Marine Fish Recruitment Research Articles

Contrasting links between growth and survival in the early life stages of two flatfish species

Understanding the causes of variation in recruitment of marine fishes has been a central goal over the last century. However, the relationship between year class strength and larval growth and survival is poorly known for most species. The main goal of this study was to investigate the relationships between larval traits and year class strength of two flatfish species in an nursery estuary. We examined the effects of the variation in the early life characteristics (pelagic larval growth, pelagic larval duration, size-at-hatching and size-at-settlement) on post-settlement survival of flounder Platichthys flesus and common sole Solea solea in the Mondego estuary (Portugal) over a 5-year period (2011–2015). The two flatfish species showed distinct larval traits variation during the study period, mainly related with location of the spawning ground and intrinsic biologic patterns. Flounder was able to delay metamorphosis while gathering energy and/or waiting for suitable environmental cues from estuarine origins while sole take advantage of better environmental conditions due to a later hatching. Early fast growth were strongly related with subsequent growth, affecting larval survival. Both growth and larval traits variation during the studied period were strongly related with temperature. This study highlights the importance of early growth for fish survival and contributes with key information on fish early life stages that will support a better management of fish stocks.

Climate change impacts on mismatches between phytoplankton blooms and fish spawning phenology.

Substantial interannual variability in marine fish recruitment (i.e., the number of young fish entering a fishery each year) has been hypothesized to be related to whether the timing of fish spawning matches that of seasonal plankton blooms. Environmental processes that control the phenology of blooms, such as stratification, may differ from those that influence fish spawning, such as temperature-linked reproductive maturation. These different controlling mechanisms could cause the timing of these events to diverge under climate change with negative consequences for fisheries. We use an earth system model to examine the impact of a high-emissions, climate-warming scenario (RCP8.5) on the future spawning time of two classes of temperate, epipelagic fishes: "geographic spawners" whose spawning grounds are defined by fixed geographic features (e.g., rivers, estuaries, reefs) and "environmental spawners" whose spawning grounds move responding to variations in environmental properties, such as temperature. By the century's end, our results indicate that projections of increased stratification cause spring and summer phytoplankton blooms tostart 16days earlier on average (±0.05days SE) at latitudes >40°N. The temperature-linked phenology of geographic spawners changes at a rate twice as fast as phytoplankton, causing these fishes to spawn before the bloom starts across >85% of this region. "Extreme events," defined here as seasonal mismatches >30days that could lead to fish recruitment failure, increase 10-fold for geographic spawners in many areas under the RCP8.5 scenario. Mismatches between environmental spawners and phytoplankton were smaller and less widespread, although sizable mismatches still emerged in some regions. This indicates that range shifts undertaken by environmental spawners may increase the resiliency of fishes to climate change impacts associated with phenological mismatches, potentially buffering against declines in larval fish survival, recruitment, and fisheries. Our model results are supported by empirical evidence from ecosystems with multidecadal observations of both fish and phytoplankton phenology.

Forecasting future recruitment success for Atlantic cod in the warming and acidifying Barents Sea.

Productivity of marine fish stocks is known to be affected by environmental and ecological drivers, and global climate change is anticipated to alter recruitment success of many stocks. While the direct effects of environmental drivers on fish early life stage survival can be quantified experimentally, indirect effects in marine ecosystems and the role of adaptation are still highly uncertain. We developed an integrative model for the effects of ocean warming and acidification on the early life stages of Atlantic cod in the Barents Sea, termed SCREI (Simulator of Cod Recruitment under Environmental Influences). Experimental results on temperature and CO2 effects on egg fertilization, egg and larval survival and development times are incorporated. Calibration using empirical time series of egg production, temperature, food and predator abundance reproduces age-0 recruitment over three decades. We project trajectories of recruitment success under different scenarios and quantify confidence limits based on variation in experiments. A publicly accessible web version of the SCREI model can be run under www.oceanchange.uni-bremen.de/;SCREI. Severe reductions in average age-0 recruitment success of Barents Sea cod are projected under uncompensated warming and acidification toward the middle to end of this century. Although high population stochasticity was found, considerable rates of evolutionary adaptation to acidification and shifts in organismal thermal windows would be needed to buffer impacts on recruitment. While increases in food availability may mitigate short-term impacts, an increase in egg production achieved by stock management could provide more long-term safety for cod recruitment success. The SCREI model provides a novel integration of multiple driver effects in different life stages and enables an estimation of uncertainty associated with interindividual and ecological variation. The model thus helps to advance toward an improved empirical foundation for quantifying climate change impacts on marine fish recruitment, relevant for ecosystem-based assessments of marine systems under climate change.

