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1.
Understanding the environmental factors that regulate fish recruitment is essential for effective management of fisheries. Generally, first‐year survival, and therefore recruitment, is inherently less consistent in systems with high intra‐ and interannual variability. Irrigation reservoirs display sporadic patterns of annual drawdown, which can pose a substantial challenge to recruitment of fishes. We developed species‐specific models using an 18‐year data set compiled from state and federal agencies to investigate variables that regulate the recruitment of walleye Sander vitreus and white bass Morone chrysops in irrigation reservoirs in south‐west Nebraska, USA. The candidate model set for walleye included only abiotic variables (water‐level elevation, minimum daily air temperature during winter prior to hatching, annual precipitation, spring warming rate and May reservoir discharge), and the candidate model set for white bass included primarily biotic variables (catch per unit effort (CPUE) of black crappie Pomoxis nigromaculatus, CPUE of age‐0 walleye, CPUE of bluegill Lepomis macrochirus and CPUE of age‐3 and older white bass), each of which had a greater relative importance than the single abiotic variable (minimum daily air temperature during winter after hatching). Our findings improve the understanding of the recruitment of fishes in irrigation reservoirs and the relative roles of abiotic and biotic factors.  相似文献   

2.
High rates of unexplained mortalities (up to 70%) are anticipated in the cultured juvenile sea bass (Dicentrarchus labrax) in farms in the eastern Black Sea at least for the last 8 years. Diplectanum aequans, often blamed for the observed mortalities, is the only prevalent parasite impacting the health of sea bass in the brackish water of the Black Sea. To investigate the seasonal fluctuation of D. aequans prevalence, mean intensities and the potential effects of D. aequans on the fitness of sea bass, eight cages from one farm (Farm A) and four cages at another distinct site (Farm B) were surveyed monthly from May to October of 2008. Six hundred and sixty‐one juvenile sea bass from Farm A and 236 from Farm B were individually examined for the presence and intensity of the parasite. The prevalence of D. aequans in cultured sea bass (96.3 ± 11.11; Mean ± SD) ranged from 66.7% to 100% in June, the beginning of 6‐month growing season. The mean intensity was 6.08 ± 2.19, significantly higher than that (2.74 ± 0.87; P < 0.05) in December (P < 0.05), the end of the growing season. Fish with low fitness had significantly higher number of parasite than the fish with higher fitness (P < 0.005). Although D. aequans negatively influenced host's condition factor, the impact was not enough to lead mortalities in the cultured sea bass in the Black Sea.  相似文献   

3.
Drift of propagules occurs within many populations inhabiting flow fields. This affects the number of propagules that rejoin their source population (recruitment) and plays a role in adaptive spatial redistribution. We focus on the cause and consequence of interannual variation in geographic distribution of population density among five cohorts of young‐of‐the‐year (age‐0) juvenile walleye pollock Gadus chalcogrammus in the western Gulf of Alaska (GOA). The coastal GOA is a wind‐driven advective system. Walleye pollock spawn during spring and their eggs and larvae drift southwestward; by late summer, age‐0 juveniles are variously distributed over the shelf. We found that high population densities of age‐0 juveniles (ca. 6 months old) near the southwestward exit of the Alaska Coastal Current from the GOA corresponded with high abundance of larvae from the major spawning area upstream, but did not translate into high abundance at older ages. Further, offshore and upwelling‐favorable winds were associated with the high downstream abundance and presumed export. In contrast, downwelling‐favorable (northeasterly) wind during and shortly after spawning (April–May) was associated with high recruitment at age 1. Finally, we found that recruitment also increased with apparent retention of age‐0 juveniles in favorable habitat upstream near the main spawning area. We hypothesize that wind‐related retention in superior upstream habitat favors recruitment. Our results argue for including wind‐driven transport in future walleye pollock recruitment models. We encourage more work on the juvenile stage of marine fishes aimed at understanding how transport and species‐specific habitat suitability interact to affect population response to large‐scale forcing.  相似文献   

