Spawning Stock Biomass Research Articles

The Rosa Lee phenomenon and its consequences for fisheries advice on changes in fishing mortality or gear selectivity

Abstract When size-selective fishing removes faster-growing individuals at higher rates than slower-growing fish, the surviving populations will become dominated by slower-growing individuals. When this “Rosa Lee phenomenon” is ignored, bias may occur in catch and stock projections. In a length-and-age-based model we quantified the effects through simulations of a simplified fishery on a stock that resembles Western Baltic cod. We compared outcomes of runs with and without taking account of the Rosa Lee phenomenon in scenarios of changes in fishing mortality. We found that, when only fishing rate was changed, the biases in predictions of spawning-stock biomass (SSB), yield and catches of undersized fish were relatively small (<10% in absolute values). When the selectivity parameters of the gear were increased, the bias in the prediction of the catches of undersized fish was very substantial (+120 to 160%). When the selectivity parameters were decreased, the biases in the predictions of SSB, yield and catches of undersized fish, were substantial (25–50% in absolute values). With slower mean growth the biases became more pronounced. We conclude that in short-term forecasts, medium-term projections, and MSE simulations featuring selectivity changes, the Rosa Lee phenomenon should be accounted for, ideally by using length-based models.

Disentangling density‐dependent effects on egg production and survival from egg to recruitment in fish

AbstractUnderstanding of density‐dependent effects is key to achieving sustainable management of self‐regulating biological resources such as fish stocks. Traditionally, density‐dependent effects on population abundance in fish have been considered to occur from hatching to recruitment, based on the paradigm of proportionality between spawning stock biomass and total egg production. Here, we demonstrate how the existence of intraspecific and interspecific density dependence in egg production changes the current understanding of density‐dependent processes in the life history of fish, by disentangling density‐dependent effects on egg production and survival from egg to recruitment, using sardine (Sardinops melanostictus, Clupeidae) and anchovy (Engraulis japonicus, Engraulidae) as model species. For sardine, strong intraspecific density‐dependent effects occurred in egg production, but no density‐dependent effects occurred or if any they were weak enough to be masked by environmental factors from hatching to recruitment. In contrast, for anchovy, interspecific density‐dependent effects occurred in egg production. In the survival after hatching, anchovy experienced stronger intraspecific density‐dependent effects than currently recognized. This analysis could overturn the current understanding of density‐dependent effects in the life history, highlighting contrasts between the effects on individual quality and population abundance and between the model species. We propose to reconsider the basis of fisheries management and recruitment studies based on the revised understanding of density‐dependent effects in the life history of the respective species.

Multidecadal dynamics of the Arctic copepod Limnocalanus macrurus in relation to environmental variability in the Baltic Sea

Abstract The Arctic Limnocalanus macrurus is a prominent representative of large copepods which performs several essential functions in freshwater and marine ecosystems. Being a cold stenotherm species, its distribution is primarily confined to deeper water layers. Based on the long-term observations from one of the largest spatially confined natural populations of this species in the Baltic Sea, we detected profound long-term variability of L. macrurus during 1958–2016: high abundances before the 1980s, then nearly disappearance in the 1990s and recovery in the 2000s. The main environmental parameters explaining the interannual variability of L. macrurus in spring were herring spawning stock biomass in preceding year, winter severity, and bottom water temperature in preceding summer. The effect of winter severity and water temperature was also non-linear. The sliding window correlation analysis pointed to a non-stationary relationship between the abundance of L. macrurus and the key variables. Given the observed pronounced seasonality in the population structure of L. macrurus (young stages dominated in the beginning of the year and only adults were left in the population in summer and autumn) we identified the dynamics of key environmental variables to understand this species under different ecosystem configurations and different combinations of drivers of change.

The influence of spatially variable and connected recruitment on complex stock dynamics and its ecological and management implications

To evaluate the influence of spatially variable and connected recruitments at spawning component scale on complex stock dynamics, a typical agent-based complex stock was modeled based on the Atlantic cod (Gadus morhua) stock in the Gulf of Maine. We simulated three scenarios with different degrees of connectivity (i.e., individual exchange) between the spatially variable recruitments of 36 spawning components within four subpopulations under the stock. Subsequently, the temporal trends were compared for different scenarios in age-1 recruitment, spawning stock biomass, and local depletion proportion of the overall complex stock and the individual subpopulations. Results show that increased recruitment connectivity from 0.1–0.2 to 0.6–0.8 between various components tends to increase the productivity and stability of a complex stock at local and global scales and reduce the proportion of depleted components due to overfishing. Moreover, depletions of less productive components may occur without a substantial reduction in the overall complex stock biomass and recruitment.

