Early Life History Strategies Research Articles

Applications of Age–Length Keys for Assigning Ages to Juvenile Steelhead

AbstractMany population metrics for wild steelhead Oncorhynchus mykiss are unquantified due to complex early life history strategies and a lack of juvenile age data. Juvenile steelhead can rear in freshwater systems for up to 7 years, with overlapping size distributions among age‐classes. As logistics for sampling and aging fish can be challenging, there are benefits to utilizing age–length keys (ALKs). We examined the potential benefits of applying ALKs to unaged juvenile steelhead from a rotary screw trap and to determine whether stratifying trapping data by season could improve accuracy in assigning ages to unaged fish. Additionally, we examined the effects of reducing samples of aged fish using a uniform sampling design in which there was a fixed number of aged fish across all length intervals of the size distributions. Using a leave‐one‐out cross validation method with aged fish, we found that ALKs assigned unbiased ages to unaged fish. When including fish with assigned ages from ALKs, results of mean length‐at‐age and brood year abundance estimates between using proportional‐sampled aged fish and uniform‐sampled aged fish were comparable. Typically, absolute differences in estimated brood year abundances were improved if age‐assigned fish were included, and mean absolute error did not exceed 0.4 years for any of the methods examined. Although seasons had a significant effect on mean length at age, overall brood year estimates of juvenile abundance derived from stratifying data by season did not notably differ from pooling summer and fall seasons together, likely because there was a higher portion of juveniles emigrating in the fall compared to the summer. Age–length keys can benefit trapping operations and aid in filling data gaps in age‐based movement and survival for steelhead by being able to accurately assign ages to unaged fish and include more data for population analyses.

Tissue fusion and enhanced genotypic diversity support the survival of Pocillopora acuta coral recruits under thermal stress

Scleractinian coral recruitment provides critical support for reef persistence under the threat of global climate change. The high mortality rates exhibited in early life history stages are further increased under thermal stress, compromising reef recruitment. Tissue fusion with neighboring recruits is one potential early life history strategy that has been shown to support recruit survival (particularly in brooding species) by promoting rapid increases in colony size and potential opportunities for enhanced intracolonial genetic diversity. However, tissue fusion also presents risks in the cost of growth and maintenance of relationships between genetically distinct individuals. Although fusion is one potential strategy for recruit survival, the effects of colony size and enhanced genetic diversity achieved through fusion on survival under ocean warming conditions are not well understood. Here we tested the effect of tissue fusion on Pocillopora acuta recruit survival under ambient and high temperature stress by manipulating the size and parental genotypic richness in fused recruits. We provided opportunities for tissue fusion in groups of recruits with enhanced parental genotypic richness (1–4 parent genotypes) and size (1–4 recruits) and tracked subsequent growth and survival (N = 137). Under ambient temperature (1–15 days post-settlement), fusion significantly increased survivorship regardless of parental genotypic richness, while negative competitive effects existed between closely settled, but unfused recruits. Under high temperature (+ 2.5 °C; 16–47 days post-settlement), the median survival of fused recruits was 5 days longer than individuals, with 1.5 days added to median survival when composed of multiple parental genotypes. These results demonstrate that tissue fusion during coral recruitment can improve survival and provides insights on early life history strategies to increase tolerance to ocean warming.

Diel and tidal periodicity in the responses of early life stages of marine fishes to an estuary opening event in temperate South Africa

Early life stages of fish were monitored in a breach channel during an opening event of the temporarily open/closed East Kleinemonde Estuary. For comparison, early life stages were also collected in the surf zone and estuary mouth region before, during and after the breaching event on a weekly basis. The breach channel was sampled day and night at each midtide state for five consecutive days using a larval fish seine net (mesh 500 µm). Catch per unit effort (CPUE) of mostly postflexion stage larvae increased in the surf zone during opening events with a concomitant peak in abundance in the breach channel. Catch composition included many estuarine associated species typically found in temporarily open/closed estuaries. Predominantly postflexion stage larvae and newly settled juveniles were caught. No overall patterns of diel and tidal use across species were found in the breach channel suggesting some degree of plasticity in recruitment that could be opportunistically driven for most species. However, for the abundant Rhabdosargus holubi (Sparidae), nocturnal flood tides were favoured for movement into the estuary. Natural estuary opening events, especially during peak rainfall in the recruitment season are critical to the early life history strategy of estuary-associated marine fish species.