4.
Alabama bass, Micropterus henshalli Hubbs & Bailey, are the dominant sportfish of Allatoona Reservoir, Georgia, USA, but no population assessment has been conducted. Thus, growth and total annual mortality were estimated in spring 2005, and a tagging study was conducted in 2006 and 2007 to estimate angler exploitation. These data were used with an age‐structured model to assess performance of a 356‐mm minimum length limit (MLL), a 406‐mm MLL and a 330‐ to 406‐mm protected slot length limit (SLL) compared to the present harvest regulation of no MLL. Mean annual exploitation varied from 12 to 22% each year and was generally highest for fish > 330 mm; total annual mortality was 44%. Models predicted a 49–153% increase in numbers of Alabama bass reaching 432 mm, a 22–66% decline in numbers harvested and only moderate declines in yield (5–25%) with the alternative harvest regulations compared to current conditions. The SLL may be an acceptable compromise to allow Allatoona Reservoir anglers to still harvest fish while also improving Alabama bass size structure.  相似文献   

5.
Imperfect detection can present a significant challenge when monitoring for a rare and imperilled species. Here, a long‐term larval and early‐juvenile fish monitoring programme in the upper San Francisco Estuary was examined to evaluate its overall reliability in detecting various fish species, including the imperilled delta smelt, Hypomesus transpacificus McAllister, for which the programme was designed. Using occupancy modelling, detection probability of species with pelagic larval or juvenile life stages was found to be generally high (≥.95) based on the current sampling effort of three larval net tows per site. However, detection probability can vary considerably from year to year depending on the species’ level of larval production. Water temperature and turbidity were identified as important predictors of occurrence for young‐of‐year delta smelt, longfin smelt Spirinchus thaleichthys (Ayres) and striped bass Morone saxatilis (Walbaum), and there was evidence for fish size selectivity by the sampling gear in all three species. These results highlight the need to consider adaptively managing detection probability by increasing sampling effort in years when young‐of‐year delta smelt abundance is expected to be low, especially when information on the species’ occurrence at a particular region is critical.  相似文献   

6.
A series of experiments were conducted to obtain an efficient larval rearing protocol for Megabalanus azoricus. The first part of this study investigates the effect of microalgae‐based diets on survival and larval development. Mono and mixed‐diets were tested at 20 ± 1°C, in a sequence of 11‐day feeding experiments. The second part presents a preliminary study on the influence of a biofilm on recruitment and use of oyster spat collectors in a mass rearing system. A photographic record of larval development and a brief reference to the diagnostic features that enable quick larval staging are also presented, along with morphometric measurements. Of the microalgae tested (Chaetoceros sp., Chloromonas sp., Dunaliella sp., T‐Isochrysis sp. and Skeletonema sp.) the mixed‐diet Skeletonema sp. with T‐Isocrysis sp. showed the highest survival percentages: total survival ranged from 79.7 to 85.7% and 69.7–80.0% of nauplii were in stage VI after 11 days of rearing. Cypris were also present, but only represented 5.3% of the survivors at most. In the mass rearing system juveniles were found settled in the collectors after 25 days, at 20 ± 1°C. However recruitment was less than 1%. Preliminary results showed no settlement preference towards collectors with biofilm. Nevertheless, this study provides the first record of M. azoricus settlement under laboratorial conditions and represent a starting point for future larval rearing studies.  相似文献   

7.
This study compared the growth of sea urchin Paracentrotus lividus larvae cultured using two different rearing methods: a variable method based on a variable amount of feed (microalgae) and seawater exchange (30% or 50%) established according to the phytoplankton concentration in the larval cultures and a fixed method characterized by a fixed amount of feed and seawater exchange. Three microalgae diets, Isochrysis sp. (Tahitian strain, T‐Iso), Chaetoceros gracilis and a 50:50 mixed diet, were tested with both rearing methods. Larval development and survival were assessed at the 6‐arm pluteus stage (P6), competence (Cp) and metamorphosis (Mt). Data showed that the variable method reduced the requirements for phytoplankton and seawater exchange. Indeed, through the optimization of feed rations, it was possible to reduce the production of debris and settled phytoplankton, minimizing the need for water exchanges. Higher larval survival resulted at Cp and Mt stages for those reared with the variable method as opposed to the fixed one. Survival and development were also influenced by the tested dietary treatments: at Mt stage, the mixed diet resulted in a higher larval survival (63.3 ± 8.9%) than T‐Iso (19.7 ± 12.1%) and C. gracilis (23.4 ± 15.1%) (P < 0.05). These results suggest that the use of the variable method improves the larval survival and development and also it reduces resource consumption (phytoplankton, seawater use and work effort), which in turn could potentially improve the hatchery production of P. lividus.  相似文献   

