Annual variation in habitat-specific recruitment success: implications from an individual-based model of Lake Michigan alewife (Alosa pseudoharengus) (original) (raw)
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Estuaries, 2003
The identification and protection of essential habitats for early life stages of fishes are necessary to sustain fish stocks. Essential fish habitat for early life stages may be defined as areas where fish densities, growth, survival, or production rates are relatively high. To identify critical habitats for young-of-year (YOY) alewives (Alosa pseudoharengus) in Lake Michigan, we integrated bioenergetics models with GIS (Geographic Information Systems) to generate spatially explicit estimates of potential population production (an index of habitat quality). These estimates were based upon YOY alewife bioenergetic growth rate potential and their salmonine predators' consumptive demand. We compared estimates of potential population production to YOY alewife yield (an index of habitat importance). Our analysis suggested that during 1994-1995, YOY alewife habitat quality and yield varied widely throughout Lake Michigan. Spatial patterns of alewife yield were not significantly correlated to habitat quality. Various mechanisms (e.g., predator migrations, lake circulation patterns, alternative strategies) may preclude YOY alewives from concentrating in areas of high habitat quality in Lake Michigan.
Species-specific preferences drive the differential effects of lake factors on fish production
Canadian Journal of Fisheries and Aquatic Sciences, 2020
As the global human population grows, it remains a top priority for communities, managers, policymakers, and stakeholders to maintain healthy, sustainable, and productive fisheries under continued global change. Here we used a dataset consisting of fish and lake characteristics for 536 lakes across Ontario, Canada, to test whether multiple climate, human, and biological factors differentially affect fish production (i.e., population biomass per hectare per year). We tested the hypothesis that temperature is the key driver of fisheries production by testing for the effects of multiple factors on the production of three top predatory fish species: cold-water lake trout (Salvelinus namaycush), cool-water walleye (Sander vitreus), and warm-water smallmouth bass (Micropterus dolomieu). Using boosted regression tree analyses, we found that lake trout production was most influenced by the volume of hypolimnetic habitat, walleye production was related to other climatic variables, and smallmouth bass production was most influenced by sampling day of the year followed by Secchi depth. Our results suggest that current fish production modelsthat only include temperature and body sizemay oversimplify important ecological complexities and thus misinform management decisions because species respond differently to environmental drivers. Résumé : Pour faire face à la croissance démographique mondiale, les communautés, gestionnaires, décideurs et parties prenantes doivent continuer de prioriser le maintien de ressources halieutiques saines, durables et productives dans un contexte de changements climatiques. Nous avons utilisé un ensemble de données constitué de caractéristiques de poissons et de lacs pour 536 lacs en Ontario (Canada) pour vérifier si divers facteurs climatiques, humains et biologiques exercent différents effets sur la production de poissons (c.-à-d. la biomasse de la population par hectare par année). Nous avons vérifié l'hypothèse voulant que la température soit le principal facteur qui module la production des pêches en examinant les effets de différents facteurs sur la production de trois espèces de prédateurs de niveau trophique supérieur, à savoir le touladi (Salvelinus namaycush), une espèce d'eau froide, le doré jaune (Sander vitreus), une espèce d'eau fraîche, et l'achigan à petite bouche (Micropterus dolomieu), une espèce d'eau chaude. En utilisant des analyses par arbre de régression augmenté, nous constatons que le volume des habitats hypolimnétiques exerce la plus forte influence sur la production des touladis, que la production de dorés jaunes est associée à d'autres variables climatiques et que la date d'échantillonnage, suivie de la profondeur mesurée par le disque de Secchi, influencent le plus la production d'achigans à petite bouche. Nos résultats donnent à penser que les modèles de production de poissons actuels, qui n'intègrent que la température et la taille du corps, pourraient trop simplifier d'importantes complexités écologiques et ainsi produire des décisions de gestion non optimales découlant du fait que les espèces ne répondent pas toutes de la même manière à différents facteurs environnementaux. [Traduit par la Rédaction]
Canadian Journal of Fisheries and Aquatic Sciences, 2010
Factors affecting the early life survival of fishes are often difficult to demonstrate because variable immigration and mortality rates coupled with noncontinuous sampling may confound estimates of mortality and bias inference to more numerous smaller individuals. The larval production estimate (LPE) method eliminates these problems by compensating catch data for size-or age-specific mortality and growth and back-calculating abundance at a predetermined size or age. Despite its utility, LPE has not been widely applied in studies of freshwater fish recruitment. We executed an LPE analysis using 10-14 mm and 15-19 mm size classes of Upper Klamath Lake's (UKL) endangered Lost River suckers (Deltistes luxatus) and shortnose suckers (Chasmistes brevirostris) for five cohorts per year for 1995-2001. Larval survival peaked when habitat conditions included high availability of emergent macrophytes as habitat (>15 000 m 3 ), air temperatures between 14 and 22 8C, and a low frequency of wind speeds >16 kmÁh -1 . Age-0 juvenile suckers collected later in each year corroborated results of the LPE analysis, as most (88%) juveniles had otolith-estimated swim-up dates corresponding to early life rearing under the specified habitat conditions. Our results support the management practice of maintaining higher than natural UKL water surface elevations through the larval rearing period.