Spatial and Temporal Influences of Nearshore Hydrography on Fish Assemblages Associated with Energy Platforms in the Northern Gulf of Mexico

In 2013–2014, remote video and diver surveys documented fish assemblages around 150 small oil platforms in nearshore federal waters off the entire Louisiana coast (≤ 18 m depth). Results were used to evaluate ecological processes driving differences in fish abundance and assemblages associated with platforms. The nearshore zone was characterized by high spatial and temporal environmental heterogeneity. Surveys documented 55 species of platform-associated fishes. Twenty-nine species were partially or wholly represented by young-of-the-year (YOY) or age 1–2 juveniles, including red, gray, and lane snapper (Lutjanus campechanus, Lutjanus griseus, and Lutjanus synagris), greater amberjack (Seriola dumerili), and gag grouper (Mycteroperca microlepis). Assemblages were compared among three coastal regions with different hydrography due to interactions between river discharge and bathymetry. Assemblage composition near platforms varied in a region × year interaction associated with inter-annual differences in river discharge and coastal distribution of Sargassum drifts. The probability of YOY L. campechanus occurrence increased with bottom DO saturation (1.40–124.3%) from 0.15 to 0.72. The probability of YOY L. synagris and M. microlepis respectively decreased and increased with depth (5.61–16.76 m) from 0.81 to 0.05 and from 0.03 to 0.68. The results show that fish assemblages around platforms in the nearshore zone experienced substantial inter-regional and inter-annual differences that were driven by hydrographic and recruitment variability. Platforms also provided suitable reef habitat for juvenile fishes in areas that experience widespread bottom water hypoxia and large freshwater inflows, highlighting the importance of nearshore platforms as nursery locations for juvenile fishes that represent a variety of early life-history strategies.

Early life history phenology among Gulf of Alaska fish species: Strategies, synchronies, and sensitivities

Synthesis of four decades of Gulf of Alaska ichthyoplankton data indicates that species diversity and total abundance peaks during spring, a common pattern in temperate and sub-arctic ocean regions due to synchrony with the spring peak in plankton production. Nevertheless, fish larvae occur in the plankton at all times of year and peak abundance periods vary significantly by species and habitat. Larval size at hatching and at transformation to the juvenile stage is also highly variable and associated with a variety of larval durations and temporal supply of larval cohorts to pelagic habitats. This phenological diversity represents variability in exposure and adaptation to seasonal cycles in the ocean. Water temperature, winds and currents, and availability of suitable zooplankton prey vary significantly on a seasonal scale affecting degrees of synchrony among larval species with optimal environmental conditions for growth, transport and survival. This synchrony is also affected by interannual shifts in the oceanographic environment, and different early life phenologies among species generate different sensitivities to such interannual variability. Early life history strategies and synchronies are evaluated here and environmental sensitivities are proposed for the numerically dominant species of fish larvae occurring in Gulf of Alaska plankton, including commercially and ecologically important species. For winter to early spring spawners, cold temperatures are an advantage in terms of slowing development so that larvae do not use up all their lipid reserves prior to optimal availability of suitable larval zooplankton prey. Interannual variability in winter temperature may therefore be a good indicator of survival outcomes, especially as influenced by the timing of the switch to exogenous feeding. Variability in temperature-influenced larval growth during late spring and summer months may be less consequential in maintaining synchrony with larval food availability for spring-summer spawners. Rapid growth in association with warm summer conditions facilitates access to a wide size range of prey organisms and minimizes critical periods of vulnerability to trophic mismatch. The Gulf of Alaska is a highly advective environment; storms and alongshore winds promote onshore advection of surface waters. This onshore Ekman transport is strongest during winter and spring when deep water spawned larvae are most abundant over the slope and require access to the shelf. Enhanced shoreward transport of larvae in the canyons intersecting the slope is also an important mechanism. Interannual variability in such transport mechanisms may be critical in determining early ontogeny survival for these species. During all seasons, but especially spring and summer, there are species of larvae for which retention nearshore is vital for survival and mesoscale oceanographic features as well as larval behavioral abilities may be crucial. Annual patterns in phytoplankton and zooplankton production and abundance indicate high-amplitude variation in the composition of prey fields available to larvae, including variability in abundance and the size spectrum of organisms that larvae might encounter and consume. Food limitation seems less likely for larval species that are most abundant in spring-summer than for species with peak abundance in winter-spring. It is probable that the more selective a species is in terms of zooplankton prey, the more susceptible that species is to a trophic mismatch. Species-specific intrinsic rates and morphological development during early ontogeny also influence the interaction of larvae with their environment, and larval growth trajectories can be quite different even among species with identical early life phenology. This insight clearly indicates that although phenology is critical, timing is not everything and all fish larvae are not equal. For the 23 species and two genera of fish in this study, a synoptic overview is provided of their early ontogeny environmental synchronies and proposed sensitivities. This ecological synthesis of phenologies helps us characterize vulnerability and resilience factors for intervals of the planktonic phase in the pelagic environment. It also identifies environmental signals that could be tested as species-specific ecosystem indicators of population trends for fish stocks in the Gulf of Alaska. Further, understanding seasonal dynamics in the ichthyoplankton is considered important for gauging food availability and energy flow more broadly in this and other pelagic ecosystems, as well as to understanding environmental forcing on the fish populations themselves.