8.
The present study evaluates the effect of two temperatures, 14°C (T14) and 18°C (T18), on yield and the presence of cranial abnormalities during early development in north palm ruff (Seriolella violacea). Different time indices – days post‐hatching (DPH), degree‐days (D°) and effective degree‐days (D°eff) – were used to analyse growth during cultivation. Several ontogenetic events were achieved in less time during cultivation at 18°C. Additionally, a larger total length and final weight, as well as a higher survival rate, were achieved after 80 days of culture at higher temperatures (T18 = 55.5 ± 1.5 mm; 2.87 ± 0.21 g; 1.80 ± 0.18% and T14 = 24.3 ± 2.2 mm; 0.26 ± 0.08 g; 1.33 ± 0.12%). D° and D°eff were valid as independent temperature indices for predicting the growth response of S. violacea against thermal variations. The frequencies of cranial skeletal abnormalities (mouth and opercular complex) were evaluated in the pre‐flexion, flexion, post‐flexion and juvenile stages. However, the frequency of cranial skeletal abnormalities at the end of this study was not significantly influenced (P > 0.05) by temperature, and values below 21% were recorded in both treatments. These results can be of practical use for optimizing culture conditions to maximize the yield and quality of S. violacea juveniles.  相似文献   

9.
Understanding spatial patterns in population characteristics and the principal natal environments supporting riverine fish populations are important for fisheries management. Fin ray microchemistry was used to identify natal environment, and age estimates from sectioned fin rays were used to estimate growth and mortality rates for spotted bass, Micropterus punctulatus (Rafinesque), in a segment of the Ohio River (Smithland Pool) and three tributaries. Differences in water Sr:Ca and Ba:Ca among the Ohio River and tributaries were reflected in fin ray edge Sr:Ca and Ba:Ca. Fourteen percent of spotted bass ≥ age 2 captured in the Ohio River originated in tributaries, whereas 10% captured in tributaries originated in the Ohio River. Spotted bass in the Ohio River reached larger maximum size (L∞ = 448.7) than conspecifics in tributaries (L∞ = 324.4), although mortality rates were not different. Although 86% of spotted bass were collected in their inferred natal environment, small tributaries may be a supplemental source of recruitment for the spotted bass stock in Smithland Pool.  相似文献   

10.
Processes influencing fish recruitment are often highly complex and inherently difficult to understand. Invasive species may complicate recruitment through habitat and food web modifications resulting in competitive bottlenecks. Common carp Cyprinus carpio have been distributed worldwide, and their introductions have resulted in destructive effects on aquatic ecosystems and food web dynamics. Common carp are highly fecund, and high densities of age‐0 carp may occur in some years that may reduce invertebrate prey resources and adversely affect native age‐0 fishes. We used enclosures and field observations to examine potential effects of age‐0 common carp on growth and survival of age‐0 yellow perch Perca flavescens and bluegill Lepomis macrochirus. Yellow perch and bluegill were stocked into enclosures with and without common carp (31 fish/m3) using a substitution experimental design, and fish growth and survival and invertebrate prey resources were assessed. Common carp reduced growth of yellow perch but not bluegill and did not affect survival of either species in mesocosms. Next, we used patterns of common carp, bluegill, and yellow perch abundance and total length across 38 lake‐years to evaluate potential interspecific interactions in natural systems. Age‐0 common carp abundance was not negatively related to size or abundance of bluegill or yellow perch. However, adult common carp and age‐0 yellow perch abundance were inversely related, suggesting a potential competitive bottleneck. Thus, age‐0 common carp may suppress growth of yellow perch when prey is limited, but adult common carp may have larger effects than early life stages on native juvenile fishes.  相似文献   

11.
This paper investigates environmental drivers of U.S. West Coast petrale sole (Eopsetta jordani) recruitment as an initial step toward developing an environmental recruitment index that can inform the stock assessment in the absence of survey observations of age‐0 and age‐1 fish. First, a conceptual life history approach is used to generate life‐stage‐specific and spatio‐temporally specific mechanistic hypotheses regarding oceanographic variables that likely influence survival at each life stage. Seven life history stages are considered, from female spawner condition through benthic recruitment as observed in the Northwest Fisheries Science Center West Coast Groundfish Bottom Trawl Survey (age‐2 fish). The study area encompasses the region from 40 to 48°N in the California Current Ecosystem. Hypotheses are tested using output from a regional ocean reanalysis model outputs and model selection techniques. Four oceanographic variables explained 73% of the variation in recruitment not accounted for by estimates based exclusively on the spawning stock size. Recruitment deviations were (a) positively correlated with degree days during the female precondition period, (b) positively correlated with mixed‐layer depth during the egg stage, (c) negatively correlated with cross‐shelf transport during the larval stage, and (d) negatively correlated with cross‐shelf transport during the benthic juvenile stage. While multiple mechanisms likely affect petrale sole recruitment at different points during their life history, the strength of the relationship is promising for stock assessment and integrated ecosystem assessment applications.  相似文献   

