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Overfishing causes a significant decline in blue swimming crab (Portunus pelagicus) populations, an essential marine resource for Thailand. This research aimed to identify suitable nursery areas for this species throughout the four distinct monsoon seasons. This is the first comprehensive study of habitat characteristics: water temperature, pH, salinity, dissolved oxygen, marine sediment, seagrass beds, and suitability assessment of nursery areas, using a combined approach of Analytic Hierarchy Process and Geographic Information Systems. Our findings reveal that highly suitable nursery habitats comprise a small percentage of the total study area, varying with the monsoon season: 1.66% in the Northeast Monsoon (NEMS), 1.00% in the NEMS transition (NEMST), 1.11% in the Southwest Monsoon (SWMS), and 1.97% in the SWMS transition (SWMST). These areas are concentrated along the coastlines of Sed Island, Phum Riang, Takrob, Tha Thong, and Donsak. Sed Island was designated as a fishery refuge zone in 2022. The identified nursery areas coincide with existing crab banks, highlighting the model's accuracy. Conversely, unsuitable areas were predominantly in shellfish farming zones and low-salinity estuaries. By identifying suitable nursery grounds for the blue swimming crab, this study offers valuable information that can support Thailand's sustainable management and conservation efforts for this species. Doi: 10.28991/HEF-2024-05-03-01 Full Text: PDF

Nursery habitats play a significant role in completing fish life cycles, and they are now recognized as essential habitats. Monthly variations in nursery ground distributions of Larimichthys polyactis were investigated in the southern Yellow Sea in 2019. Bayesian hierarchical models with integrated nested Laplace approximation were utilized to model the preferential nursery habitats of L. polyactis larvae. The study analyzed the spatial and temporal distributions of the larvae and juveniles based on three environmental variables: sea surface temperature, sea surface salinity, and depth. Additionally, this study examined the utilization of habitats by different fish life stages and ontogenetic shifts. A total of 3240 individuals were collected from April to June, with the peak occurring in May (0.05 ind./m3), and the distribution areas varied between different months. The prediction of the model reveals the ecological adaptability of L. polyactis to temperature variations. The optimal temperature for L. polyactis density ranges from 12.5 °C to 16.5 °C in April and 16.5 °C to 17.5 °C in May, demonstrating a broad temperature tolerance for L. polyactis survival. In addition, there are variations in distribution patterns among different developmental stages. Larimichthys polyactis spawn in the inshore and nearshore waters, and after hatching, larvae in the pre-flexion stage tend to remain aggregated near the spawning beds. However, larvae in the advanced development stage (post-flexion) and juveniles move towards the sandy ridge habitats along the coast and start to migrate offshore in June. This study provides valuable insights for the effective management of fishery resources in the area and can be utilized to identify marine areas with specific habitat features that require conservation. [ABSTRACT FROM AUTHOR]

The blackchin guitarfish Glaucostegus cemiculus has suffered severe declines and regional extirpation throughout its known distributions. While this species and its relative, the common guitarfish Rhinobatos rhinobatos, have been described in the Mediterranean Sea with co-occurring habitat ranges, no research has recorded the existence or extent of these two separate populations along the Israeli coastal waters. Along a particular coast in Israel, Ma’agan Michael, fishermen have reported annual observations of juvenile guitarfish between June to November for the last forty years. Based on these citizen-based observations themain research objective is to establish whether Ma’agan Michael fulfils all three criteria fromthe literature by Dr Michelle Heupel, allowing it to be acknowledged as a nursery ground for G. cemiculus. The methodology built for this objective integrates biological characteristics data with the identification of a recurrent seasonal distribution. Visual surveys exhibited a significantly higher abundance in Ma’agan Michael when compared to an adjacent area (Caesarea), with 2,096 recorded observations overall. Additionally, using a species-specific modified Catch and Release protocol, a total of 492 juveniles were captured with a beach seine net. During these capturing events, individuals were morphometrically measured and sampled for future genetic analyses. Out of these, 327 specimens were also fitted for PIT tags to track recaptures in subsequent captures. The highest abundance of neonates was caught from August to September each year (2017–2019), and all individuals captured during this study were identified in the field as G. cemiculus, ranging from 20–35 cm in length (85% of captures). Many specimens had an umbilical cord scar (n = 88), with a large percentage possessing visual remains of the yolk sac. For the first time, this study provides an inter-year description of the species Glaucostegus cemiculus present along the Israeli shoreline. [ABSTRACT FROM AUTHOR]

