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1.
Measuring and forecasting recruitment are central to the understanding and management of fish stocks. Kainge et al. (2013) studied the effect of spawning stock size and environmental fluctuations on the recruitment levels of the Cape hake Merluccius capensis in Namibia. However, their study contains some flaws that undermine the conclusion that Cape hake recruitment is under the influence of upwelling in summer. Until those flaws are properly addressed, this conclusion, in our view, should be treated with caution.  相似文献   

2.
Short-lived species are extremely dependent on the seasonal and interannual variability of environmental conditions, and determining their stock status is often difficult. This study investigates the effects of environmental variability and fishing pressure on the stock of octopus Octopus vulgaris in Senegalese waters over a 10-year period from 1996 to 2005. Monthly catches-at-age were estimated based on catch-at-weight data and a polymodal decomposition constrained by a given growth curve. Octopus recruitments and fishing mortalities were then estimated using a catch-at-age analysis performed on a monthly basis. Yield and biomass per recruit were simulated using a Thompson and Bell model and used to generate a diagnostic of the fishery's impacts. Results indicate that the high interannual and seasonal variability of the octopus stock biomass is linked to the spring recruitment event, the annual intensity of which was significantly correlated with the coastal upwelling index and sea surface temperature. Yield per recruit varied seasonally but remained almost unchanged from one year to the next. Even when catches vary strongly according to recruitment, the octopus stock appears to be consistently fully exploited, or slightly overexploited in some years. In this context of environmental variability, usual indicators such as the maximum yield per recruit, and the related fishing mortality and spawning potential ratio, remain useful for fisheries management purposes.  相似文献   

3.
Seasonal and short-term variability of environmental parameters influence the spawning strategies of fish species. In this study, the spawning strategies and the transport of early stages of the two Cape hake species off South Africa were investigated. Distribution of eggs and larvae of Merluccius paradoxus and M. capensis was analysed in order to derive more detailed and species-specific information on spawning season, spawning location, and transport of early stages. Samples were collected during three pilot surveys between January and October 2007 and during an extensive survey in September/October 2008 in the southern Benguela upwelling system off South Africa. Eggs and larvae of M. paradoxus were found in greater numbers than those of M. capensis during all surveys. Highest abundances were found from September to October, indicating one spawning peak for M. paradoxus during late austral winter to spring. The western Agulhas Bank was identified as the primary spawning ground, and smaller spawning events occurred on the West Coast. Larvae of both species were mainly distributed in subsurface waters between 25 and 100 m. More than 50% of all larvae caught had a total length between 3 and 4 mm and size increased significantly with decreasing latitude. Merluccius capensis were found closer inshore than M. paradoxus, indicating that early stages of the two species followed separate drift routes. We assume that this distribution pattern most likely evolved from differences in spawning location and phenology. The spawning strategies of M. paradoxus and M. capensis are well adapted to a time-frame of optimal transport conditions favourable for larval survival in the highly variable environment of the southern Benguela upwelling system, but the peak spawning of the two species is separated in time and space.  相似文献   

4.
Cape hake in Namibian waters are demersal and mesopelagic spawners, spawning peaking offshore between 100 and 400 m deep, depending on local environmental conditions. The cross-shelf circulation, low-oxygen layers and mesoscale gyres are three important environmental factors influencing hake spawning behaviour and subsequent transport of the spawning products. Normally, hake spawn offshore near the bottom at depths of 150–400 m. However, during one cruise, spawning was concentrated below several subsurface mesoscale gyres, resulting in reduced dispersion of the eggs and larvae. When the low-oxygen layer above the bottom is pronounced, hake spawning has been observed close to the top of the layer at oxygen concentrations as low as 0.2–0.3 m? ??1. The relatively small size of the eggs and their high specific gravity make them ascend quite slowly from the spawning depths, 10–40 m per day. Consequently, hake eggs spawned deeper than 200 m hatch before they reach the upper mixed layer. The newly hatched larvae are relatively undeveloped, without functional eyes or mouth, and display little swimming activity during their first hours, but laboratory observations have revealed subsequent periods of downward swimming activity. Based on current field observations, on buoyancy measurements of eggs and larvae and on observed larval behaviour, it is concluded that hake eggs and larvae are transported onshore by features of the upwelling subsurface circulation that compensate for offshore movement of surface water. This may be the basic mechanism concentrating early juvenile hake nearshore. Spawning activity near the low-oxygen layer might be a behavioural adaptation to minimize egg predation, because few other species are expected to survive such low concentrations of oxygen.  相似文献   