12.
In order to understand better the recruitment variability in European anchovy in the Bay of Biscay, it is important to investigate the processes that affect survival during the early life stages. Anchovy juvenile growth trajectories and hatch‐date distributions were inferred over a 3‐year period based on otolith microstructure analysis. Otolith growth trajectories showed a characteristic shape depending on their hatch‐date timing. Earlier‐born juveniles had notably broader maximum increments than later born conspecifics, resulting in higher growth rates. This observation suggests that early hatching would be beneficial for larval and juvenile growth, and, therefore, survival. The estimated juvenile hatch‐date distributions were relatively narrow compared with the extended anchovy spawning season (March–August) in the Bay of Biscay and indicated that only individuals originated mainly from the summer months (June–August) survived until autumn. Hatch‐date distributions were markedly different among years and seemed to influence the interannual recruitment strength of anchovy. We conclude that years characterized by juvenile survivors originating from the peak spawning period (May and June) would lead to considerable recruitment success. Downwelling events during the peak spawning period seem to affect larval survival. Furthermore, size‐dependent overwinter mortality would be an additional process that regulates recruitment strength in the anchovy population in the Bay of Biscay.  相似文献   

13.
This study was performed to determine the effect of starvation and delayed feeding on activities of digestive enzymes and alkaline phosphatase (ALP) of larval red swamp crayfish (Procambarus clarkii), so as to reveal the tolerance to prolonged starvation and the recovery of digestive enzymes after delayed feeding in larval and juvenile P. clarkii. In the control group, activities of trypsin and ALP increased significantly (p < .05) with day‐age and then kept constant at 24 days after hatching (DAH) and 10 DAH, respectively, whereas the activities of amylase and pepsin increased firstly then decreased with day‐age, and the activity of lipase increased firstly then decreased and then increased again during the development period of juvenile P. clarkii (1–31 DAH). In the group with continuous starvation (CS), activities of pepsin and lipase both decreased (p < .05) after fasting, and the activities of pepsin, lipase and trypsin in the groups with delayed feeding all increased (p < .05) and recover to the levels of the control group after food supply. However, the activity of amylase increased (p < .05) in the CS group, and it decreased to normal level after food supply. The ALP activity did not significantly (p > .05) vary after starvation, whereas it decreased in the groups with delayed feeding after 1 day of food supply, and then increased back to the level similar with the control group. Results from this study could provide information for diet preparation and feeding regime in larval and juvenile red swamp crayfish culture.  相似文献   

14.
As adhesion and translocation through fish gut enterocytes of the pathogen Vibrio (Listonella) anguillarum are not well investigated, the effective cause of disease and mortality outbreaks in larval sea bass, Dicentrarchus labrax, suffering from vibriosis is unknown. We detected V. anguillarum within the gut of experimentally infected gnotobiotic sea bass larvae using transmission electron microscopy and immunogold labelling. Intact bacteria were observed in close contact with the apical brush border in the gut lumen. Enterocytes contained lysosomes positive for protein A‐gold particles suggesting intracellular elimination of bacterial fragments. Shed intestinal cells were regularly visualized in the gut lumen in late stages of exposure. Some of the luminal cells showed invagination and putative engulfment of bacterial structures by pseudopod‐like formations. The engulfed structures were positive for protein A‐colloidal gold indicating that these structures were V. anguillarum. Immunogold positive thread‐like structures secreted by V. anguillarum suggested the presence of outer membrane vesicles (MVs) hypothesizing that MVs are potent transporters of active virulence factors to sea bass gut cells suggestive for a substantial role in biofilm formation and pathogenesis. We put forward the hypothesis that MVs are important in the pathogenesis of V. anguillarum in sea bass larvae.  相似文献   

