks analysed. This indicates that stocks consisting of individuals in poor condition appear to be very susceptible to reduced recruitment at low SSB, while the stocks that consist of fish in good condition seem to behave more robustly with a higher probability of good recruitment at low SSB. The positive effect of the cod condition on their reproductive potential generally implies that the stocks in good condition in the temperate regions of the northeast and west Atlantic can sustain higher exploitation rates than stocks in poor condition in the colder regimes of the northwest Atlantic (Greenland, Labrador and Grand Bank). This is confirmed by the positive relationship established between the estimated biological management reference points F_med and the mean cod condition factors, as well as by the recent status of these stocks.     

Linking Northeast Pacific recruitment synchrony to environmental variability

We investigated the hypothesis that synchronous recruitment is due to a shared susceptibility to environmental processes using stock–recruitment residuals for 52 marine fish stocks within three Northeast Pacific large marine ecosystems: the Eastern Bering Sea and Aleutian Islands, Gulf of Alaska, and California Current. There was moderate coherence in exceptionally strong and weak year‐classes and correlations across stocks. Based on evidence of synchrony from these analyses, we used Bayesian hierarchical models to relate recruitment to environmental covariates for groups of stocks that may be similarly influenced by environmental processes based on their life histories. There were consistent relationships among stocks to the covariates, especially within the Gulf of Alaska and California Current. The best Gulf of Alaska model included Northeast Pacific sea surface height as a predictor of recruitment, and was particularly strong for stocks dependent on cross‐shelf transport during the larval phase for recruitment. In the California Current the best‐fit model included San Francisco coastal sea level height as a predictor, with higher recruitment for many stocks corresponding to anomalously high sea level the year before spawning and low sea level the year of spawning. The best Eastern Bering Sea and Aleutian Islands model included several environmental variables as covariates and there was some consistent response across stocks to these variables. Future research may be able to utilize these across‐stock environmental influences, in conjunction with an understanding of ecological processes important across early life history stages, to improve identification of environmental drivers of recruitment.     

Density dependence in total egg production per spawner for marine fish

A paradigm of fisheries science holds that spawning stock biomass (SSB) is directly proportional to total egg production (TEP) of fish stocks. This “SSB–TEP proportionality” paradigm has been a basic premise underlying the spawner–recruitment models for fisheries management and numerous studies on recruitment mechanisms of fish. Studies on maternal effects on reproductive potential of a stock have progressed during the last few decades, leading to doubt concerning the paradigm. Nonetheless, a direct test of the paradigm at multidecadal scales has been difficult because of data limitations in the stock assessment systems worldwide. Here, we tested the paradigm for marine fish based on a novel combination of two independent 38‐year time series: fishery‐dependent stock assessment data and fishery‐independent egg survey data. Through this approach, we show that the SSB–TEP proportionality is distorted by density dependence in total egg production per spawner individual (TEPPS) or spawner unit weight (TEPPSW) at a multidecadal scale. The TEPPS/TEPPSW exponentially declined with biomass and thus was density‐dependent for Japanese sardine, a small pelagic species exhibiting a high level of population fluctuation, in the western North Pacific. By contrast, the TEPPS/TEPPSW was sardine‐density‐dependent for Japanese anchovy, another small pelagic species exhibiting a moderate level of population fluctuation well‐known for being out of phase with sardine. Our analysis revealed intraspecific (sardine) and interspecific (anchovy) density dependence in TEPPS/TEPPSW, which was previously unaccounted for in spawner–recruitment relationships. Such density‐dependent effects at the time of spawning should be considered in fisheries management and studies on recruitment mechanisms.     