Accounting for ocean connectivity and hydroclimate in fish recruitment fluctuations within transboundary metapopulations.

Marine resources stewardships are progressively becoming more receptive to an effective incorporation of both ecosystem and environmental complexities into the analytical frameworks of fisheries assessment. Understanding and predicting marine fish production for spatially and demographically complex populations in changing environmental conditions is however still a difficult task. Indeed, fisheries assessment is mostly based on deterministic models that lack realistic parameterizations of the intricate biological and physical processes shaping recruitment, a cornerstone in population dynamics. We use here a large metapopulation of a harvested fish, the European hake (Merluccius merluccius), managed across transnational boundaries in the northwestern Mediterranean, to model fish recruitment dynamics in terms of physics-dependent drivers related to dispersal and survival. The connectivity among nearby subpopulations is evaluated by simulating multi-annual Lagrangian indices of larval retention, imports, and self-recruitment. Along with a proxy of the regional hydroclimate influencing early life stages survival, we then statistically determine the relative contribution of dispersal and hydroclimate for recruitment across contiguous management units. We show that inter-annual variability of recruitment is well reproduced by hydroclimatic influences and synthetic connectivity estimates. Self-recruitment (i.e., the ratio of retained locally produced larvae to the total number of incoming larvae) is the most powerful metric as it integrates the roles of retained local recruits and immigrants from surrounding subpopulations and is able to capture circulation patterns affecting recruitment at the scale of management units. We also reveal that the climatic impact on recruitment is spatially structured at regional scale due to contrasting biophysical processes not related to dispersal. Self-recruitment calculated for each management unit explains between 19% and 32.9% of the variance of recruitment variability, that is much larger than the one explained by spawning stock biomass alone, supporting an increase of consideration of connectivity processes into stocks assessment. By acknowledging the structural and ecological complexity of marine populations, this study provides the scientific basis to link spatial management and temporal assessment within large marine metapopulations. Our results suggest that fisheries management could be improved by combining information of physical oceanography (from observing systems and operational models), opening new opportunities such as the development of short-term projections and dynamic spatial management.

Evaluating the Sustainability of a Cisco Fishery in Thunder Bay, Ontario, under Alternative Harvest Policies

AbstractSustainable management of fish stocks is promoted through the application of management strategy evaluations (MSEs), providing information to managers on the relative performance of alternative management approaches (strategies) while accounting for uncertainty. In this study, we developed a simplifiedMSEof a stock of CiscoCoregonus artediin Thunder Bay, Ontario, to determine both the sustainability of the current harvest control rule (i.e., a constant exploitation rate [U] of 10%) and the performance of alternative harvest control rules in meeting fishery objectives. Success in meeting fishery objectives was evaluated through attained yields, interannual variation in yields, magnitude of spawning stock biomass (SB), and the risk of reaching lowSB—performance metrics established based on consultation with an advisory group to Lake Superior fishery managers. Our simulations explicitly accounted for uncertainty in the frequency of strong year‐classes being produced by Cisco, the stock–recruit relationship, stock abundance, and the sex‐specific nature of roe harvest. Assuming that future productivity is similar to the productivity observed over the period from 1985 to 2015, results suggest that the currentUof 10% is sustainable in terms of maintainingSBabove 20% of the unfished level. Variants of constantUcontrol rules that included thresholds defining whenUis to decrease as a function ofSBincreased yield, decreased risk, and increased the magnitude ofSBat the end of the simulation period. However, these advantages came at the expense of greater interannual variation in yield. Constant catch control rules greatly underperformed constantUcontrol rules in terms of magnitude in yield; however, they did reduce interannual variation in yield compared to constantUcontrol rules. Furthermore, conditional versions of constant catch control rules (i.e., threshold stock sizes below which the catch limit was reduced) mitigated risks of staying at low stock size.