Ecological Modelling, 2020
Over the last two decades, major changes in abundance and population characteristics of Alewife (Alosa pseudoharengus), an anadromous herring species, have been observed along the US Atlantic coast. Loss of spawning habitat, bycatch mortality in the directed pelagic fisheries, increased predation mortality by rebounding predators such as Striped Bass, changes in water flow and temperature affecting recruitment success, changes in ocean thermal habitat and direct and indirect effects of changes in zooplankton community have been expounded by different researchers as putative hypotheses for population changes in Alewife. Unfortunately, longterm, concurrently-measured time series of regional factors and direct measures of biological processes needed to elucidate underlying causes are severely lacking for Alewife. Therefore, we developed, calibrated and validated a mechanistic, spatially-explicit, full life-cycle simulation model that can be used to explore population responses of Alewife to various exogeneous drivers. Daily processes such as spawning, recruitment, mortality, exploitation, predation and movements are generated by using empirically-derived deterministic and stochastic relationships and time-series of environmental data linked to specific life stages. We demonstrate the use of the model as an investigative tool by simulating three hypotheses and comparing model results to observed trends in Alewife populations from southern New England.
Recruitment Variability of Alewives in Lake Michigan
Transactions of the American Fisheries Society, 2005
We used a long-term series of observations on alewife Alosa pseudoharengus abundance that was based on fall bottom-trawl catches to assess the importance of various abiotic and biotic factors on alewife recruitment in Lake Michigan during 1962-2002. We first fit a basic Ricker spawner-recruit model to the lakewide biomass estimates of age-3 recruits and the corresponding spawning stock size; we then fit models for all possible combinations of the following four external variables added to the basic model: an index of salmonine predation on an alewife year-class, an index for the spring-summer water temperatures experienced by alewives during their first year in the lake, an index of the severity of the first winter experienced by alewives in the lake, and an index of lake productivity during an alewife year-class's second year in the lake. Based on an information criterion, the best model for alewife recruitment included indices of salmonine predation and spring-summer water temperatures as external variables. Our analysis corroborated the contention that a decline in alewife abundance during the 1970s and early 1980s in Lake Michigan was driven by salmonine predation. Furthermore, our findings indicated that the extraordinarily warm water temperatures during the spring and summer of 1998 probably led to a moderately high recruitment of age-3 alewives in 2001, despite abundant salmonines.
Canadian Journal of Fisheries and Aquatic Sciences, 2001
We investigate whether a process-oriented approach based on the results of field, laboratory, and modelling studies can be used to develop a stock-environment-recruitment model for Central Baltic cod (Gadus morhua). Based on exploratory statistical analysis, significant variables influencing survival of early life stages and varying systematically among spawning sites were incorporated into stock-recruitment models, first for major cod spawning sites and then combined for the entire Central Baltic. Variables identified included potential egg production by the spawning stock, abiotic conditions affecting survival of eggs, predation by clupeids on eggs, larval transport, and cannibalism. Results showed that recruitment in the most important spawning area, the Bornholm Basin, during 1976-1995 was related to egg production; however, other factors affecting survival of the eggs (oxygen conditions, predation) were also significant and when incorporated explained 69% of the variation in 0-group recruitment. In other spawning areas, variable hydrographic conditions did not allow for regular successful egg development. Hence, relatively simple models proved sufficient to predict recruitment of 0-group cod in these areas, suggesting that key biotic and abiotic processes can be successfully incorporated into recruitment models.