Tropical mangroves are known to support fish production, but natural variability in the link between mangrove habitats and fish populations undermines our ability to manage, conserve and restore this ecological relationship. This is largely due to undefined context‐dependence in the use of mangroves by fish. We collected a spatially extensive dataset of 494 mangrove fish assemblages using standardised Remote Underwater Video surveys of mangrove edge habitats from five environmentally heterogenous regions in the Indo‐Pacific. We used machine learning methods to define contextual limits of the use of mangroves by reportedly mangrove‐affiliated fish. We found that tidal range and proximity to coral reefs were the most important contextual predictors of the use of mangroves by most taxa. We established data‐driven threshold values for important contextual predictors of the use of mangroves by fish, offering new insights into the variable role played by tropical mangroves in supporting fish life histories. Where mangroves occur as part of reef seascapes in regions with limited tidal range (<1.5 m), they appear to serve an important juvenile habitat function for a wide spectrum of reef fish. In regions with substantially larger tidal ranges, mangroves appear to only support certain reef species with coastal life histories. Coastal and estuary fish were able to use mangroves in a wide variety of non‐reef contexts. We demonstrate that key thresholds in environmental context can govern the functional role of mangroves, with strong implications for the role of other habitats in coastal seascapes. [ABSTRACT FROM AUTHOR]

The study reports on the capture of a new-born specimen of shortfin mako shark Isurus oxyrinchus Rafinesque, 1810 off Karantina islet coast, Urla, Izmir (north Aegean Sea). This specimen measured 761 mm in total length and weighed 2900 g. The historical and recent captures of the species in the area shows the presence of new-born, juvenile and adult males and females. The distribution of these specimens suggests the potential occurrence of a nursery ground in the same area. To preserve the extirpation of the species throughout the area where it finds favourable environmental parameters to live, a management plan should be conducted to ensure the establishment of a viable population in the Turkish marine waters. [ABSTRACT FROM AUTHOR]

The blackchin guitarfish Glaucostegus cemiculus has suffered severe declines and regional extirpation throughout its known distributions. While this species and its relative, the common guitarfish Rhinobatos rhinobatos, have been described in the Mediterranean Sea with co-occurring habitat ranges, no research has recorded the existence or extent of these two separate populations along the Israeli coastal waters. Along a particular coast in Israel, Ma’agan Michael, fishermen have reported annual observations of juvenile guitarfish between June to November for the last forty years. Based on these citizen-based observations the main research objective is to establish whether Ma’agan Michael fulfils all three criteria from the literature by Dr Michelle Heupel, allowing it to be acknowledged as a nursery ground for G. cemiculus. The methodology built for this objective integrates biological characteristics data with the identification of a recurrent seasonal distribution. Visual surveys exhibited a significantly higher abundance in Ma’agan Michael when compared to an adjacent area (Caesarea), with 2,096 recorded observations overall. Additionally, using a species-specific modified Catch and Release protocol, a total of 492 juveniles were captured with a beach seine net. During these capturing events, individuals were morphometrically measured and sampled for future genetic analyses. Out of these, 327 specimens were also fitted for PIT tags to track recaptures in subsequent captures. The highest abundance of neonates was caught from August to September each year (2017–2019), and all individuals captured during this study were identified in the field as G. cemiculus, ranging from 20–35 cm in length (85% of captures). Many specimens had an umbilical cord scar (n = 88), with a large percentage possessing visual remains of the yolk sac. For the first time, this study provides an inter-year description of the species Glaucostegus cemiculus present along the Israeli shoreline.

Sustainable fisheries management seeks to balance fisheries' conservation with fishers' economic well‐being. Marine protected areas are increasingly used as a component of management frameworks to improve the resilience of, or maintain, marine resources. However, any spatial management measures need to consider the seasonal distribution of key species at key life stages, such as the recruitment stage.Trichiurus japonicus (hairtail) is the highest yielding single fish species in China, but it is showing signs of miniaturization and early maturity, which are indicators of overfishing. Thus, it is a suitable model species for studies aiming to find a solution to the challenge of balancing fishing activities with resource protection.The potentially important seasonal nursery grounds of T. japonicus in the East China Sea were identified using a model combining data for the variability in abundance and the probability of occurrence of T. japonicus recruits. Based on fishery‐independent survey data, a Bayesian hierarchical species distribution model revealed that the locations and sizes of core nursery grounds of T. japonicus varied seasonally and that the main drivers were depth, sea bottom temperature and sea bottom salinity.The possible seasonal interactions between fishing effort and nursery grounds at different levels of importance were evaluated by analysing the spatial overlap between fishery hot spots and T. japonicus core nursery grounds. The results showed that the proportion of overlap was highest in spring and lowest in summer.These findings highlight the urgent need to develop fleet‐adapted management measures for different levels of overlap and suggest that the eastern and southern areas of the East China Sea hairtail national aquatic germplasm resources conservation zone (TCZ) should be included in conservation planning. [ABSTRACT FROM AUTHOR]