15.
The nematode Panagrolaimus sp. was tested as live feed to replace Artemia nauplii during first larval stages of whiteleg shrimp Litopenaeus vannamei. In Trial 1, shrimp larvae were fed one of four diets from Zoea 2 to Postlarva 1 (PL1): (A) Artemia nauplii, control treatment; (NC) nematodes enriched in docosahexaenoic acid (DHA) provided by the dinoflagellate Crypthecodinium cohnii; (N) non‐enriched nematodes; and (Algae) a mixture of microalgae supplemented in C. cohnii cells. In Trial 2, shrimp were fed (A), (NC) and a different treatment (NS) with nematodes enriched in polyunsaturated fatty acids (PUFAs) provided by the commercial product S.presso®, until Postlarva 6 (PL6). Mysis 1 larvae fed nematodes of the three dietary treatments were 300 μm longer (3.2 ± 0.3 mm) than control larvae. At PL1, control shrimp were 300 μm longer (4.5 ± 0.3 mm) than those fed DHA‐enriched or PUFAs‐enriched nematodes. No differences were observed in length and survival at PL6 between control larvae and those fed DHA‐enriched nematodes (5.1 ± 0.5 mm; 33.1%–44.4%). Shrimp fed microalgae showed a delay in development at PL1. This work is the first demonstration of Panagrolaimus sp. suitability as a complete substitute for Artemia in rearing shrimp from Zoea 2 to PL6.  相似文献   

16.
In this study, the embryonic and larval development stages of one of the most important ornamental fish serpae tetra (Hyphessobrycon eques) are described. The early life stage is documented from fertilization until the beginning of the juvenile period. The fertilized eggs (the average diameter = 938.55 ± 35.20 µm) were incubated at a water temperature of 26 ± 0.5°C. The cleavage finished in 1:10 hr (=h) and the early blastula stage occurred at 1:26 hr post fertilization (hpf). The gastrulation started at 3:05 hpf, and 50% epiboly was observed at 3:25 hpf. Segmentation stage was monitored at 7:26 hpf. Embryonic developmental stage was completed and hatching occurred 20–21 hpf. The total length (TL) of newly hatched larvae was 2.64 ± 0.21 mm. The larval development of serpae tetra was divided into four different periods: Yolk‐sac larva (1–4 DAH, TL = 2.77 ± 0.09 mm ‐ 3.85 ± 0.11 mm), preflexion larva (5–12 DAH), flexion larva (13–15 DAH, TL = 5.78 ± 0.46 mm on the 15th day) and post‐flexion larva (16–30 DAH, TL = 10.7 ± 0.27 mm on the 28th–30th days). The mouth and anus are closed at 1 DAH. The mouth and anus opened at 4 DAH. Exogenous feeding started on the 4th day. The first gulping of the swim bladder was on days 3. The larva begins to swim freely, and the yolk sac was completely consumed at 4 DAH. Histological structures of the eye and brain of new hatched larva were clearly identified at 1 day after hatching (DAH). According to histological findings, the digestive system (stomach, intestine) started to develop and the liver could be seen on the ventral side of the swim bladder at 5 DAH. No histological difference was observed between the anterior intestine and the posterior intestine at 15–16 DAH. The larval metamorphosis was completed, and the larvae transformed into juveniles at 28–30 DAH.  相似文献   

17.
A 25‐week immersion challenge was conducted exposing Oreochromis mossambicus, Oreochromis aureus and Oreochromis urolepis hornorum to Francisella noatunensis subsp. orientalis (Fno). Two populations were compared for each fish species; ‘resident fish’ were defined as fish maintained in tanks since week 0 of challenge, whereas ‘naïve fish’ were defined as fish added to tanks once temperature in water reached <26 °C at 21 weeks post‐challenge. Fno genome equivalents (GEs) in water were similar in all treatments 1 h post‐challenge; however, significantly lower Fno GEs were detected 2 weeks post‐challenge in all tanks, and the only treatment with detectable Fno GE after 4 weeks of challenge were the O. mossambicus tanks. Twenty‐one weeks post‐challenge, naïve fish were stocked with ‘resident’ cohorts. Over a 4‐week period, mortalities occurred consistently only in O. mossambicus naïve cohorts. Overall presence of granulomas in spleen of survivors was similar (>55%) in all resident populations; however, in naïve populations, only O. mossambicus presented granulomas. Similarly, only O. mossambicus presented viable Fno in the spleen of survivors, and Fno GEs were only detected in O. mossambicus, and in resident O. aureus. In conclusion, the results of this study suggest different susceptibility of tilapia species to piscine francisellosis.  相似文献   