Developing and evaluating a management strategy evaluation framework for the Gulf of Maine cod (Gadus morhua)

Management strategy evaluation (MSE) is an effective tool to evaluate the performance of harvest control rules (HCRs) and alternative management strategies. However, a comprehensive MSE framework advising management is still absent for the severely depleted Gulf of Maine (GoM) cod (Gadus morhua). In the present study, we developed a conceptual MSE framework and conditioned on this stock utilizing stock-specific parameterization. We highlighted the simulation of a few key processes with semi-independent sub-models and accounted for uncertainties from multiple sources. The simulated population dynamics was calibrated and validated against the historical trend in hindcasting. Forecasting simulations were also conducted and validated to examine the effectiveness in the context of uncertainty. Hindcasting results suggested that the calibrated MSE framework could capture the stock dynamics assuming different recruitment dynamics indicated by residuals lower than 5%. Forecasting stochastic runs demonstrated a minor disparity between management effects of fishing-mortality-based and catch-based HCRs when the segregated stock recruitment relationship was adopted with a difference in simulated spawning stock biomass lower than 10%. Additionally, the results were comparable to assessment and projections made in the stock assessment, indicating the robustness of the framework. The framework can potentially help disentangle complex issues related to the mixed fishery, decision-making, and performance evaluation of a monitoring system.

Re-evaluation of the environmental dependence of Pacific sardine recruitment

The environment influences the recruitment of small pelagic fishes, so environmental indices are used to match fishing mortalities to the stocks’ productivities. For example, the exploitation fraction for the northern stock of Pacific sardine in the Northeastern Pacific is a function of sea-surface temperature (SST). The functional relationship changes, however, because our perception of the environmental effects on sardine recruitment is based on assessment models that are periodically updated with new input data and assumptions. In this paper, we use data from recent stock assessments to re-examine previously identified correlations of sardine recruitment success (the logarithmic ratio of recruitment and spawning stock biomass) with indices of SST off Southern California and the Pacific Decadal Oscillation (PDO). We show that the earlier correlation with SST is likely invalid, and the persistent correlation with the PDO is weaker. Because many environmental stock-recruitment relationships fail upon re-examination, environmental proxies for fish productivity might not always prescribe the correct amount of fishing mortality and should be avoided. Alternatively, for species assessed periodically, dynamic fishing mortalities could be based on measurements of recent stock productivity inferred directly from surveys, or from the results of analytical assessments based on those observations.

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

AbstractRecruitment 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.

Simple Modeling to Inform Harvest Strategy Policy for a Data‐Moderate Crab Fishery

AbstractAttempts to model the giant mud crab Scylla serrata fishery in the Northern Territory (Australia), have often been complex and the results difficult to interpret, leading to divergent estimates of fishing mortality. This has hindered the development of meaningful management policy. Additionally, analyses based on the entire Northern Territory fishery have masked the extreme variation in catches observed along the Gulf of Carpentaria coast. We applied a structurally simple model to visualize the historical patterns in stock size, recruitment, fishing mortality, and fishing mortality at maximum sustainable yield in the western Gulf of Carpentaria mud crab fishery (WGOCMCF) from 1983 to 2017. We also projected future catch and female spawning stock biomass (FSSB) under positive, neutral, and negative recruitment scenarios for three closure periods contained in the fishery harvest strategy (which start in October, if triggered) and compared these with the results of equivalent closures beginning in September. This exercise was undertaken because of known and significant changes in the proportion of fishing effort across different months as well as large variations in the proportion of females harvested each month (with both factors being particularly low in December). These differences were annualized and incorporated into the yearly time step of the model. Predicted catch and FSSB were similar for shorter closure periods (3 or 6 weeks), irrespective of the starting month. However, initiating a 3‐month closure in September rather than October could lead to a 16–17% increase in FSSB under negative and average recruitment anomalies, imposing a 9–10% reduction in predicted catch. Based on our experience applying a simple model to the WGOCMCF, we also describe processes and practices that could improve the quality of assessment data for this and other data‐moderate crab fisheries.