Birds as major predators of fishes in the East Kleinemonde Estuary

This study provides a quantitative account of fish predation by piscivorous birds in the temporarily open/closed East Kleinemonde Estuary and represents the first global attempt to simultaneously relate such consumption to production by a fish community in the same estuary. Cormorants and herons were the dominant predators and seasonal variations in the avifaunal community composition were noted. Based on comprehensive counts over three years, the piscivorous bird population was estimated to have consumed a maximum of 4 414 kg of fish in 1994, 2 400 kg in 1995/96 and 2 960 kg in 2004/05. In 1995/96 fish production in the East Kleinemonde Estuary (55.89 g m−2 a−1) was estimated at 9 780 kg and maximum bird predation amounted to 25% of annual fish production within the system over the same period, assuming that all birds counted on the estuary foraged there and that the diet of these birds comprised only fish. The above 1995/96 figures, together with an estimate of fish predation by the dominant piscivorous fish Lichia amia of 696 kg suggests that birds are probably the single most important natural predator of fishes within this estuary. An unusual mass invasion by marine Cape Cormorants Phalacrocorax capensis during July 1994 was responsible for large-scale predation of fish (2 155 kg) and resulted in the population of estuary-associated marine fishes declining from approximately 63 300 to about 18 600 individuals during the 1994 closed phase. Given that little or no marine fish recruitment was possible while the estuary mouth was closed, piscivorous birds are likely to have a higher predatory impact on populations of juvenile marine fishes in small temporarily closed estuaries than in larger permanently open systems.

Oogenesis and reproductive investment of Atlantic herring are functions of not only present but long-ago environmental influences as well

Following general life history theory, immediate reproductive investment (egg mass × fecundity/body mass) in oviparous teleosts is a consequence of both present and past environmental influences. This clarification questions the frequent use of season-independent (general) fecundity formulas in marine fish recruitment studies based on body metrics only. Here we test the underlying assumption of no lag effect on gametogenesis in the planktivorous, determinate-fecundity Atlantic herring (Clupea harengus) displaying large plasticity in egg mass and fecundity, examining Norwegian summer-autumn spawning herring (NASH), North Sea autumn-spawning herring (NSAH), and Norwegian spring-spawning herring (NSSH). No prior reproductive information existed for NASH. Compared with the 1960s, recent reproductive investment had dropped markedly, especially for NSAH, likely reflecting long-term changes in zooplankton biography and productivity. As egg mass was characteristically small for autumn spawners, although large for spring spawners (cf. different larval feeding conditions), fecundity was the most dynamic factor within reproductive investment. For the data-rich NSSH, we showed evidence that transient, major declines in zooplankton abundance resulted in low fecundity over several subsequent seasons, even if Fulton's condition factor (K) turned high. Temporal trends in Kslope (K on total length) were, however, informative. These results clarify that fecundity is defined by (i) dynamics of primary (standing stock) oocytes and (ii) down-regulation of secondary oocytes, both processes intimately linked to environmental conditions but operating at different timescales. Thus, general fecundity formulas typically understate interannual variability in actual fecundity. We therefore argue for the use of segmented fecundity formulas linked to dedicated monitoring programs.

Unravelling the Gordian knot! Key processes impacting overwintering larval survival and growth: A North Sea herring case study