5.
张畅  陈新军 《海洋学报》2019,41(2):99-106
澳洲鲐（Scomber australasicus）是西北太平洋重要的中上层经济鱼类，生命周期相对较短，资源量受补充量影响明显，了解澳洲鲐太平洋群系补充量状况对掌握其资源量及确保其可持续利用具有重要的意义。本文利用产卵场1（30°~32°N，130°~132°E）海表面温度（sea surface temperature，SST1）、产卵场2（34°~35°N，138°~141°E）海表面温度（SST2）、索饵场（35°~45°N，140°~160°E）海表面温度（SST3）、潮位差（tidal range，TR）、太平洋年代际涛动（Pacific decadal oscillation，PDO）和亲体量（spawning stock biomass，SSB）6个影响因子任意组合与补充量构建多个模型，运用贝叶斯模型平均法（Bayesian model averaging，BMA）分析各个环境因子对资源补充量的解释能力，并预测其补充量的变化。结果表明，SSB对补充量具有最长期且稳定的解释能力，其次是SST3，PDO、TR、SST2、SST1也对补充量模型具有一定的解释能力。SST3是环境因子中影响最大的因子，可能是由于补充群体在索饵场内生活时间较长，索饵场温度对仔鱼或鱼卵的生长存活有较大的影响。研究认为，基于BMA的组合预报综合考虑了各个模型的优势，优于单一模型，可用于澳洲鲐资源补充量的预测。  相似文献   

6.
The SE Pacific stock of Patagonian grenadier (Macruronus magellanicus) showed evidence of an abrupt reduction in recruitment after 2000. This drop exceeded expectations from changes in the spawning stock biomass (SSB), indicating a change in the stock-recruitment relationship (S-R). We evaluated whether variability in recruitment could be explained by concurrent changes in three environmental indices: sea-surface temperature anomaly (SSTA); southern oscillation index (SOI); and latitudinal position of the west wind drift bifurcation (WWDL). Continuous and discrete effects of these indices were tested as covariates in linear log-log and non-linear Ricker's S-R models. Discrete effects represented regime shifts detected in SSTA (1998), SOI (1998) and WWDL (1995). While SSTA was the only continuous variable found to be significant, the discrete 1998 regime shift supported the most informative model. The best Ricker's model considered a discrete intercept change in the same year: 1998. Although a spurious correlation between SSTA and S-R changes is possible, SSTA may be reflecting major physical or biological changes relevant to M. magellanicus juveniles in the SE Pacific.  相似文献   

7.
Stock collapses have occurred worldwide. The most frequently cited cause is over-fishing, suggesting that fisheries management has been ineffective in controlling exploitation rates. The progression of a fishery from an over-exploited to a collapsed state involves impairment of the reproductive capacity of the target species, i.e. recruitment over-fishing. In many cases, this occurs by reduction of the spawning stock biomass (SSB) through the systematic elimination of spawning components within a stock complex. While operational definitions of minimum levels of SSB have been developed, they have seldom been applied and never adopted in a Canadian groundfish management context. The answer to the question of how much is enough to perpetuate a stock under exploitation has been illusive. Serebryakov [J. Cons. Int. Explor. Mer, 47 (1990) 267] has advocated definition of critical levels of SSB based on survival rates (R/SSB). We review his method and discuss the utility of the approach. An alternative approach to the problem of estimating minimum SSB is through a fundamental revision of the traditional stock and recruitment relationship. Explicit theoretical SSB thresholds below which reproduction/recruitment is severely impaired based upon density-dependent mating success (or Allee effects) is considered a superior approach to the question of how much is enough because of its ecological grounding. However, the successful application of this approach will require re-definition of the space/time scales of the management unit. Finally, support is growing for the establishment of closed areas or “no-take zones” as an alternative approach to managing the problems of fishing a stock complex by enabling sub-populations to escape fishing. While the expected benefits of areas protected from fishing are numerous, clear demonstrations of benefits of such areas in marine temperate ecosystems are lacking. In fact, unintended negative consequences may result from such actions.  相似文献   