Digital Image Analysis as a Technique for Alewife Fecundity Estimation in a New Hampshire River

AbstractFecundity estimates are important in fisheries management to determine the reproductive potential and spawning stock biomass of a population. Traditional methods for determining these estimates, however, have been time consuming and tedious, often requiring long‐term sample storage in toxic preservatives. Recently, studies incorporated the use of scanners and image analysis software to produce equally reliable fish fecundity estimates. This study was undertaken to demonstrate the application of this technique with Alewife Alosa pseudoharengus, “a species of concern.” Ovaries were collected from fish ranging in size from 25 to 34 cm throughout their annual spawning migration (Newmarket, New Hampshire) and used to compare fecundity estimated gravimetrically following long‐term storage and by use of a flatbed scanner. Gonadosomatic indices were calculated throughout the collection period but were not found to differ over time. Comparisons within ovaries demonstrated that oocyte size and number did not differ among anterior, center, and posterior sections. Fecundity estimates did not differ between the two methods and increased with fish age and size ranging from 121,000 and 130,200 oocytes/female (25 cm) to 332,500 and 364,900 oocytes/females (34 cm), respectively. These results demonstrate that fecundity estimates using digital image analysis software were equally reliable as those produced by traditional methods but were generated more quickly and with less reliance on toxic preservatives.

Evaluating Summer Flounder Spatial Sex‐Segregation in a Southern New England Estuary

AbstractMarine fish species can exhibit sex‐specific differences in their biological traits. Not accounting for these characteristics in the stock assessment or management of a species can lead to misunderstanding its population dynamics and result in ineffective regulatory strategies. Summer Flounder Paralichthys dentatus, a flatfish that supports significant commercial and recreational fisheries along the northeastern U.S. shelf, expresses variation in several traits between the sexes, including growth and habitat preference. To further understand these patterns, 1,302 Summer Flounder were collected and sexed in 2016 and 2017 from fisheries‐independent surveys conducted in Rhode Island state waters. Female flounder were more prevalent in shallow waters (≤15 m) through all months, but males had a greater presence in deeper waters (>15 m) from May through September. The probability of a collected flounder being female was evaluated with generalized linear models and covariates representing depth, temperature, month, year, and TL. Summer Flounder were more likely to be female at larger sizes, in shallower waters, and late in the season. When compared with landings data in the recreational fishery over the sampling period, the results suggest that nearly all flounder harvested in the sector were female. This work provides further evidence for and characterization of Summer Flounder sex‐segregation and highlights, for management purposes, the importance of considering fine‐scale spatial dynamics in addition to broader distribution patterns. The fitted model represents an effective first step toward understanding the implications of an aggregated fishing effort for disproportionate removals of male or female flounder and for exploring resulting consequences for regional spawning stock biomass and stock resiliency.

Model uncertainty and simulated multispecies fisheries management advice in the Baltic Sea.

Different ecosystem models often provide contrasting predictions (model uncertainty), which is perceived to be a major challenge impeding their use to support ecosystem-based fisheries management (EBFM). The focus of this manuscript is to examine the extent of model disagreements which could impact management advice for EBFM in the central Baltic Sea. We compare how much three models (EwE, Gadget and a multispecies stock production model) differ in 1) their estimates of fishing mortality rates (Fs) satisfying alternative hypothetical management scenario objectives and 2) the outcomes of those scenarios in terms of performance indicators (spawning stock biomasses, catches, profits). Uncertainty in future environmental conditions affecting fish was taken into account by considering two seal population growth scenarios and two nutrient load scenarios. Differences in the development of the stocks, yields and profits exist among the models but the general patterns are also sufficiently similar to appear promising in the context of strategic fishery advice. Thus, we suggest that disagreements among the ecosystem models will not impede their use for providing strategic advice on how to reach management objectives that go beyond the traditional maximum yield targets and for informing on the potential consequences of pursuing such objectives. This is especially true for scenarios aiming at exploiting forage fish sprat and herring, for which the agreement was the largest among our models. However, the quantitative response to altering fishing pressure differed among models. This was due to the diverse environmental covariates and the different number of trophic relationships and their functional forms considered in the models. This suggests that ecosystem models can be used to provide quantitative advice only after more targeted research is conducted to gain a deeper understanding into the relationship between trophic links and fish population dynamics in the Baltic Sea.