Unraveling the key processes affecting marine fish recruitment will ultimately require a combination of field, laboratory and modelling studies. We combined analyzes of long-term (30-year) field data on larval fish abundance, distribution and length, and biophysical model simulations of different levels of complexity to identify processes impacting the survival and growth of autumn- and winter-spawned Atlantic herring (Clupea harengus) larvae. Field survey data revealed interannual changes in intensity of utilization of the five major spawning grounds (Orkney/Shetland, Buchan, Banks north, Banks south, and Downs) as well as spatio-temporal variability in the length and abundance of overwintered larvae. The mean length of larvae captured in post-winter surveys was negatively correlated to the proportion of larvae from the southern-most (Downs) winter-spawning component. Furthermore, the mean length of larvae originating from all spawning components has decreased since 1990 suggesting ecosystem-wide changes impacting larval growth potential, most likely due to changes in prey fields. A simple biophysical model assuming temperature-dependent growth and constant mortality underestimated larval growth rates suggesting that larval mortality rates steeply declined with increasing size and/or age during winter as no match with field data could be obtained. In contrast better agreement was found between observed and modelled post-winter abundance for larvae originating from four spawning components when a more complex, physiological-based foraging and growth model was employed using a suite of potential prey field and size-based mortality scenarios. Nonetheless, agreement between field and model-derived estimates was poor for larvae originating from the winter-spawned Downs component. In North Sea herring, the dominant processes impacting larval growth and survival appear to have shifted in time and space highlighting how environmental forcing, ecosystem state and other factors can form a Gordian knot of marine fish recruitment processes. We highlight gaps in process knowledge and recommend specific field, laboratory and modelling studies which, in our opinion, are most likely to unravel the dominant processes and advance predictive capacity of the environmental regulation of recruitment in autumn and winter-spawned fishes in temperate areas such as herring in the North Sea.

Are the Laurentian Great Lakes great enough for Hjort?

Abstract Hjort's insights on marine fish recruitment and larval fish advection are presumed not applicable to freshwater lakes because most freshwater lakes are small. The Laurentian Great Lakes (LGL), however, are large enough for certain oceanic-type hydrodynamics, such as strong currents and upwelling, to affect the distribution and survival of larval fish and thus fall under Hjort's purview. However, there are evolutionary constraints because LGL species underwent an evolutionary bottleneck during glaciation, ∼10 000 years BP. We consider three narratives pertinent to both the spatial scale and the evolutionary time-scale of the LGL. The first reviews recent evidence of offshore advection and subsequent cross-lake dispersal of larval and juvenile yellow perch, a coastal demersal species in Lake Michigan. The second narrative suggests that biotic interactions, rather than spatial scale itself, could account for the transition in the critical period of Lake Michigan yellow perch period from a juvenile to a larval critical period. In the third narrative, we consider whether the deep LGL lack a significant native pelagic larval fish predator. We propose that the LGL, in combination with the older World's Great Lakes, present an opportunity to explore evolution and adaptation of fish to oceanic type physical conditions.

Recruitment forecast models for walleye pollock Theragra chalcogramma fine-tuned from juvenile survey data, predator abundance and environmental phase shifts

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 417:237-248 (2010) - DOI: https://doi.org/10.3354/meps08817 Recruitment forecast models for walleye pollock Theragra chalcogramma fine-tuned from juvenile survey data, predator abundance and environmental phase shifts Tianyang Zhang1, Kevin M. Bailey2, Kung-sik Chan1,* 1Department of Statistics and Actuarial Science, University of Iowa, 263 Schaeffer Hall, Iowa City, Iowa 52242, USA 2Alaska Fisheries Science Center, National Marine Fisheries Service, NOAA, 7600 Sand Point Way NE, Seattle, Washington 98115, USA *Corresponding author. Email: kchan@stat.uiowa.edu ABSTRACT: Forecasting recruitment of marine fishes from environmental effects acting upon larvae has proven difficult due to multiple, nonlinear, interacting factors influencing larval survival. We used another approach, which circumvents the period of high egg and larval mortality, and instead improves forecasts from juvenile abundance indices. We compared several statistical recruitment forecast models and demonstrate that an increasing abundance of predators on juvenile walleye pollock Theragra chalcogramma, particularly the arrowtooth flounder Atheresthes stomias, which now dominates the groundfish biomass in the Gulf of Alaska, and autocorrelation caused by intercohort interactions strongly affect pollock recruitment during the juvenile phase. Furthermore, the weight of predictor variables changes with threshold criteria, which are linked to phase shifts in the marine environment. Our results indicate that forecasting recruitment of marine fishes can be improved by considering factors that influence survival after the juvenile period, but also needs to account for changes in community structure and phase shifts in the environment, as opposed to only environmental correlates. Inclusion of these factors is consonant with biological knowledge of the species. KEY WORDS: Population dynamics · Fisheries · Environment · Ocean research · Regime shift · Ecological community · Fish recruitment · Forecast Full text in pdf format PreviousNextCite this article as: Zhang T, Bailey KM, Chan Ks (2010) Recruitment forecast models for walleye pollock Theragra chalcogramma fine-tuned from juvenile survey data, predator abundance and environmental phase shifts. Mar Ecol Prog Ser 417:237-248. https://doi.org/10.3354/meps08817 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 417. Online publication date: November 04, 2010 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2010 Inter-Research.