Although elasmobranchs (sharks and rays) are highly threatened by fisheries, there are few studies that examine gear and fishery effects on catch composition and abundance across India, one of the top elasmobranch fishing nations globally. We assessed elasmobranch diversity, abundance, catch rates and fishery characteristics using landing surveys in Malvan on the central‐western coast of India, a major multi‐gear, multi‐species fishing centre, over three sampling periods from February 2018 to March 2020. We sampled 3145 fishing trips and recorded 27 elasmobranch species, of which nearly half are categorised as "Threatened" by the IUCN. In addition, we documented historical records by compiling information from identification guides, research papers, articles and reports. During the study period, the catch was dominated by small‐sized coastal species like the spadenose shark (Scoliodon laticaudus) and the scaly whipray (Brevitrygon walga). Trawlers accounted for 64.9% of the catch, highest by number, and captured smaller‐sized individuals. Nonetheless, artisanal and gillnet fisheries had higher catch per unit effort (CPUE) for rays (5.1 ± 1.0) and sharks (10 ± 1.0), respectively, and captured significantly larger‐sized individuals. Through generalised linear models, we found seasonal, gear and fishery effects on the abundance and size of commonly caught species. The presence of neonates and gravid females of multiple species also suggests nursery grounds in this region. Historically, 141 species have been recorded in this region, and a comparison with current catch suggests a shift in elasmobranch community structure and potential mesopredator release. This study emphasises the importance of gear and species‐specific research for conservation planning at the local level and suggests the need for management strategies with fisher cooperation. [ABSTRACT FROM AUTHOR]

The northern Satsunan area, comprising the mouth of Kagoshima Bay and Osumi Strait, is an important spawning and nursery ground for Japanese jack mackerel Trachurus japonicus in Japan. Upwellings frequently occur at the mouth of the bay during winter and spring, and the consequent nutrient supply promotes phytoplankton blooms. This study examined how T. japonicus utilizes upwelling (Kagoshima Bay) and non-upwelling areas (Osumi Strait) as larval nursery grounds. Densities and growth rates (measured as the average width of the last three otolith increments) of T. japonicus larvae in both areas were compared to determine the upwelling influence on nursery ground formation. The mouth of the bay had lower temperature and salinity but higher chlorophyll-a concentrations and prey density than that of the strait. Densities of larvae were consistently higher in the bay than in the strait, indicating that the main nursery of T. japonicus is formed in Kagoshima Bay. No significant differences were observed in the growth rates of larvae among areas, suggesting that lower temperatures and prey availability are growth limiting factors in the mouth of the bay and the strait, respectively, and the Osumi Strait could also provide a favorable nursery area. [ABSTRACT FROM AUTHOR]

Extreme environmental conditions, such as high and low salinity, are stressors for marine fish growth. Juveniles of marbled flounder Pseudopleuronectes yokohamae and stone flounder Platichthys bicoloratus use estuaries as nursery grounds. Our field surveys showed that the occurrence of juvenile stone flounder seemed to be unrelated to salinity, whereas that of juvenile marbled flounder was positively correlated with salinity. To examine the effects of salinity on feeding and growth of these species, we conducted a laboratory experiment in which juveniles were reared individually under constant and variable salinity regimes for seven days. Cultured marbled flounder of two sizes (23–29 and 48–58 mm standard length) were reared under constant salinities of 5, 15, and 30 and fluctuating salinities of 5–30 and 15–30 or 5–15. Wild stone flounder (23–37 mm standard length) were reared under constant salinities of 1, 5, and 30 and fluctuating salinities of 5–30 and 1–30. Commercial pellets were fed to fish twice daily until satiation. The feeding and growth of marbled and stone flounders were considerably low at constant salinities of 5 and 1, respectively. Meanwhile, suppression of feeding and growth was not observed in fish with salinities varying from 5 to 30 or 1 to 30, respectively. The results indicated that extremely low salinity inhibits feeding and growth of juveniles only with continuous exposure. Estuaries with fluctuating salinities are potential nursery grounds for both marbled flounder and stone flounder, although marbled flounder tend to avoid low-salinity environments in the field. This study showed that extremely low-salinity environments, which reduce juvenile growth when consistently exposed, would not affect distribution or growth if they were temporary around low tide. [Display omitted] • Juvenile stone flounder occurred at wider salinity ranges than marbled flounder. • Feeding and growth of juveniles were reduced under extremely low salinities. • Juvenile growth inhibition did not occur at fluctuating salinity treatments. • Temporary low salinity environment does not hinder habitat use of juveniles. [ABSTRACT FROM AUTHOR]