丹江口水库太湖新银鱼不同繁殖群体的繁殖特征比较

2010年6月—2011年6月,对丹江口水库太湖新银鱼(Neosalanx taihuensis)不同繁殖群体的繁殖生物学特征进行了比较研究。结果表明:太湖新银鱼在该水库产卵时间为1—5月(春群)和9—10月(秋群);其中春季群体的体长(65.79 mm±6.05 mm)、性腺成熟指数(17.26±6.42)、繁殖力(1851粒±342粒)和成熟卵径(0.62 mm±0.05mm)均显著高于秋季群体(体长(55.04 mm±3.18 mm)、性腺成熟指数(11.72±5.01)、繁殖力(1 067粒±190粒)和成熟卵径(0.53 mm±0.04 mm))(P<0.05);但是两个群体的丰满度指数(101.43±19.71,101.87±11.85)差异并不显著(P>0.05)。春群是丹江口水库太湖新银鱼种群的主要补充者,春群管理与控制应是银鱼种群管理的重点。     

Ecosystem‐based forecasts of recruitment in two menhaden species

Gulf (Brevoortia patronus, Clupeidae) and Atlantic menhaden (Brevoortia tyrannus, Clupeidae) support large fisheries that have shown substantial variability over several decades, in part, due to dependence on annual recruitment. Nevertheless, traditional stock–recruitment relationships lack predictive power for these stocks. Current management of Atlantic menhaden explicitly treats recruitment as a random process. However, traditional methods for understanding recruitment variability carry the very specific hypothesis that the effect of adult biomass on subsequent recruitment occurs independently of other ecosystem factors such as food availability and predation. Here, we evaluate the predictability of menhaden recruitment using a model‐free approach that is not restricted by these strong assumptions. We find that menhaden recruitment is predictable, but only when allowing for interdependence of stock with other ecological factors. Moreover, while the analysis confirms the presence of environmental effects, the environment alone does not readily account for the complexity of menhaden recruitment dynamics. The findings set the stage for revisiting recruitment prediction in management and serve as an instructive example in the ongoing debate about how to best treat and understand recruitment variability across species and fisheries.     

Are stock assessment methods too complicated?

This critical review argues that several methods for the estimation and prediction of numbers‐at‐age, fishing mortality coefficients F, and recruitment for a stock of fish are too hard to explain to customers (the fishing industry, managers, etc.) and do not pay enough attention to weaknesses in the supporting data, assumptions and theory. The review is linked to North Sea demersal stocks. First, weaknesses in the various types of data used in North Sea assessments are summarized, i.e. total landings, discards, commercial and research vessel abundance indices, age‐length keys and natural mortality (M). A list of features that an ideal assessment should have is put forward as a basis for comparing different methods. The importance of independence and weighting when combining different types of data in an assessment is stressed. Assessment methods considered are Virtual Population Analysis, ad hoc tuning, extended survivors analysis (XSA), year‐class curves, catch‐at‐age modelling, and state‐space models fitted by Kalman filter or Bayesian methods. Year‐class curves (not to be confused with ‘catch‐curves’) are the favoured method because of their applicability to data sets separately, their visual appeal, simple statistical basis, minimal assumptions, the availability of confidence limits, and the ease with which estimates can be combined from different data sets after separate analyses. They do not estimate absolute stock numbers or F but neither do other methods unless M is accurately known, as is seldom true.     

Population reproductive potential: Evaluation of long-term stock productivity

In order to avoid recruitment overfishing, fish stocks must have sufficient reproductive ability. The spawning stock biomass (SSB), which ignores the value of immature fish, is widely used as an index of stock sustainability. From the perspective of sustainability, immediate reproduction, as well as future spawning, must be considered. We developed an index of long-term stock productivity, called the population reproductive potential (PRP). PRP is defined as the expected total reproductive value of the standing stock. We used PRP to assess the western Atlantic bluefin tuna (WBT) stock. The trends in SSB, numbers (N), biomass and PRP of WBT are inconsistent when compared to each other, due to fluctuation in age composition. We evaluated the long-term productivity of WBT by computer simulation and compared the result with trends in the abundance indices. The result of the computer simulation was highly consistent with the trend in the PRP. Short-term trends in SSB and N often do not reflect long-term stock trends, because they are highly sensitive to age-composition dynamics. The PRP is useful for evaluating stock trends, especially when the age composition is unstable.     