18.
Data from stock assessment surveys, published research and climate sensors were linked to model the interaction between fishing, physical‐oceanographic processes and spatial patterns of larval settlement for western king prawn [Penaeus (Melicertus) latisulcatus]. This information was used to evaluate the trade‐off between larval recruitment and catch during fishing periods that demand high prices but coincide with spawning. Total rates of larval settlement were maximized when tidal currents and atmospheric physical‐forcing components were coupled with simulations of larval swimming behaviour under average gulf temperatures. Average gulf temperatures sustained longer larval durations and increased larval settlement rates by over 12% compared with warmer gulf conditions simulated under a scenario of global warming. Reproductive data coupled with outputs from the biophysical model identified consistent inter‐annual patterns in the areas contributing to larval settlement success. Areas located in the north‐east, and central‐west of the fishery, consistently contributed to over 40% of all larvae reaching a settlement in each year. Harvest sensitivity analyses indicated that changes in the spatial patterns of pre‐Christmas fishing could lead to improvements in overall rates of the larval settlement while maintaining or improving the levels of catch. Future studies to refine the model inputs relating to physical processes, larval behaviour and mortality rates for P. latisulcatus coupled with surveys of juvenile prawn abundance to ground truth the modelled predictions, would allow stock recruitment relationships to be more closely examined and inform adaptive management of the fishery in the future.  相似文献   

19.
Freshwater growth of juvenile sockeye salmon (Oncorhynchus nerka) depends upon the quality and quantity of prey and interactions with potential competitors in the foraging environment. To a large extent, knowledge about the ecology of lake‐rearing juvenile sockeye salmon has emerged from studies of commercially important runs returning to deep nursery lakes, yet information from shallow nursery lakes (mean depth ≤ 10 m) is limited. We examined seasonal and ontogenetic variation in diets of juvenile sockeye salmon (N = 219, 30–85 mm) and an abundant potential competitor, threespine stickleback (Gasterosteus aculeatus; N = 198, 42–67 mm), to understand their foraging ecology and potential trophic interactions in a shallow Alaska lake. This study revealed that adult insects made up 74% of all sockeye salmon diets by weight and were present in 98% of all stomachs in Afognak Lake during the summer of 2013. Diets varied temporally for all fishes, but small sockeye salmon (<60 mm) showed a distinct shift in consumption from zooplankton in early summer to adult insects in late summer. We found significant differences in diet composition between sockeye salmon and threespine stickleback and the origin of their prey indicated that they also separated their use of habitat on a fine scale; however, the two species showed overlap in size selectivity of zooplankton prey. Considering that aquatic insects can be a primary resource for juvenile sockeye salmon in Afognak Lake, we encourage the development of nursery lake carrying capacity models that include aquatic insects as a prey source for sockeye salmon.  相似文献   

20.
The identification of anthropogenic and environmental drivers on length‐at‐age of fish stocks is important to understanding ecosystem dynamics and harvest intensity. We evaluated coastwide annual growth of n = 187,115 Atlantic Menhaden (Brevoortia tyrannus) and n = 299,185 Gulf Menhaden (B. patronus), using samples collected from the North, Mid‐, and South Atlantic from 1961 to 2016 and across the Gulf of Mexico from 1977 to 2016. Using hierarchical models of age 1 growth and age 2 growth, we evaluated a suite of candidate predictors including fishery landings, easterly (U) and northerly (V) wind velocity, river discharge, juvenile abundance, and the Atlantic Multi‐decadal Oscillation (AMO). We found age 2 growth rates were smaller than age 1 growth rates for both species and that Atlantic Menhaden growth rates were 3–4 times greater than Gulf Menhaden. Age 1 growth rate of Atlantic Menhaden was positively affected by landings lagged by one year, indicating a density‐dependent mechanism. In addition, AMO (negative effect), and wind U (positive effect) and wind V (negative effect) in the North Atlantic region were significant factors influencing coastwide age 1 Menhaden growth. Wind V (negative effect) and AMO (positive effect) influenced age 1 Gulf Menhaden growth. No environmental factors were found to have an effect on age 2 Atlantic Menhaden growth, and AMO was the only significant predictor (weak negative effect) of age 2 Gulf Menhaden growth. Fishing pressure was the primary influence on age 1 Atlantic Menhaden growth, whereas age 1 Gulf Menhaden growth was primarily influenced by environmental conditions.  相似文献   

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