Multivariate determination of Atlantic herring population health in a large marine ecosystem

Abstract Atlantic herring are among the most harvested marine fish species globally and are of extraordinary ecological and economic importance. Within the Scotian Shelf and Bay of Fundy management zone (NAFO Division 4WX), herring support one of the largest fisheries in Canada, yet the conservation status of the stock is currently unclear. We use field observations, stock assessments, and published studies to evaluate the long-term (1965–2016) status, or health, of 4WX Atlantic herring based on 33 indicators that serve as proxies for the ecological dynamics across the larval, juvenile, and adult stages. Sixteen indicators that showed evidence of significant and synchronous temporal changes were integrated to produce a standardized series of herring population health. This multivariate index exhibited a gradual, long-term decline punctuated by a more rapid decline between 1980 and 2005. Following normalization, future trajectories of herring spawning stock biomass (SSB) over this period were best forecast by the average weight of herring (r2 = 0.63; lag = 6 years) and indicated that SSB would remain low over the next 6 years. Our study suggests that integrating factors related to population health can provide deeper insight in situations where individual series are uncertain and can complement existing assessment approaches.

Stock collapse or stock recovery? Contrasting perceptions of a depleted cod stock

Abstract ICES assessments of cod (Gadus morhua) in the west of Scotland (ICES Division 6a) suggest the biomass has collapsed and that fishing mortality rate (F) has remained high. In contrast, other stocks in the same fishery, and adjacent cod stocks all show marked declines in fishing mortality and some recovery of the biomass. The perception of the status of 6a cod appears to be dependent on the assumption that the fishery exploitation pattern is flat topped. An assessment that allows the exploitation to take a domed shape produces results that suggest a marked decline in fishing mortality rate and that the spawning stock biomass has recovered to the minimum biomass reference point, Blim. The reduction in F is consistent with substantial reductions in fishing effort and shows a similar pattern to stocks taken within the same fishery. The management implications arising from the two assessments differ substantially. The analysis indicates that benchmark assessments need to test assessment model conditioning assumptions more widely and that management advice needs to consider a more comprehensive range of information about the stock and fishery.

An assessment of European bream Abramis brama (Linnaeus, 1758) fishery in the downstream of the Irtysh River in China

Per-recruit analyses, with consideration for uncertainty in growth, natural mortality and maturity, were conducted for European bream Abramis brama in the downstream section of the Irtysh River in China to assess its status. The Chapman-Robson method produced an estimate of total mortality rate (Z) of 0.65 year−1. The natural mortality rates (M) were estimated as 0.13 and 0.26 year−1, resulting in corresponding estimates of current fishing mortality rate (Fcur) of 0.52 and 0.39 year−1, respectively. All the estimates of yield per recruit (YPR), spawning stock biomass per recruit (SSB/R) and corresponding biological reference points (BRPs) were sensitive to M. The uncertainty of growth and maturity parameters had limited impacts on the estimates of BRPs, but had a large effect on the YPR and SSB/R outputs. Our findings indicate that A. brama may be at higher risk of growth overfishing than those of recruitment overfishing. In addition, increasing the tc to nine years might ensure that the spawning potential ratios (SPRs) are above the management targets under all ranges of F with comparatively small impacts on YPR regardless of M. In addition to providing a basic assessment for A. brama in the downstream of the Irtysh River in China, our study presents a comprehensive approach that may be useful for data-limited species in other fisheries.

Spatial management of the European hake <em>Merluccius merluccius</em> fishery in the Catalan Mediterranean: Simulation of management alternatives with the InVEST model

European hake (Merluccius merluccius) is an important commercial fisheries species that shows growth overfishing, with catches basically focused on juveniles. This study assesses the benefit of closing a coastal area (an essential habitat for European hake recruits) to fishing, in addition to other alternatives of spatial management, compared with traditional, non–spatial management scenarios on fishing grounds exploited by the bottom trawl fleets of Blanes and Palamós (Province of Girona, NE Spain). We use InVEST, a spatially explicit model of intermediate complexity that simulates the bioeconomic effects of management measures for decision making. The sensitivity analysis of the model results shows the high influence of some parameters, particularly the parameterization of the recruitment submodel and European hake’s fecundity coefficients. The results are also examined in the light of uncertainty on migration parameters: in the two cases analysed (considering migration patterns or not), the results of the indicators (catch and revenues, abundance, recruitment and spawning stock biomass) were qualitatively similar and all show that the application of a restricted fishing area in one particular fishing ground (Vol de Terra) is the best management alternative. Its bioeconomic effects are comparable to a reduction of fishing effort of up to 20%. With high levels of ontogenetic migration, fishing on a second fishing ground (Cul de Rec – El Pas) should be restricted to enhance the biomass of the European hake population.