Comparison of factors affecting recruitment variability of walleye pollock Theragra chalcogramma in the Pacific Ocean and the Sea of Japan off northern Japan

The Japanese Pacific stock (JPS) and the northern Japan Sea stock (JSS) of walleye pollock Theragra chalcogramma are mainly distributed in the Pacific Ocean and the Sea of Japan off northern Japan, respectively. This paper summarizes and compares the factors affecting the recruitment variability of these two stocks. Spawning season is from December to March for both stocks. JPS recruitment has a positive relationship with the water temperature in January and February, whereas that of JSS has a negative relationship with the water temperature in January, February, and April. One possible reason for this is that pollock larvae have an optimum growth temperature of approximately 5 °C in the field. Drift of early life stages also appears to be an important influence on the recruitment of both stocks. Because the current generated by the northwest wind carries eggs of JPS into the main larval nursery ground, JPS recruitment is enhanced in years when the northwest wind is predominant in February. On the other hand, early life stages of JSS are transported into the nursery ground by the Tsushima Warm Current. However, this current also carries early life stages into the Sea of Okhotsk and offshore, resulting in poor JSS recruitment in years when this current is strong in March. In contrast to JPS, the recruitment of which is significantly impacted by cannibalism, young pollock have not been found in the stomachs of adult JSS. Warm temperatures in the Sea of Japan seem to induce the separation of young and adult pollock, and the shape of the stock–recruitment relationship also suggests that cannibalism is not important for JSS. Based on this knowledge, and on the hatch date distributions of larvae and juveniles, we propose mechanisms that can explain the recruitment fluctuations for JPS and JSS pollock.     

Correlations between circulating insulin-like growth factor-I and thyroxine and cortisol hormone levels,and some biometrical traits in female brood stocks during the late stages of sex maturation and in juvenile Persian sturgeon (<Emphasis Type="Italic">Acipenser persicus</Emphasis>)

Relationships between insulin-like growth factor-I (IGF-I) and thyroxine (T4) and cortisol hormones were studied in female brood stocks of Persian sturgeon [Acipenser persicus; caught from both sea water (SW) and fresh water (FW)] during late stages of sex maturation. A number of biometrical traits were also studied that could represent the reproductive and/or growth states of brood stocks, and the possible relationship between IGF-I and growth was assessed in juvenile Persian sturgeons between 1 and 4 years of age. IGF-I, T4 and cortisol were measured in serum samples using commercially available kits. A four-parameter logistic model test was performed between the standard curves and the sample dilutions for each hormone. Parallelism, linearity and regression coefficients for the linearized standard curves and serial dilutions of samples were not significantly different (P < 0.05). Serum IGF-I levels in the juveniles were higher than those in the SW brood stocks, and cortisol levels in the former were lower than those in both brood stocks (P < 0.05). T4 levels in serum samples of juveniles were below the detectable level. IGF-I concentrations in juveniles were correlated with total weight, total length and fork length, but they did not increase significantly with increasing age from 1 to 4 years old (P < 0.05). Compared with SW brood stock, the FW brood stock was younger, had a smaller girth, smaller polarization index and higher ova diameter (P < 0.05). There were no differences between IGF-I and T4 levels in the two brood stocks, but cortisol levels were significantly higher in the FW brood stock. Percentage of fertilization was correlated with serum IGF-I in both brood stocks (P < 0.05). Our results support a role for IGF-I during the juvenile growth and reproductive physiology in female brood stocks of the Persian sturgeon.     

青海湖裸鲤不同繁殖群体繁殖特性的比较研究

2017年7月~2018年6月,在青海湖的洱海、大湖、黑马河口、泉吉河口、沙柳河口和布哈河口6处采样点,共采集青海湖裸鲤(Gymnocypris przewalskii)繁殖群体样本295尾,对不同繁殖群体的繁殖特性进行比较研究。结果显示,除泉吉河口的性比(♀∶♂)<1(即0.82∶1)外,其余5个繁殖群体雌性个体数量均大于雄性(♀∶♂>1);6个繁殖群体的所有样本中,雌性的生物学最小型大于雄性。其中,雌性群体(布哈河口)的生物学最小型的年龄、全长和体重分别为5龄、157 mm和42.5 g,雄性(沙柳河口)为4龄、124 mm和24.5 g;6个繁殖群体的雌性性成熟系数(GSI)显著高于雄性(P<0.05),沙柳河口雌性GSI(19.67±1.36)%显著高于洱海(10.28±1.36)%和大湖(13.35±1.24)%(P<0.05),而不同繁殖群体雄性GSI间差异不显著(P>0.05);黑马河口平均绝对繁殖力Ft[(3338.18±324.25)粒]和相对繁殖力Fr[(21.88±2.10)粒/g]分别与沙柳河口的Ft[(10699.40±613.91)粒]和Fr[(82.68±4.63)粒/g]存在显著差异(P<0.05)。以上研究结果表明,青海湖裸鲤的繁殖特性在不同群体之间已出现分化趋势或已经分化。本研究可为进一步了解青海湖裸鲤的种群结构以及制定合理的渔业资源管理措施提供基础数据,特别是增殖放流策略的优化。     