Context: Shark pupping and nursery grounds are essential habitats, yet these areas are undocumented for deepwater species. Young juveniles of black dogfish (Centroscyllium fabricii) were found to be dominant in the Laurentian Channel, prompting an analysis of their distribution in Canadian waters of the Northwest Atlantic. Aims: This study documents patterns of distribution by sex and life stage for black dogfish in shelf and slope waters of Canada. Methods: Over 40 years of trawl survey data from the Canadian Department of Fisheries and Oceans (DFO) Newfoundland and Labrador Region was analysed to document patterns of distribution of black dogfish by sex and life stage. Key results: Free-swimming neonates were found in the Laurentian Channel, along with adult females, including some with pups, indicating that the Laurentian Channel is the pupping grounds for this species. Small black dogfish, highly abundant in the Channel, is largely absent in slope waters, indicating that the Channel is the nursery ground for black dogfish in Canada. Conclusions: As they grows, black dogfish individuals undergo a multi-year distributional shift extending over ∼4000 km, originating in the Laurentian Channel out to slope waters, with the largest fish being found furthest from the Channel. No other deep demersal chondrichthyans are known to undergo a progressive migration as they grow, more akin to pelagic sharks where separate pupping–nursery grounds and long-distance migrations are commonly documented. Implications: The segregation by life stages shown in the present study differs from previously reported distribution patterns of black dogfish in Greenland and Iceland. Given warm and stable ambient temperatures in the Channel, similar to slope waters, black dogfish is stenothermal, maintaining a narrow thermal profile throughout its life. Identifying the essential habitats of pupping and nursery grounds is crucial to the management and conservation of this species. Black dogfish off Canada undergoes a multi-year distributional shift, starting in the Laurentian Channel pupping grounds–nursery area, then spreading out along slope waters, with the largest fish being found furthest from the Channel, up to 4000 km away. No other deep demersal species are known to have a dedicated nursing ground–pupping area or to undergo a progressive migration as they grow. [ABSTRACT FROM AUTHOR]

This study assessed the effects of tidal stages and habitat conditions on nekton assemblage and distribution in the Kakum River estuarine mangrove system in the Central Region of Ghana. Teleosts and crustaceans were sampled using pole seine and cast net from a tidal mangrove pond and a channel, and characterised using morphometry and ecological guilds concept. In total, 1 146 specimens were collected, with 35 species from 19 families represented. The most abundant species encountered were Liza spp. (Mugilidae; 36%), Sarotherodon melanotheron (Cichlidae; 16%), Elops lacerta (Elopidae; 6%) and Sardinella aurita (Clupeidae; 5%), which exhibited pronounced spatial distribution. Sarotherodon melanotheron showed preference for ponds with minimal water flow and depth, Sardinella aurita occurred only in deeper sections of the mangrove channel with significant flow velocity, and Elops lacerta in the pond and all channel stations. Mugilids were found exclusively in the channel, whereas Palaemonidae (Macrobrachium macrobrachion and M. vollenhoveni) occurred in specific locations in the channel, with species- specific preferences for tidal stages. Most species encountered were identified to be predominantly marine migrants with bentophagous feeding habit. Site selection and tidal stages were found to affect the occurrence and distribution of fishes over a tidal cycle and interactively influence species diversity. [ABSTRACT FROM AUTHOR]