Spawning stock and recruitment in North Sea cod shaped by food and climate

In order to provide better fisheries management and conservation decisions, there is a need to discern the underlying relationship between the spawning stock and recruitment of marine fishes, a relationship which is influenced by the environmental conditions. Here, we demonstrate how the environmental conditions (temperature and the food availability for fish larvae) influence the stock–recruitment relationship and indeed what kind of stock–recruitment relationship we might see under different environmental conditions. Using unique zooplankton data from the Continuous Plankton Recorder, we find that food availability (i.e. zooplankton) in essence determines which model applies for the once large North Sea cod (Gadus morhua) stock. Further, we show that recruitment is strengthened during cold years and weakened during warm years. Our combined model explained 45 per cent of the total variance in cod recruitment, while the traditional Ricker and Beverton–Holt models only explained about 10 per cent. Specifically, our approach predicts that a full recovery of the North Sea cod stock might not be expected until the environment becomes more favourable.

Larval growth, size, stage duration and recruitment success of a temperate reef fish

Understanding the causes of variation in recruitment of marine fishes has been a central goal for marine ecologists, fishery scientists and resource managers over the last century. Although the idea that recruitment variability is linked to the pelagic environmental conditions that enhance larval growth, survival, and/or delivery is consensual, such relationship is poorly known for most species. In this study we analyzed patterns of recruitment and early life history of a temperate reef fish, Coris julis from the Azores archipelago to test the relationships between early life history and recruitment success over two consecutive years. Growth from hatch to larval age 30 d was the best predictor of recruitment, implying that fast growing larger-at-age larvae have a survival advantage and contribute more to high recruitment, supporting the “bigger-is-better” hypothesis. The “stage-duration” hypothesis and the predictions regarding the relationships between size at age (SAA), size at settlement (SAS) and recruit abundance were also partially supported. The results presented in this study highlight the importance of understanding the early life traits that determine recruitment and larval-survivorship patterns, especially early larval growth, as this may provide a basis for prediction of recruitment and thus management of resources.

A numerical study of inferred rockfish (Sebastes spp.) larval dispersal along the central California coast

AbstractSuccessful recruitment of marine fishes depends on survival during early life‐history stages, which is influenced by oceanic advection due to its impact on coastal trophodynamics and transport processes. Here we evaluate the influence of ocean circulation on the dispersal of rockfish (Sebastes spp.) larvae along the central California coast using an implementation of the Regional Ocean Modeling System, driven at the surface by output from the Coupled Ocean Atmosphere Mesoscale Prediction System. Thousands of floats simulating rockfish larval propagules, constrained to follow fixed depths, were released over a broad coastal area at 2‐day intervals, and transported by simulated ocean currents at depths of 1, 7, 20, 40, and 70 m. Trajectory statistics are averaged across the 4‐yr period from January 2000 through December 2003 to reveal mean trajectory direction, net displacement, fractional cross‐shore loss, and duration of retention for different seasons. On average, near‐surface propagules originating nearshore are transported offshore during the upwelling season, whereas deeper propagules move alongshore to the north. This vertical shear vanishes during winter, with most floats moving alongshore to the north, regardless of depth. After 35 days in the water column, typical transport distances were ∼50 km for floats remaining nearshore and ∼150 km for floats over the midshelf and slope. Implications for performance of marine reserves for rockfish conservation are discussed. Our results also provide evidence for a strong semiannual pattern of coastal retention rates, with high export of near‐surface drifters during the upwelling season. In contrast, high rates of shelf retention occurred for releases at 20 m and deeper during summer, and at all depths during winter.