Was historical cisco Coregonus artedi yield consistent with contemporary recruitment and abundance in Lake Superior?

Historically, cisco Coregonus artedi Lesueur was the predominant prey fish and target of commercial fisheries throughout Lake Superior, but most spawning stocks collapsed by the mid-1900s. Stocks partially recovered by the early 1990s, but contemporary abundance is considered to be below historical levels and driven by intermittent recruitment. Stochastic, age-structured simulation models were used to determine whether historical (pre-1955) cisco yield in Lake Superior was consistent with contemporary (1992–2015) abundance, life-history characteristics and recruitment dynamics. When compared to contemporary stocks, the findings suggest historical stocks had: (1) similar recruits per spawner at low spawning stock sizes; (2) lower rates of compensatory density dependence; (3) similar or lower recruitment variation depending on the area and (4) higher median adult and age-1 density. These findings are consistent with the hypothesis that eutrophication during the historical period supported greater recruitment and adult abundance and that re-oligotrophication during the contemporary period may be limiting full recovery.     

Examining common assumptions about recruitment: a meta‐analysis of recruitment dynamics for worldwide marine fisheries

Assumptions about the future productivity of a stock are necessary to calculate sustainable catches in fisheries management. Fisheries scientists often assume the number of young fish entering a population (recruitment) is related to the biomass of spawning adults and that recruitment dynamics do not change over time. Thus, managers often use a target biomass based on spawning biomass as the basis for calculating sustainable catches. However, we show recruitment and spawning biomass are not positively related over the observed range of stock sizes for 61% of 224 stocks in the RAM Legacy Stock Assessment Database. Furthermore, 85% of stocks for which spawning biomass may not drive recruitment dynamics over the observed ranges exhibit shifts in average recruitment, which is often used in proxies for target biomasses. Our results suggest that the environment more strongly influences recruitment than spawning biomass over the observed stock sizes for many stocks. Management often endeavours to maintain stock sizes within the observed ranges, so methods for setting management targets that include changes within an ecosystem may better define the status of some stocks, particularly as climate changes.     

Changes in spawning stock structure strengthen the link between climate and recruitment in a heavily fished cod (Gadus morhua) stock

Atlantic cod (Gadus morhua) is one of the commercially most important fish species in the North Atlantic and plays a central role in several ecosystems. Fishing pressure has been heavy over a prolonged period and the recent decades have shown dramatic decline in abundance of many stocks. The Arcto‐Norwegian (or North‐east Arctic) cod stock in the Barents Sea is now the largest stock of Atlantic cod. Recruitment to this stock has varied extensively during the last 60 yr. There is evidence for fluctuations in climate, particularly sea temperature, being a main cause for this variability, higher temperatures being favourable for survival throughout the critical early life stages. Our studies of time series present compelling evidence for a strengthening of the climate–cod recruitment link during the last decades. We suggest this is an effect of the age and length composition of the spawning stock having changed distinctly. The age of the average spawner has decreased by more than 3 yr from between 10 and 11 in the late 1940s to 7–8 in the 1990s, average length from just above 90 cm to around 80 cm. The number of age classes contributing to the spawning stock has also decreased, while the number of length groups present increased slightly. Significant decrease in age of spawners has frequently been described for other heavily fished stocks worldwide. We therefore find it likely that the proposed mechanism of increased influence of climate on recruitment through changes in the spawning stock age and size composition is of a general nature and might be found in other systems.     