Both beach seine (BS) and line transect-based underwater visual census (UVC) methods were applied to investigate fish assemblages of the West Sand (Xisha Islands, South China Sea) seagrass meadows and their relationship with seagrass coverage. The West Sand seagrass meadows were divided into four survey areas, two (areas A and B) to the north and two (areas C and D) to the south. The average seagrass coverages (%) in the north were significantly higher than those in the south (p < 0.05). The dominant seagrass species is Thalassia hemprichii, contributing to over 70% substrate coverage in all four areas. A total of 843 individuals from 25 fish species belonging to 22 genera, 11 families, and ten orders were recorded, with five species obtained by both BS and UVC methods. The labrids Halichoeres trimaculatus and Stethojulis strigiventer were the only two species that dominated (index of relative importance IRI > 500) in both BS and UVC methods. Fish assemblages among the four areas were significantly different (BS, p = 0.002; UVC, p = 0.002); area A was significantly different from areas B−D (p < 0.05), which was mainly driven by the variation in H. trimaculatus density. Furthermore, fish assemblages of the four areas (abundance data) revealed by both BS (r2 = 0.8455) and UVC (r2 = 0.9354) methods showed high correlation with the seagrass coverage. The majority of the individuals (>93%) recorded by BS and UVC methods were shorter than the total length at maturity (TLm), with 80.36 and 46.13% of individuals less than half the sizes of their TLm, respectively. Our results, for the first time, proved the importance of seagrass meadows at the West Sand as fish nursery grounds. The ecological roles of seagrass habitats in South China Sea merit further investigation.

To evaluate the importance of the northern Satsunan area in southern Japan as a spawning and nursery ground for chub mackerel (Scomber japonicus), we investigated the early life history characteristics (e.g., larval distribution, feeding habits, and growth) of S. japonicus over five successive years. This area is considered the main habitat and spawning ground of the congeneric species, S. australasicus. Using polymerase chain reaction-restriction fragment length polymorphism analysis, we first confirmed that S. japonicus larvae were abundant in the northern Satsunan area, potentially representing a major spawning and nursery ground in the Japanese Pacific coastal area. The number of recorded larvae started to increase in 2016, corresponding to the population dynamics of the Pacific stock of the species, which has shown increasing trends in recent years. Morphological and DNA metabarcoding analyses of gut contents and stable isotope analysis showed that, in addition to copepods, the larvae fed substantially on appendicularians. The trophic pathway involving appendicularians might support the feeding habits of S. japonicus, promoting its coexistence with other dominant species. Both the instantaneous growth rate and daily specific growth rate were comparable to those in the southern East China Sea, which is the main spawning and nursery ground of the species. Our data strongly suggest that the northern Satsunan area has favorable conditions for sustaining high larval population densities, even during phases with high population numbers. Our results provide insights for the fisheries management for S. japonicus in the Japanese Pacific coastal area, especially during high-stock periods.

Ujung Perling Island, located in the Langsa City area, is a coastal area that is a place for marine life to find food (feeding ground) and do spawning (nursery ground). This research was carried out in June 2020 in the waters of the Ujung Perling island. The research method used is descriptive exploratory. The data collection point is divided into 4 stations, each station is taken 3 times in the morning, afternoon and evening. Water quality data retrieval, namely pH, temperature, and dissolved oxygen using a multichecker parameter, depth and brightness using a secchi disk, and salinity using a refractometer. Data collection for all parameters with a frequency of once a week for 1 month. The results of this research are the water temperature ranges from 27–30ºC, salinity ranges from 30.1–32 ppt, depth ranges from 0.5–5 m, pH 7–8.1, and DO 5.1–8.2 mg/ L. [ABSTRACT FROM AUTHOR]

Understanding the structure and richness of natural communities is a fundamental goal of marine ecology, and foundation species such as large macroalgae have a disproportionate role in structuring biodiversity. However, high-resolution information on assemblages associated with macroalgae is lacking for many species and regions. Saccorhiza polyschides is a warm-temperate kelp with a relatively short lifespan (12–18 months), large thallus and bulbous holdfast offering habitat for diverse assemblages. In the UK, S. polyschides populations are thought to have proliferated recently. Here, we quantified the density and habitat structure provided by S. polyschides along a gradient of wave exposure within Plymouth Sound, and examined the composition and diversity of associated faunal assemblages. Density varied significantly between sites but not by wave exposure, while biometric measurements were generally highly variable. Senescing holdfasts from sporophytes offered valuable habitat, with high abundance and richness of associated assemblages, although these varied markedly between sporophytes and sites. Faunal abundance, taxon richness and diversity were significantly higher at fully exposed sites than at moderately exposed sites. Internal volume of holdfasts was positively correlated with faunal abundance and taxon richness. We recorded more than 27 distinct taxa and up to ~600 individuals within a single holdfast. Taxa included three fish species, including a novel observation of the pipefish Nerophis lumbriciformis. Further work is needed to examine seasonality in habitat structure and associated diversity patterns but our study demonstrates that even remnant holdfasts from decaying sporophytes represent a valuable microhabitat that may provide shelter, protection and food during winter. [ABSTRACT FROM AUTHOR]