8.
Cape anchovy Engraulis encrasicolus adapted its reproductive strategies to the southern Benguela system by spawning over the Agulhas Bank, an area of low productivity that is located upstream of the predominant upwelling system. Frontal jet currents transport eggs and larvae toward the west coast of South Africa, where recruitment takes place. To characterise the recruitment dynamics of Cape anchovy ichthyoplankton, we used an individual-based model forced by a coupled hydrodynamic–biogeochemical model. The results show the importance of food (especially diatoms and copepods) dynamics on the spatial and temporal patterns of recruitment success, and also confirm the importance of the spawning area, timing and water depth on the recruitment success of Cape anchovy larvae.  相似文献   

9.
This study attempts to explain the variability in recruitment of sardine in the northern Benguela and to develop potential models by including environmental information to predict recruitment. Two different recruitment and spawner number datasets were available: a VPA-developed dataset, for the period 1952-1987, and data from a simple age-structured model for 1992-2007. In all, four environmental indices were used: the degree of the intrusion of the warm Angola Current into northern Namibia, termed the Angola-Benguela front index; the extent of the upwelling area off central Namibia; average sea surface temperature (SST) over the northern and central Namibian shelf; and wind stress anomalies at Luderitz as an indicator of upwelling strength. Contrary to general belief, it was found that extremely high recruitment can happen at low spawner levels. This occurred in years in which a large upwelling area existed in association with the minimum southward intrusion of the Angola Current. These effects override the normal negative linear relationships with SST and the positive linear relationship with wind. However, when the area of upwelling is average or small, the effects of spawner biomass, SST and wind become important factors in the variability of recruitment. To estimate exceptional recruitment, the upwelling and front indices were included in the model. To measure medium and weak recruitment, spawner numbers and the SST and wind anomaly formed part of the model. These models can be used simultaneously to predict recruitment before annual acoustic surveys take place and thus aid management decisions.  相似文献   

10.
Seasonal pattern of fish recruitment can vary over years, and the coupling of such pattern with favourable trophic-environmental conditions may trigger non-stationary and non-linear effects on the yearly recruitment variability. The relative contribution of intra-annual discrete recruitment events (REs) to recruitment is often the basis of the inter-annual fluctuations in abundance and biomass of exploited fish populations which are based on a small number of age classes. In this study, REs of European hake (Merluccius merluccius L.) were identified in the north and south of the Balearic Islands (NW Mediterranean) during the 2004 recruitment season and investigated for growth and physiological and morphological condition. Five REs were identified with different contributions in abundance to the annual recruitment in each area coming from different intra-annual spawning batches. Growth rates were similar between the REs with the exception of the last event of the season. Conversely, large differences in morphological and physiological condition were observed between REs and were due to: different environmental-trophic scenarios encountered, and ontogenetic changes related to the recruitment to the shelf-break grounds (ca. 11 cm, 5–6 months of life) which triggered a trade-off in the energy allocation strategy. The spatial-temporal variability in the physiological condition among REs at the beginning of the recruitment season might be explained in the basis on a ‘condition expanded match–mismatch hypothesis’. We advance that individuals recruiting in the north, which were in better condition and temporally and spatially differenced from the south, have most probably hatched in separated locations with different food availability for larvae and early life stages. We propose that hake recruiting to the north and south of the island are from different origins, mainland and the islands respectively, and have benefited from different environmental conditions. This results in a different condition but not in different growth rates.  相似文献   

11.
During 1995–2011, annual production of winter-spring cohort of Ommastrephes bartramii for Chinese squidjigging fishery has greatly fluctuated, which is closely related to the environmental conditions on the spawning and fishing grounds. To better understand how squid recruitment and abundance were influenced by ocean environmental conditions, biological and physical environmental variables including sea surface temperature(SST), SST anomaly(SSTA), chlorophyll a(Chl a) concentration and the Kuroshio Current were examined during years with the highest(1999), intermediate(2005), and lowest(2009) catches. Catch per unit effort(CPUE) of the squid-jigging vessels was used as an indicator of squid abundance. The results indicated that high SST and Chl a concentration on the spawning ground in 1999 resulted in favorable incubation and feeding conditions for squid recruitment. Whereas the suitable spawning zone(SSZ) in 2009 shifted southward and coincided with low SST and Chl a concentration, resulting in a reduction in the squid recruitment. The small difference of SSZ area in the three years suggested the SSZ provided limited influences on the variability in squid recruitment. Furthermore,high squid abundance in 1999 and 2005 was associated with warm SSTA on the fishing ground. While the cool SSTA on the fishing ground in 2009 contributed to adverse habitat for the squid, leading to extremely low abundance. It was inferred that strengthened intensity of the Kuroshio force generally yielded favorable environmental conditions for O. bartramii. Future research are suggested to focus on the fundamental research on the early life stage of O. bartramii and mechanism of how the ocean-climate variability affects the squid abundance and spatial distribution by coupling physical model with squid biological process to explore transport path and abundance distribution.  相似文献   