The growth of larval cod and haddock in the Irish Sea: a model with temperature,prey size and turbulence forcing

We applied a physiological individual‐based model for the foraging and growth of cod (Gadus morhua) and haddock (Melanogrammus aeglefinus) larvae, using observed temperature and prey fields data from the Irish Sea, collected during the 2006 spawning season. We used the model to estimate larval growth and survival and explore the different productivities of the cod and haddock stocks encountered in the Irish Sea. The larvae of both species showed similar responses to changes in environmental conditions (temperature, wind, prey availability, daylight hours) and better survival was predicted in the western Irish Sea, covering the spawning ground for haddock and about half of that for cod. Larval growth was predicted to be mostly prey‐limited, but exploration of stock recruitment data suggests that other factors are important to ensure successful recruitment. We suggest that the presence of a cyclonic gyre in the western Irish Sea, influencing the retention and/or dispersal of larvae from their spawning grounds, and the increasing abundance of clupeids adding predatory pressure on the eggs and larvae; both may play a key role. These two processes deserve more attention if we want to understand the mechanisms behind the recruitment of cod and haddock in the Irish Sea. For the ecosystem‐based management approach, there is a need to achieve a greater understanding of the interactions between species on the scale a fish stock is managed, and to work toward integrated fisheries management in particular when considering the effects of advection from spawning grounds and prey–predator reversal on the recovery of depleted stocks.     

基于CMSY和BSM的东海区重要渔业种类资源评估

有限数据方法(data-limited method)可结合少量易获得数据和相关生物学信息对渔业资源状况、生物学参考点以及生物量等进行评估,已经成为全球区域性渔业管理组织和资源评估学者的关注热点。本研究采用基于渔获量的最大可持续渔获量(catch-based maximum sustainable yield,CMSY)和基于贝叶斯状态空间的Schaefer产量模型(Bayesian Schaefer production model,BSM)评估了东海区19个重要经济种类的资源状况,并提出了基于最大可持续渔获量(maximum sustainable yield,MSY)的渔业管理建议。结果显示,19个种类中有1个种类衰竭,3个种类严重衰退,5个种类过度捕捞,5个种类轻度过度捕捞,5个种类健康。种群状态长期评估结果表明,处于生物可持续水平的鱼类种群占比已由1980年的95%下降至2019年的26%。同时对CMSY和BSM方法的结果进行了比较,整合单位捕捞努力量渔获量(catch per unit effort,CPUE)数据的BSM方法导致了置信区间较宽,并调节了生物量轨迹的变化形态...     

Integrating seabird dietary and groundfish stock assessment data: Can puffins predict pollock spawning stock biomass in the North Pacific?

Information on the annual variability in abundance and growth of juvenile groundfish can be useful for predicting fisheries stocks, but is often poorly known owing to difficulties in sampling fish in their first year of life. In the Western Gulf of Alaska (WGoA) and Eastern Bering Sea (EBS) ecosystems, three species of puffin (tufted and horned puffin, Fratercula cirrhata, Fratercula corniculata, and rhinoceros auklet, Cerorhinca monocerata, Alcidae), regularly prey upon (i.e., “sample”) age-0 groundfish, including walleye pollock (Gadus chalcogramma, Gadidae) and Pacific cod (Gadus microcephalus, Gadidae). Here, we test the hypothesis that integrating puffin dietary data with walleye pollock stock assessment data provides information useful for fisheries management, including indices of interannual variation in age-0 abundance and growth. To test this hypothesis, we conducted cross-correlation and regression analyses of puffin-based indices and spawning stock biomass (SSB) for the WGoA and EBS walleye pollock stocks. For the WGoA, SSB leads the abundance of age-0 fish in the puffin diet, indicating that puffins sample the downstream production of the WGoA spawning stock. By contrast, the abundance and growth of age-0 fish sampled by puffins lead SSB for the EBS stock by 1–3 years, indicating that the puffin diet proxies incoming year class strength for this stock. Our study indicates connectivity between the WGoA and EBS walleye pollock stocks. Integration of non-traditional data sources, such as seabird diet data, with stock assessment data appears useful to inform information gaps important for managing US fisheries in the North Pacific.