Assessment of the Relationship of Stock and Recruitment in the Atlantic Surfclam Spisula solidissima in the Northwestern Atlantic Ocean

Atlantic surfclams support a major commercial fishery in the western North Atlantic Ocean with landings consistently between 15,000 and 25,000 metric tons since 1982. The stock is not and historically has not been overfished nor has overfishing occurred; however, in recent years landings per unit effort have declined. Surfclams are a biomass dominant on the continental shelf and a bellwether of climate change in the northwestern Atlantic. This study investigated the relationship of broodstock and recruitment during a period when Mid-Atlantic warming initiated a shelf-wide shift in the surfclams range. A species distribution function model was used to assess the effective area occupied by surfclams for five study regions (Delmarva, New Jersey, Long Island, Southern New England, and Georges Bank). The effective area occupied by small surfclams was consistently much greater than that for large (≥120 mm) surfclams. Three independent statistical analyses of the stock-recruitment relationship found little evidence of a significant association in any of the five regions, suggesting that factors besides spawning stock biomass (SSB) are primary determinants of recruitment success. Interannual variability in recruitment, in part associated with variations in larval transport and in part associated with spatially different rates of mortality post-settlement, is an important source of uncertainty and warming bottom waters driving surfclams into new habitat may decouple any inherent interaction between recruits and SSB. A recruitment index obtained from a fishery-independent survey across the range of the stock, as a consequence, is unlikely to usefully presage changes in abundance of the fishable stock. The wider distribution of settlers relative to the fishable stock, however, positions the species well to respond to changing bottom water temperatures as Mid-Atlantic warming continues.

Can spawning origin information of catch or a recruitment penalty improve assessment and fishery management performance for a spatially structured stock assessment model?

We used simulations based on lake whitefish (Coregonus clupeaformis) populations to explore the benefits of using spawning origin information for parsing catch to spawning populations in stock assessments for intermixed fisheries exhibiting an overlapping movement strategy. We compared this origin-informed assessment model with a standard assessment model that did not parse catch. We additionally evaluated the influence of including annual recruitment penalties. For standard assessment models, spawning stock biomass estimates could be unstable and biased (sometimes by more than 50%), depending upon population mixing and productivity, and in some cases estimated near average zero recruitment in the terminal year. Incorporating information on population-specific harvest age composition improved spawning stock biomass estimation (e.g., by sometimes essentially removing 50% biases and improving accuracy). Assessments with recruitment penalties produced less biased terminal recruitment estimates (sometimes a 100% bias was removed). Under status quo target mortality rates, improvements in assessments did not necessarily translate to improved fishery management performance (e.g., avoiding depletion of spawning biomass), but such improvements, and overall better performance, were seen at lower target mortality rates.

Synchronous multi-species alternations between the northern Humboldt and Kuroshio Current systems

Synchrony of species alternations in the northern Humboldt (NHCS) and Kuroshio (KCS) Current systems was examined by comparing time series data of landings and population statistics of major small pelagic fish species along with climate indices from 1960 to 2015. Target species were anchovy Engraulis ringens, sardine Sardinops sagax, jack mackerel Trachurus murphyi and chub mackerel Scomber japonicus in the NHCS, and anchovy E. japonicus, sardine S. melanostictus, jack mackerel T. japonicus and chub mackerel in the KCS. The time series of total biomass and spawning stock biomass (SSB) of anchovy and sardine for the NHCS and the KCS were well correlated, as were the landings data. Landings of small pelagic fish including jack mackerel and chub mackerel indicated that multi-species alternations may also be synchronous at a community level between the two current systems. Peak landings of jack mackerel and chub mackerel were observed between peaks of anchovy and sardine in both current systems, although the relationships between jack mackerel and chub mackerel differed between the current systems. The species alternations between anchovy and sardine are most reasonably attributable to environmentally-induced changes in the biomass as a major mechanism, although the effect of fishing activity cannot be excluded. Future studies will be required to compare biological characteristics of multiple small pelagic fish species in the pelagic food chain in each current system.