12.
The recruitment rate of Peruvian anchoveta, Engraulis ringens, was studied to test the hypothesis that long-term environmental variation (regime shifts) had a significant impact on density-dependent processes governing the anchovy recruitment during the period 1963–2004. On the basis of previous defined regimes and turning points for the Humboldt Current System, we identified two groups of years for increased recruitment of anchoveta (1963–1971 and 1986–2004), and one unfavorable period (1972–1985). A common intercept and significantly different slopes were found when the recruitment rate was plotted as a function of the spawning stock biomass during those groups of years, suggesting that density-dependent effects on recruitment were affected during different climate regimes. The favorable (unfavorable) regime was characterized by higher (lower) zooplankton volumes, and with a higher frequency of colder (warmer) waters. Dome-shaped relationships between recruitment rate, spawning stock biomass and SST, were detected with a Generalized Additive Model for the favorable regime. Thus, recruitment could be explained by non-linear effects of environmental variables. Ultimately, climatic regimes are affecting the density-dependent effects on recruitment of anchoveta and the mechanisms involved may be associated with changes in the carrying capacity of the spawning habitat of anchoveta off Peru, which in turn are related with the effects of cold and warm regimes.  相似文献   

13.
A good relationship between the variability in measurements of Cape hake Merluccius capensis biomass during winter and summer swept-area research surveys and sea surface temperature off southern Namibia for the years 1983–1990 is presented. The results call into question the hypothesis that hake density is related to biomass and imply that abnormally warm summers could support higher catches, regardless of the state of the stock. A hypothesis that anomalous warm conditions could induce hake to concentrate closer to the sea bed, making them more susceptible to bottom trawling, is presented.  相似文献   

14.
Control of walleye pollock (Theragra chalcogramma) recruitment in the Eastern Bering Sea involves complex interactions between bottom-up and top-down processes, although the mechanisms are poorly understood. We used statistical models to test the leading hypotheses linking recruitment variability to biotic and abiotic factors. Consistent with a “cold-pool hypothesis”, recruitment of pollock was significantly stronger if winters preceding the larval (age-0) and juvenile stages (age-1) were mild. However, our results did not support the proposed top-down mechanism (cannibalism) underlying this hypothesis. Several empirical relationships support an “oscillating control hypothesis”. As predicted by it, the effect of ice conditions on survival during the larval and early juvenile stages was modified by the abundance of adult pollock, implying stronger bottom-up control when adult abundance (hence cannibalism) was low. The proposed bottom-up mechanism predicts that the survival of pelagic-feeding walleye pollock (benthic-feeding yellowfin sole), should be higher during years with an early (late) ice retreat, which was confirmed by our analysis. Our results also provide additional evidence for a “larval transport hypothesis”, which states that cannibalism of larval and juvenile pollock is reduced in years when strong northward advection separates juveniles from cannibalistic adults.In addition to testing existing hypotheses, we identified new relationships between spawner-to-recruit survival rates of walleye pollock and several indicators of mixed layer dynamics during the spring and summer. Survival rates and recruitment were significantly reduced when larval or early juvenile stages experienced a delay in the (non-ice-associated) spring bloom as a result of stormy spring conditions, suggesting that the timing of the spring bloom is critical to both first-feeding larvae and age-1 juveniles. Furthermore, a dome-shaped relationship between pollock survival and summer wind mixing at the early juvenile stage is consistent with modeling and laboratory studies showing an increase in survival at low to moderate levels of wind mixing, but a decrease in feeding success at high levels of wind mixing.Top-down controls also regulate recruitment of walleye pollock. At least one-third of the variability in spawner-to-recruit survival could be accounted for by predation mortality at the early juvenile stage (age-1). Predation of juvenile pollock can be attributed largely to cannibalism, which varies with the abundance of adult pollock and with the availability of juveniles to adult predators. A simple index reflecting the spatial overlap between juvenile and adult pollock explained 30–50% of the overall variability in recruitment, similar to the variability explained by the best environmental predictors. Although environmental effects are difficult to separate from the effects of predation, we conclude that bottom-up and top-down processes are equally important in controlling the survival of pollock from spawning to recruitment at age 2. However, the magnitude of top-down control is itself modified by environmental factors that control the availability of juvenile pollock to adults (through impacts on spatial distribution) and the abundance of adult predators (through effects on productivity and carrying capacity).  相似文献   