The development and metamorphosis of the indirect developing acorn worm Schizocardium californicum (Enteropneusta: Spengelidae)

BackgroundEnteropneusts are benthic marine invertebrates that belong to the deuterostome phylum Hemichordata. The two main clades of enteropneusts are defined by differences in early life history strategies. In the Spengelidae and Ptychoderidae, development is indirect via a planktotrophic tornaria larva. In contrast, development in the Harrimanidae is direct without an intervening larval life history stage. Most molecular studies in the development and evolution of the enteropneust adult body plan have been carried out in the harrimanid Saccoglossus kowalevskii. In order to compare these two developmental strategies, we have selected the spengelid enteropneust Schizocardium californicum as a suitable indirect developing species for molecular developmental studies. Here we describe the methods for adult collecting, spawning and larval rearing in Schizocardium californicum, and describe embryogenesis, larval development, and metamorphosis, using light microscopy, immunocytochemistry and confocal microscopy.ResultsAdult reproductive individuals can be collected intertidally and almost year-round. Spawning can be triggered by heat shock and large numbers of larvae can be reared through metamorphosis under laboratory conditions. Gastrulation begins at 17 h post-fertilization (hpf) and embryos hatch at 26 hpf as ciliated gastrulae. At 3 days post-fertilization (dpf), the tornaria has a circumoral ciliary band, mouth, tripartite digestive tract, protocoel, larval muscles and a simple serotonergic nervous system. The telotroch develops at 5 dpf. In the course of 60 days, the serotonergic nervous system becomes more elaborate, the posterior coeloms develop, and the length of the circumoral ciliary band increases. At the end of the larval stage, larval muscles disappear, gill slits form, and adult muscles develop. Metamorphosis occurs spontaneously when the larva reaches its maximal size (ca. 3 mm), and involves loss and reorganization of larval structures (muscles, nervous system, digestive tract), as well as development of adult structures (adult muscles, tripartite body organization).ConclusionsThis study will enable future research in S. californicum to address long standing questions related to the evolution of axial patterning mechanisms, germ layer induction, neurogenesis and neural patterning, the mechanisms of metamorphosis, the relationships between larval and adult body plans, and the evolution of metazoan larval forms.

Lack of substrate specificity contributes to invasion success and persistence of Membranipora membranacea in the northwest Atlantic

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 580:117-129 (2017) - DOI: https://doi.org/10.3354/meps12287 Lack of substrate specificity contributes to invasion success and persistence of Membranipora membranacea in the northwest Atlantic Danielle Denley*, Anna Metaxas Department of Oceanography, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada *Corresponding author: danielle.denley@dal.ca ABSTRACT: Selective settlement by planktonic larvae plays a significant role in determining the distribution and abundance of many species of marine invertebrates. For non-indigenous species, larval settlement behavior can determine invasive potential by influencing initial invasion success, secondary spread, and persistence of species outside their native environments. Membranipora membranacea is an ecologically significant invasive bryozoan in the northwest Atlantic, where settlers are most abundant on some but not all species of kelp. Whether the increased abundance of M. membranacea on select kelp species is the result of larval settlement preference remains unknown. In this study, we examine selective settlement by larvae of M. membranacea by (1) quantifying settlers in mixed kelp beds and determining whether larvae settle preferentially with respect to kelp species, (2) conducting laboratory settlement preference experiments using the most abundant kelp substrates in Nova Scotia, and (3) examining whether the presence of kelp beds provides a settlement cue for larvae by quantifying settlement of M. membranacea on plates deployed within and outside of kelp beds. Contrary to settlement behavior described for native populations, our results suggest that larvae of M. membranacea in invaded habitats do not exhibit preference for settling on particular kelp species or within kelp beds. Instead, larvae settle on substrates extending furthest above the primary substratum. Lack of substrate specificity suggests that M. membranacea will continue to persist in the northwest Atlantic despite significant declines in regional kelp abundance. Our results emphasize the importance of early life-history strategies in contributing to invasion success. KEY WORDS: Invasive · Selective settlement · Invertebrate larvae · Life-history strategies · Bryozoans Full text in pdf format Supplementary material PreviousNextCite this article as: Denley D, Metaxas A (2017) Lack of substrate specificity contributes to invasion success and persistence of Membranipora membranacea in the northwest Atlantic. Mar Ecol Prog Ser 580:117-129. https://doi.org/10.3354/meps12287 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 580. Online publication date: September 29, 2017 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2017 Inter-Research.