Canadian Journal of Fisheries and Aquatic Sciences, 2006
Long-term population trends are generally explained by factors extrinsic (e.g., climate, predation) rather than intrinsic (e.g., genetics, maternal effects) to the population. We sought to understand the long-term population dynamics of an important native Lake Michigan prey fish, the bloater Coregonus hoyi. Over a 38-year time series, three 10-to 15-year phases occurred (poor, excellent, and then poor recruitment) without high interannual variability within a particular phase. We used dynamic linear models to determine whether extrinsic (winter and spring temperature, alewife predator densities) or intrinsic factors (population egg production, adult condition, adult sex ratio) explained variation in recruitment. Models that included population egg production, sex ratio, winter and spring temperature, and adult bloater condition explained the most variation. Of these variables, sex ratio, which ranged from 47% to 97% female across the time series, consistently had the greatest effect: recruitment declined with female predominance. Including biomass of adult alewife predators in the models did not explain additional variation. Overall our results indicated that bloater recruitment is linked to its sex ratio, but understanding the underlying mechanisms will require additional efforts.
Canadian Journal of Fisheries and Aquatic Sciences, 2012
For Gulf of Alaska (GOA) fish populations, ordination by principal component analysis of a matrix of species by early life history and ecological traits resulted in distribution of species along three primary gradients. These are synonymous with phenology of egg and larval production, quantity of production, and ubiquity of larvae, the latter representing temporal and spatial extent of distribution in the pelagic environment. GOA species were assigned to categories that shared similar positions in ordination space relative to the three primary gradients. From this comparative analysis, a conceptual framework is proposed for species' early life histories representing trade-offs in adaptation to prevailing environmental conditions and associated vulnerability and resilience factors that may modulate species' recruitment responses to environmental variability. The utility of this framework for evaluating response to environmental forcing was supported by the analysis of a 27-year time series of GOA late spring larval fish abundance. The hypothesis for this ongoing research is that we can utilize similarities in reproductive and early life history characteristics among species to identify (i) ecologically determined species groups that are predisposed to respond to environmental forcing in similar ways and (ii) plausible environmental predictors of recruitment variation attributable to aspects of early life history.
Canadian Journal of Fisheries and Aquatic Sciences, 2010
Spatial management of marine populations typically requires consideration of larval dispersal pathways. When a power plant with a cooling water intake system (CWIS) is present, managers must also account for reductions in larval supply to natural habitats due to larval entrainment in the CWIS. To evaluate the consequences of CWIS entrainment for benthic populations, we coupled a transport model for an idealized coastline to a spatially explicit metapopulation model. CWIS entrainment reduced the probability of dispersal to and from sites near the CWIS. However, the reductions in larval supply due to entrainment generally produced only minor, localized effects on adult population density because of postsettlement density-dependent mortality. Only when population densities were already reduced by other forms of adult or larval mortality did entrainment threaten population persistence. Our simulations suggest that subpopulations several kilometres upstream of CWIS make the greatest contribution to metapopulation persistence by countering the effects of CWIS entrainment, and these locations should be the focus of conservation efforts to enhance larval sources. Finally, we show that traditional statistics used to estimate the demographic effects of CWIS entrainment are generally inaccurate and unreliable because they ignore nonlinearities in population dynamics.
Canadian Journal of Fisheries and Aquatic Sciences, 2006
The dreissenid mussel invasion of Lake Michigan during the 1990s has been linked to a concomitant decrease in the abundance of the amphipod Diporeia. We tracked the seasonal energy dynamics of alewife (Alosa pseudoharengus) in Lake Michigan during 2002-2004 and compared our findings with previously published results for years [1979][1980][1981]. Adult alewife energy density exhibited a pronounced seasonal cycle during both the pre-invasion and post-invasion periods, with energy density in October or November nearly twice as high as that in early summer. However, on average, adult alewife energy density was 23% lower during the post-invasion period compared with the preinvasion period. This significant decline in energy density was attributable to decreased importance of Diporeia in adult alewife diet. In contrast, energy density of juvenile alewives did not significantly differ between the pre-invasion and post-invasion periods. To attain a weight of 8 kg by age 4, bioenergetics modeling indicated that a Chinook salmon (Oncorhynchus tshawytscha) in Lake Michigan would have to consume 22.1% more alewives during the post-invasion period compared with the pre-invasion period.