Transport-determined early growth and development of jack mackerel Trachurus japonicus juveniles immigrating into Sagami Bay, Japan

Oceanographic conditions and transport processes are often critical factors that affect the early growth, survival and recruitment of marine fishes. Sagittal otoliths were analysed to determine age and early growth for 381 jack mackerel (Trachurus japonicus) juveniles from Sagami Bay on the Pacific coast of Japan. Two separate hatching periods (December and February–March) were identified. They originated from the spawning grounds in the East China Sea. Early growth and developmental rates of December-hatching fish were lower than those for February–March-hatching fish. It is likely that these differences were determined in the Kuroshio Current during transport from the spawning grounds to Sagami Bay, and the lower December water temperatures in the bay. Origin and hatch dates of juveniles in Sagami Bay were in contrast to previous research on Fukawa Bay, where April-or-later-hatching fish from spawning grounds in the coastal waters of southern Japan constituted about half of the juvenile population. Management of these two jack mackerel stocks needs to consider these differences in hatch date composition and spawning origins, as these differences could affect early growth and subsequent mortality.

Ontogenetic and seasonal trends in recent growth rates of Atlantic cod and haddock larvae on Georges Bank: effects of photoperiod and temperature

Growth rate is a key demographic factor affecting survival and recruitment of marine fishes. Yet in the field, the patterns of change in growth rate with development and the effects of environmental variability on growth are poorly understood. We examined several factors that may contribute to the observed variability in recent (i.e. 2 to 4 d before sampling) growth and survival of Atlantic cod Gadus morhua and haddock Melanogrammus aeglefinus larvae on the southern flank of Georges Bank for the years 1995 through 1999. For both species, strong ontogenetic and seasonal trends in larval growth rates were apparent. A rapid initial increase in specific growth rate with lar- val size was observed in both species, followed by a stanza with little change in specific growth rate and finally a gradual increase with size to a maximum specific growth rate. For larva of any given size, growth rate increased as the season progressed. A variety of models were used to explore and describe the relations among growth rate, larval size, photoperiod, temperature and other variables. Generalized additive models (GAMs) with both larval size (protein content) and photoperiod terms explained 48% and 61% of the variability observed in recent growth of cod and haddock, respec- tively. Residuals from these models were used to examine the effects of other factors on estimated growth rates. Salinity, water density (sigma-t, σt), distance along the Bank, bottom depth, tempera- ture (T) and residual T (observed T minus the long-term mean for a given day of the year) explained small but significant portions of the residual variability in larval growth rates. These data and other considerations suggest that, while both increasing photoperiod and temperature contribute to the increase in larval growth rates observed each spring, photoperiod rather than temperature was the better proxy for the seasonal trend in larval growth rates between March and May on Georges Bank. Feeding conditions and growth of larval Atlantic cod and haddock were poor during the late winter and spring of 1995 compared with those from 1997 to 1999.

Larval growth predicts the recruitment success of a coral reef fish.

While growth rates of pelagic larvae have been argued to be one of the principal determinants of the recruitment success of temperate marine fishes, it is not known if this is the case in the tropics. Here, we use larval growth histories derived from otoliths of a Caribbean reef fish to show that monthly variation in the intensity of settlement and recruitment of pelagic juveniles onto reefs is positively correlated with variation in growth rates 1-2weeks after larvae begin feeding. Our results suggest that the processes thought to underlie recruitment of marine fishes in temperate regions may also operate in the tropics and contrasts with current research on the causes of recruitment variability in coral reef fishes, which emphasises the role of larval transport.