The three-dimensional structure of Cymodocea nodosa meadows shapes juvenile fish assemblages at Fornells Bay (Minorca Island)

The role of the meadows of the Mediterranean seagrass Cymodocea nodosa as nursery habitats for fish remains largely unknown and there are only few studies investigating the influence of their structure on juvenile assemblages. Here, we monitored juvenile fish assemblages among shallow Cymodocea nodosa meadows (0–1 m) in Minorca Island (north-western Mediterranean Sea) in both July and September 2013. To assess the influence of structural components on juvenile fish assemblages, we selected two different meadow structure types: heterogeneous with intermingled boulders and homogeneous meadows, i.e. without boulders. Juvenile fish assemblages varied significantly among these two meadow structures. Heterogeneous meadows had higher total juvenile density and species richness, where some species were only found in these portions, such as Coris julis and Serranus spp. Other species, such as Symphodus spp. and Sarpa salpa, were also more abundant within heterogeneous meadows. However, densities of some species were not increased in heterogeneous meadows demonstrating a specific response to habitat structure. For instance, Diplodus annularis displayed similar abundances in both heterogeneous and homogeneous portions of the meadow. Our study reveals that the intrinsic structural variability of seagrass meadows plays a key role for the assemblage of several fish species that are characterized by different early life history strategies.

Early life history traits of Harpagifer antarcticus (Harpagiferidae, Notothenioidei) from the South Shetland Islands during austral summer

The Antarctic spiny plunderfish Harpagifer antarcticus is a common species distributed along the southern Scotia Arc, representing one of the most important components of the littoral benthic fish community there. Compared to adulthood, the early life history traits of H. antarcticus are poorly known, especially for the population inhabiting the shallow waters off the South Shetland Islands. Through the analysis of sagittal otolith microstructure, we estimated age and growth from early larvae collected during the austral summer at Chile Bay, Greenwich Island. An exponential model fitted to the age–length data provided estimates of hatching size and mean larval growth of the local population, being, respectively, 5.36 mm and 0.17 mm day−1 (range 0.12–0.22 mm day−1), corresponding to a daily percentage increase in body size of 2.2%. Back-calculated hatch dates were positively correlated to wind intensity, especially in case of northeast wind dominance. Based on this evidence, we suggest that hatching of H. antarcticus might be triggered by wind-induced turbulence in nearshore subtidal environments of the South Shetland Islands. From an ecological perspective, the early life history strategy of this species consisted of a spring–summer hatching of small, fast-growing larvae, which develop into a demersal juvenile stage before their first winter of life.

Maternal contribution to spawning and early life-history strategies of the genus Lepidonotothen (Nototheniidae, Perciformes) along the southern Scotia Arc

The coastal fish community of the southern Scotia Arc, including the South Shetland Islands and the Bransfield Strait, is composed of the genus Lepidonotothen, which consists of three widely overlapping species such as L. kempi, L. larseni and L. nudifrons. The life-history strategies of these species driven by environmental and inter-specific interactions remain poorly known. In this paper, we estimate the maternal contribution to spawning of adult females in terms of fecundity and egg size through macroscopic and histological analyses of gonads. We further investigate the size and timing of hatching, growth rate and duration of the larval stage through microstructure analysis of sagittal otoliths collected from larval samples. All three species produced eggs of relatively small size at hatching, showing a trade-off between egg size and fecundity. Total fecundity was positively related to fish size during growth, as well as to maximum size. Female gonad investment was comparable among the species, as they all start spawning at about 65% of their maximum size with a similar gonadosomatic index. All species generated small larvae (altricial) which hatched over widely different periods, resulting in a temporal succession of larval occurrence. Compared to L. kempi, the other two species had relatively slow-growing larvae. Only L. kempi and L. larseni produced overwintering larvae. Differences in maternal contribution to spawning and early life-history traits of these species contribute to reduce interspecific competition for food through ecological niche partitioning.