15.
The hypothesis that recruitment variation in flatfishes should be most variable at the northern edge of the species range, least near the centre of the range, and intermediate near the southern limit was tested using stock and recruitment data generated from sequential population analysis for several different flatfish stocks involving four species (plaice Pleuronectes platessa, sole Solea vulgaris from the eastern Atlantic, American plaice Hippoglossoides platessoides, and yellowtail flounder Limanda ferruginae from the western Atlantic). Several groundfish species have been found to conform to this so-called species range hypothesis with the suggestion that density-independent processes predominate at the edges of the distributional range and density-dependent processes dominate in the centre of the range. Our results were generally inconsistent with the hypothesis: the coefficient of variation (CV) of recruitment for plaice in the eastern Atlantic was independent of latitude, the CV of recruitment for sole exhibited a dome-shaped relationship with latitude with the highest CVs occurring at the mid-point of the range, and the CV of recruitment for the western Atlantic stocks exhibited a monotonic decrease with latitude. We extended our latitudinal analyses by assessing both the degree of dependency of recruitment on spawning stock biomass and the spatial and temporal scales of variability in recruitment and pre-recruit survival for the eastern Atlantic stocks. In general our analysis revealed no evidence of a strong stock and recruitment relationship for any of the stocks examined, and previously published analyses revealed no such patterns with latitude. Analysis of both de-trended recruitment and pre-recruit survival time series over the species ranges of sole and plaice revealed strong positive correlations among adjacent stocks and inverse correlations among stocks at the extremes of the range. Recruitment variation in the flatfish stocks examined appears to be dominated by density-independent factors, operating at a local scale, on the egg and larval stages.  相似文献   

16.
This study presents an example of horse mackerel (Trachurus japonicus) stock to demonstrate that marine environmental factors are important in stock assessment for the new Korean Total Allowable Catch (TAC)-based fisheries management system. The estimated survival rate (S) of horse mackerel ranged from 0.25 to 0.36. The instantaneous coefficient of natural mortality (M) was 0.48/year, and the age at first capture was 0.83 year. Annual biomass of horse mackerel in Korean waters was estimated by a biomass-based cohort analysis using annual catch in weight at age during 1965–1995. Yield-per-recruit and spawning biomass-per-recruit were estimated under various harvest strategies at Fmax, F0.1, F30% and F40%. A method for estimating acceptable biological catch (ABC) is proposed for dealing with the large differences in the quality and quantity of information and data available. Using recruitment of horse mackerel estimated from various spawner–recruitment relationship models combined with salinity, volume transport, and zooplankton biomass as environmental factors, the ABC under the best information available was estimated to range from 3100 to 3800 mt.  相似文献   

17.
A review of oceanographic and climate data from the North Pacific and Bering Sea has revealed climate events that occur on two principal time scales: a) 2–7 years (i.e. El Niño Southern Oscillation, ENSO), and b) inter-decadal (i.e. Pacific Decadal Oscillation, PDO). The timing of ENSO events and of related oceanic changes at higher latitudes were examined. The frequency of ENSO was high in the 1980s. Evidence of ENSO forcing on ocean conditions in the North Pacific (Niño North conditions) showed ENSO events were more frequently observed along the West Coast than in the western Gulf of Alaska (GOA) and Eastern Bering Sea (EBS). Time series of catches for 30 region/species groups of salmon, and recruitment data for 29 groundfish and 5 non-salmonid pelagic species, were examined for evidence of a statistical relationship with any of the time scales associated with Niño North conditions or the PDO. Some flatfish stocks exhibited high autocorrelation in recruitment coupled with a significant step in recruitment in 1977 suggesting a relationship between PDO forcing and recruitment success. Five of the dominant gadid stocks (EBS and GOA Pacific cod, Pacific hake and EBS and GOA walleye pollock) exhibited low autocorrelation in recruitment. Of these, Pacific hake, GOA walleye pollock and GOA Pacific cod exhibited significantly higher incidence of strong year classes in years associated with Niño North conditions. These findings suggest that the PDO and ENSO may play an important role in governing year-class strength of several Northeast Pacific marine fish stocks.  相似文献   