Stock, recruitment and moderating processes in flatfish

A difficulty that frequently arises when stock-recruitment relationships are fitted to historical data of fish populations is the high degree of variation in recruitment so that the relationship is difficult to identify with any precision. The purpose of this paper is to describe refinements that can be made to the model by incorporating information on parallel environmental factors that also affect recruitment. The identification of the stock-recruitment relationship can be made with greater precision because of the reduction in the unexplained variability. Many investigations on the effects of environmental changes on recruitment have been published in the fisheries literature. It is, however, comparatively rare for the simultaneous effects on recruitment of environmental factors and stock size to be analysed. Here we describe the formulation of an appropriate mathematical relationship to describe these effects. The framework of this formulation is F.E.J. Fry's classification of environmental factors into one of five kinds: controlling, limiting, lethal, masking and directive, following the work of Neill et al. (1994) [Neill, W.H., Miller, J.M., Van der Veer, H.W, Winemuller, K.D., 1994. Ecophysiology of marine fish recruitment: a conceptual framework for understanding interannual variability. Neth. J. Sea Res. 32, 135–152.]. An examination of some of the theory underpinning stock-recruitment relationships indicates how independent experimental evidence on the effects of environmental factors on recruitment can be incorporated into the relationship in an appropriate mathematical form. A method is described for the graphical illustration of the relationship between, on the one hand, stock and recruitment allowing for the effects of environmental factors and, on the other hand, the relationship between environmental factors and recruitment allowing for changes in stock levels. The method is based on the idea of partial residuals (or adjusted variables) derived from statistical regression methodology. The scatter of the adjusted variables around the fitted relationship is often considerably less than that of the raw data. The method is illustrated by two examples of flatfish stocks, plaice ( Pleuronectes platessa) in the North Sea and English sole ( Pleuronectes vetulus) in the Hecate Strait off the coast of British Columbia.

Webs and scales: Physical and ecological processes in marine fish recruitment

Webs and scales: Physical and ecological processes in marine fish recruitment

Ecophysiology of marine fish recruitment: A conceptual framework for understanding interannual variability

Present data and our application of logic do not permit confident rejection of the null hypothesis: Interannual variation in recruitment of marine fishes (typified by certain flatfishes) is independent of ecophysiological factors. Our inability to reject this hypothesis reflects not its likely validity, but rather a lack of conceptual structure and appropriate data for realistic evaluation of alternative hypotheses. Therefore, in this paper, we set aside as presently intractable the problem of understanding in any generalizable way the specific effects of environment on interannual variation in marine fish recruitment. Instead, we return to a conceptual scheme first proposed almost 50 years ago by F.E.J. Fry for considering effects of environmental factors on the physiology of fishes. We first extend this scheme to population-level responses, including recruitment, and then even further, to community/ecosystem-level responses. Fry supposed that all of environment can be resolved into five classes of physiological effects—controlling (which set the pace of metabolism), limiting (which constrain maximum metabolism), lethal (which completely interdict metabolism), masking (which increase obligatory metabolic work), and directive (which release and unload metabolism by guiding enviroregulatory responses). We suggest that corresponding effects can be recognized at the levels both of population and community/ecosystem. The key analogy is that environment operates on individuals through metabolism, on populations through recruitment, and on communities/ecosystems through abiotic and biotic diversification. In the context of marine-fish populations, we propose that scope for population increase is the difference between maximum and maintenance recruitment to the spawning stock. Maintenance recruitment is the product of critical spawner density and spawner mortality rate; this product varies with environment as the resultant of controlling effects on the metabolism of individuals, and is increased by loading due to masking factors— e.g., predation—that increase one or both multiplicands. Maximum recruitment is limited by deficiencies of resources, primarily food, but also, potentially, by low spawner density. Population-level lethal factors cause extinction, by reducing population scope to sub-zero values for a time exceeding the generation interval. Directive factors distribute the population in space and time, influencing not only habitat use and zoogeographic range, but also providing context for genetic adaptation and speciation. Exploration of this conceptual scheme from the perspective of flatfish life-history strategies and population dynamics, leads to several testable ecophysiological hypotheses about recruitment.

M.M. Mullin Webs and scales. Physical and ecological processes in marine fish recruitment, xi, 135p. Washington Sea Grant Program, 1993. Price $25·00.

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Wind Speed and Mortality Rate of a Marine Fish, the Northern Anchovy ( Engraulis mordax )

Large variability in recruitment of marine fishes creates challenging management problems. In northern anchovy (Engraulis mordax), there is a significant linear relation between larval mortality rate and the frequency of calm, low wind speed periods during the spawning season, possibly because calm winds permit maintenance of concentrated patches of larval food. Neither cannibalism on larvae nor offshore transport contributed significantly to interannual variation in early larval mortality. These results are consistent with the hypothesis that wind-driven turbulent mixing affects variability in survival of young fish larvae. However, abundance of recruits does not necessarily reflect abundance of larvae surviving through this early stage.