Effects of Temperature, Total Dissolved Solids, and Total Suspended Solids on Survival and Development Rate of Larval Arkansas River Shiner

Abstract Decreases in the abundance and diversity of stream fishes in the North American Great Plains have been attributed to habitat fragmentation, altered hydrological and temperature regimes, and elevated levels of total dissolved solids and total suspended solids. Pelagic-broadcast spawning cyprinids, such as the Arkansas River Shiner Notropis girardi, may be particularly vulnerable to these changing conditions because of their reproductive strategy. Our objectives were to assess the effects of temperature, total dissolved solids, and total suspended solids on the developmental and survival rates of Arkansas River Shiner larvae. Results suggest temperature had the greatest influence on the developmental rate of Arkansas River Shiner larvae. However, embryos exposed to the higher levels of total dissolved solids and total suspended solids reached developmental stages earlier than counterparts at equivalent temperatures. Although this rapid development may be beneficial in fragmented waters, our data suggest it may be associated with lower survival rates. Furthermore, those embryos incubating at high temperatures, or in high levels of total dissolved solids and total suspended solids resulted in less viable embryos and larvae than those incubating in all other temperature, total dissolved solid, and total suspended solid treatment groups. As the Great Plains ecoregion continues to change, these results may assist in understanding reasons for past extirpations and future extirpation threats as well as predict stream reaches capable of sustaining Arkansas River Shiners and other species with similar early life-history strategies.

Feeding ecology of larval Atlantic bluefin tuna, <I>Thunnus thynnus,</I> from the central Gulf of Mexico

Inter-annual and ontogenetic differences in diet and feeding intensity were examined for larval Atlantic bluefin tuna, Thunnus thynnus (Linnaeus, 1758), collected from the central Gulf of Mexico (GOM) during May 2008, 2009, and 2010 [n = 100; 3.0–6.7 mm body length (BL)]. Predominant prey groups were copepods, cirripeds, and cladocerans. Inter-annual differences in diet resulted from changes in the consumption of copepods and unique prey groups (e.g., cladocerans). Body length had an effect on T. thynnus diet, and a relative increase in copepod consumption occurred beyond 5 mm. Feeding intensity (i.e., the number of prey per digestive tract) was higher during 2010 than 2008 and 2009 and positively correlated with increasing T. thynnus BL. No fish prey were observed, which suggests piscivory in GOM T. thynnus does not occur at sizes <6 mm. Patterns in feeding incidence (i.e., total number of digestive tracts with prey divided by the total number of digestive tracts) contrasted with reports from the Mediterranean Sea, suggesting T. thynnus may have distinct early life history strategies between the two regions.

Fish community of a small, temperate, urban river in South Africa

Freshwater and marine-spawned fishes were sampled from the Baakens River, a small urban river that runs through the city of Port Elizabeth in the Eastern Cape of South Africa. Using fyke nets, 8 sites were sampled along the river course over a 4-month period (January – April 2014). Catches were comprised of indigenous freshwater, marine migrant and alien fishes. Marine migrant fishes, including catadromous species dependent on freshwater for early life-history strategies, were significantly affected by instream barriers which prohibited upstream migration of all species except Anguilla mossambica. The freshwater fish fauna was dominated by Tilapia sparrmanii and Pseudocrenilabrus philander, species that are alien to the Baakens River. While indigenous Barbus pallidus and Sandelia capensis were both abundant and widely distributed in the river, only two Pseudobarbus afer were sampled from one survey site. The low abundance and narrow distribution of this endangered species is of concern and human-mediated impacts on this species require urgent evaluation and mitigation. Keywords : Baakens River, migration barrier, weir, alien fish, endangered fish

Diverse Early Life-History Strategies in Migratory Amazonian Catfish: Implications for Conservation and Management.