18.
The El Niño–Southern Oscillation (ENSO) phase state is reported to drive interannual variability in sea temperatures along South Africa’s south coast through its influence on wind-induced upwelling processes. Whether ENSO drives the intensity of localised, abrupt, intermittent upwelling is less well known. To explore this relationship, we used an index of localised, extreme (>2 °C anomaly), intermittent upwelling intensity, derived from in situ sea temperature data within the Tsitsikamma National Park Marine Protected Area, and quantified the relationship between annual cumulative upwelling intensities (1991–2013) with an annual ENSO index, namely the Southern Oscillation Index. We found that ENSO phase state modulates the cumulative intensity of extreme intermittent upwelling events during an annual period, with more and greater events during La Niña phases compared with El Niño phases. Furthermore, these extreme upwelling events have increased with time along South Africa’s south coast as ENSO phase state becomes more intense and variable. Our findings support the emerging notion that the biological effects of climate change may be manifested through increased environmental variability rather than long-term mean environmental changes as ENSO is predicted to remain the dominant driver of local climate patterns in the future.  相似文献   

19.
Optimal and sustainable management of fish resources cannot be ensured without a thorough understanding of the migration patterns and population (demographic stock) structure. Recent studies suggest that these aspects of the economically and ecologically important deepwater hake Merluccius paradoxus are not reflected in the current assessment and management practices for the Benguela Current Large Marine Ecosystem. In this study, we compiled data from multiple demersal trawl surveys from the entire distribution area and applied state-of-the-art geostatistical population modelling (GeoPop) to estimate growth rate, mortality, and spatial and temporal distribution patterns of M. paradoxus. The data and the model enabled us to follow temporal and spatial changes in the distribution and infer movements from the recruitment/nursery areas, through the juvenile phase and the adults’ migration to the spawning areas outside/upstream of the nursery areas. The results indicated one primary recruitment/nursery area on the west coast of South Africa and a secondary less-productive recruitment/nursery area on the south coast near Port Elizabeth. Juveniles initially migrated away from the main recruitment area, followed by natal homing by larger individuals. This pattern was highly consistent through the time-series of the study. This perception of a, primarily, panmictic population that performs transboundary migrations between Namibia and South Africa corresponds largely to the hypothesis and data plots given in recent studies. We recommend that fisheries assessment, advice and management take into consideration these aspects of the distribution and population (stock) structure of M. paradoxus.  相似文献   

20.
Recruitment of pelagic larval fishes to the nearshore environment is dependent on a suite of biological and physical processes operating at many spatial and temporal scales. Nearshore circulation processes associated with coastal upwelling are widely upheld as major determinants of year class strength for many rockfishes (Sebastes spp.), but the mechanism by which these processes drive recruitment is largely unknown. We used Standard Monitoring Units for the Recruitment of Fishes (SMURFs) to monitor recruitment of two rockfish complexes (Sebastes spp.) and cabezon (Scorpaenichthys marmoratus) from March to September of 2004 and 2005 at 3 sites along the central California coast. We examined the relationship between recruitment of these fishes and measurements of oceanographic variability associated with upwelling dynamics, including in situ water temperature, AVHRR sea surface temperature, the Bakun upwelling index, and an index of alongshore surface water transport. We found that rockfish comprising the KCGB complex (Sebastes atrovirens, Sebastes caurinus, Sebastes carnatus, Sebastes chrysomelas) recruit during early summer, while fishes of the BYO complex (Sebastes melanops, Sebastes flavidus, Sebastes serranoides), as well as cabezon recruit during late summer. Our results provide limited support for an association between the arrival of juvenile pelagic rockfish and cabezon to the nearshore environment and physical processes related to upwelling and relaxation. Beyond the limitations of our bimonthly sampling scheme, the lack of a clear pattern may be related to the near absence of upwelling–relaxation cycles along this stretch of coast during these two study periods. Moreover, the settlement and recruitment of nearshore fishes may be closely tied to processes occurring earlier in the larval stage.  相似文献   

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