Animal migrations provide important ecological functions and can allow for increased biodiversity through habitat and niche diversification. However, aquatic migrations in general, and those of the world’s largest fish in particular, are imperiled worldwide and are often poorly understood. Several species of large Amazonian catfish carry out some of the longest freshwater fish migrations in the world, travelling from the Amazon River estuary to the Andes foothills. These species are important apex predators in the main stem rivers of the Amazon Basin and make up the region’s largest fishery. They are also the only species to utilize the entire Amazon Basin to complete their life cycle. Studies indicate both that the fisheries may be declining due to overfishing, and that the proposed and completed dams in their upstream range threaten spawning migrations. Despite this, surprisingly little is known about the details of these species’ migrations, or their life history. Otolith microchemistry has been an effective method for quantifying and reconstructing fish migrations worldwide across multiple spatial scales and may provide a powerful tool to understand the movements of Amazonian migratory catfish. Our objective was to describe the migratory behaviors of the three most populous and commercially important migratory catfish species, Dourada (Brachyplatystoma rousseauxii), Piramutaba (Brachyplatystoma vaillantii), and Piraíba (Brachyplatystoma filamentosum). We collected fish from the mouth of the Amazon River and the Central Amazon and used strontium isotope signatures (87Sr/86Sr) recorded in their otoliths to determine the location of early rearing and subsequent. Fish location was determined through discriminant function classification, using water chemistry data from the literature as a training set. Where water chemistry data was unavailable, we successfully in predicted 87Sr/86Sr isotope values using a regression-based approach that related the geology of the upstream watershed to the Sr isotope ratio. Our results provide the first reported otolith microchemical reconstruction of Brachyplatystoma migratory movements in the Amazon Basin. Our results indicate that juveniles exhibit diverse rearing strategies, rearing in both upstream and estuary environments. This contrasts with the prevailing understanding that juveniles rear in the estuary before migrating upstream; however, it is supported by some fisheries data that has indicated the presence of alternate spawning and rearing life-histories. The presence of alternate juvenile rearing strategies may have important implications for conservation and management of the fisheries in the region.

Early life history pelagic exposure profiles of selected commercially important fish species in the Gulf of Alaska

A synthesis of nearly four decades of ichthyoplankton survey data from the Gulf of Alaska was undertaken to provide the most comprehensive information available on the early life history ecology of five focal species: Pacific Cod (Gadus macrocephalus), Walleye Pollock (Gadus chalcogrammus), Pacific Ocean Perch (Sebastes alutus), Sablefish (Anoplopoma fimbria), and Arrowtooth Flounder (Atheresthes stomias). This analysis of historical data, along with information from published studies, is presented here in the form of ecological reviews of the species during their planktonic phase. The reviews include descriptions of temporal and spatial patterns of exposure to the environment, and interpretation regarding associated sensitivities to environmental forcing. On a temporal scale, patterns in abundance of eggs and larvae are synthesized that characterize seasonal exposure to the pelagic environment, and interannual variation that is presumed to incorporate responses to long-term environmental forcing. Spatial patterns are synthesized to identify horizontal and vertical extent of egg and larval distributions, delineate areas of primary larval habitat, and illuminate egg and larval drift pathways. The observed patterns are discussed with respect to characterizing species early life history strategies, identifying long-term adaptations to the Gulf of Alaska environment, and associated resilience and vulnerability factors that may modulate early life responses to environmental forcing in this region. For each species, gaps in knowledge are identified and are concerned primarily with the period of transition between the larval and juvenile stage, and feeding habits and ecology across seasons, habitats and sub-intervals of early ontogeny. These early life history reviews advance our ecological understanding of the pelagic phase, and fine-tune our focus for the investigation of potential response mechanisms to environmental forcing at appropriate, species-specific temporal and spatial scales.

Early life history traits ofTrematomus scottiin the Bransfield Strait

AbstractEarly life history traits of the blackfin notothen,Trematomus scotti, were investigated through otolith microincrement pattern and stomach content analyses. Post-larval specimens of 12–20 mm standard length (SL) were collected in the Bransfield Strait and adjacent waters during the 2010–11 summer. Catches were unevenly distributed across the surveyed area, yielding a relative abundance of 0.3–3.6 specimens per 1000 m3of filtered sea water. Age estimates ranged from 34 to 67 days, with good consistency and no apparent bias between readings. Based on an exponential model fitted to the age-length dataset, the growth rate was 0.17 mm day-1, corresponding to a daily percentage increment in size of 1.07% SL. In agreement with previous studies, larval hatching occurred at a mean size of 9.0 mm and was spread over a relatively short period, lasting from late December to late January. Prey composition consisted exclusively of copepods, mainly larval stages of copepodites. Feeding intensity ranged from 1–14 prey items per stomach, being positively correlated with larval fish size. In summary,T. scottishares a common early life history strategy with several other notothenioids, consisting of small larvae hatching in summer and overwintering as pelagic early juveniles until the following summer season.

The complex early life history of a marine estuarine-opportunist fish species, &lt;em&gt;Solea turbynei&lt;/em&gt; (Soleidae) from temperate South Africa

The early life history stages and ecology of Solea turbynei , a marine estuarine-opportunist species, is described from nursery areas in Algoa Bay, South Africa. Early life history stages were collected over multiple years from known nursery habitats using plankton, fyke and larval seine nets. The larvae are described using morphometric measurements, meristic counts and pigmentation based on 29 individuals. Solea turbynei is differentiated from other Soleidae by the small size at flexion (3-4 mm), low myomere count and presence of two characteristic blotches of pigment on the dorsal fin. This species has a unique early life history strategy in that the larvae progressively span nearshore, surf zone and estuarine habitats with ontogeny. Abundance of preflexion stages peaks in summer in nearshore waters, indicative of peak spawning period but preflexion larvae are present throughout the year, indicating protracted spawning by adults. At flexion stage, larvae utilize surf zones where metamorphosis and settlement takes place. Early juveniles migrate into the sandy lower reaches of estuaries, after which fish take up residency to adulthood. Warm water is important for larval growth and survival in the nearshore, while turbidity shows a positive relationship with recruitment into estuarine nurseries.

"Beyond cumulative risk: Distinguishing harshness and unpredictability as determinants of parenting and early life history strategy": Correction.

"Beyond cumulative risk: Distinguishing harshness and unpredictability as determinants of parenting and early life history strategy": Correction.

Beyond cumulative risk: Distinguishing harshness and unpredictability as determinants of parenting and early life history strategy.

Drawing on life history theory, Ellis and associates' (2009) recent across- and within-species analysis of ecological effects on reproductive development highlighted two fundamental dimensions of environmental variation and influence: harshness and unpredictability. To evaluate the unique contributions of these factors, the authors of present article examined data from a national sample 1364 mothers and their children participating in the NICHD Study of Early Child Care and Youth Development. Harshness was operationalized as income-to-needs ratio in the first 5 years of life; unpredictability was indexed by residential changes, paternal transitions, and parental job changes during this same period. Here the proposition was tested that these factors not only uniquely predict accelerated life-history strategy, operationalized in terms of sexual behavior at age 15, but that such effects are mediated by change over the early-childhood years in maternal depression and, thereby, observed maternal sensitivity in the early-elementary-school years. Structural equation modeling provided empirical support for Ellis et al.'s (2009) theorizing, calling attention once again to the contribution of evolutionary analysis to understanding contemporary human parenting and development. Implications of the findings for intervention are discussed.

Early fish growth varies in response to components of the flow regime in a temperate floodplain river

Summary 1. The biological productivity of floodplain rivers is intimately related to their flow regimes and it has been proposed that fish production should be linked to components of the flow regime in productivity models. To assess applicability of existing models of productivity in floodplain rivers, we tested predictions about growth during the early life stages of a common, short-lived fish (Australian smelt Retropinna semoni) in a non-flow-altered, temperate Australian floodplain river. 2. The morphometric condition of larval and juvenile fish measured over a five-year period was positively related to annual discharge, but the highest average seasonal growth rates occurred in two years of contrasting hydrology, one with early spring flooding and the other with predominantly low flows and a late season (within channel) flow pulse. 3. Analysis of daily growth measures indicated that timing, river height, the duration of in-channel flow events and antecedent flood events are all significant factors influencing the early growth of Australian smelt. The flexible manner in which fish growth responds to these factors appears to be an effective early life history strategy for a short-lived species occupying a highly variable environment. 4. Growth rates conformed to some predictions of the Flood Pulse Concept (in particular the Extended Flood Pulse Concept), but specific growth responses suggest that the Riverine Productivity Model and tenets of the Low Flow Recruitment Hypothesis best describe the production of Australian smelt in this system. We suggest that none of the existing conceptual models adequately describes fish productivity in temperate Australian floodplain rivers but that aspects of each are likely to be relevant under different flow conditions.