The seasonal occurrence and temporal sexual segregation of great white sharks Carcharodon carcharias have been widely documented in various temperate and sub-tropical waters across the globe. Yet, there is limited understanding of the relationship between the life stages and habitat use of C. carcharias, particularly in the Southern Cape. In this study, we investigated the population dynamics of C. carcharias in Mossel Bay, South Africa, between 2009 and 2013, using skipper logbooks and citizen research data obtained by a cage-diving vessel. A total of 3064 sharks, ranging in life history stages from young-of-the-year to subadult, were sighted during 573 trips. Juveniles dominated the sightings throughout the study, and there was marked sexual segregation, with females dominating the total sightings of sharks. C. carcharias were most abundant during the cooler, winter season, with females differing in abundance seasonally and males maintaining a low abundance throughout the year but peaking in the winter. In addition, sea surface temperature was the best indicator of C. carcharias presence. Abundance was greatest when vertical water visibility exceeded 3 m, with cloud cover influencing overall abundance negatively. Likely reasoning for the aggregation of C. carcharias in Mossel Bay includes the favourable conditions and abundance of food. Juvenile sharks may also utilise this area as a training ground to learn from larger conspecifics. This research demonstrates that information on population size and structure of C. carcharias can be obtained effectively through a compilation of logbook and citizen science data to assess and identify potential critical habitats in the quest to develop appropriate management strategies. This research also shows value in commercial cage-diving operations deriving international data sets needed to assess global populations of C. carcharias. [ABSTRACT FROM AUTHOR]

Southern right whales in south‐eastern Australia are endangered and vulnerable to impacts from human disturbance. Information on population demographics and movement data is needed to inform ongoing species management. While the number of whales observed using the south‐eastern Australian coastline is increasing, there has been no change over three decades in the annual abundance of cow‐calf pairs at Logans Beach in Warrnambool, Victoria, the only established calving ground in south‐east Australia. Knowledge of life history parameters of the south‐eastern Australian subpopulation is lacking. Here, we examine sightings and photo‐identification data from southern Australia to investigate calving intervals, long range movements and fidelity to the Logans Beach calving ground. Sightings data revealed at least 93 calves were born at Logans Beach between 1980 and 2018 (an average of 2.6 per year) with a mean calving interval of 3.5 ± 0.2 years (± SE, n = 34). Comparison between photo‐identification catalogues compiled for south‐eastern and south‐western Australia shows that southern right whales are wide ranging within southern Australian waters. Females can be sighted at locations as far apart as 3,800km across seasons with at least 7% of whales using both regions. We also provide the first report of an Australian southern right whale female belonging to one subpopulation relocating long‐term to a calving area in another. This work highlights knowledge gaps for the south‐east Australian subpopulation such as the proportion of female calves born at Logans Beach returning to their natal site and the degree of mixing between the two Australian subpopulations outside their wintering areas. Our work provides the first assessment of calving rates, movement and site fidelity within the south‐eastern Australian subpopulation, critical for understanding constraints to recovery and informing conservation management of southern right whales in Australia. Targeted, long‐term monitoring programs across south‐eastern Australia are needed to provide demographic information on which to base assessments of the impacts of anthropogenic threats such as noise disturbance, entanglement and vessel strike. [ABSTRACT FROM AUTHOR]

Brachyuran crabs are an important ecological and economical, yet often unstudied aspect of intertidal mudflats of the Arabian Peninsula. Here we provide baseline density estimates of crabs at the relatively pristine intertidal mudflats of Barr Al Hikman (Sultanate of Oman) and provide information on their life cycle and habitat preference. Across the winters of 2012–2015 crabs were sampled on a grid covering the entire intertidal depth gradient. 29 species were found and average densities varied between 12 and 54 crabs/m2. Deposit-feeding and herbivorous crabs were the most abundant species across all winters. Size frequency data and the presence of ovigerous females show that most crabs species reproduce in the intertidal area. P. segnis, the most important crab for local fisheries, was found to use the intertidal area as a nursery ground. We analysed the relationships between the two most abundant crab species, Macrophthalmus sulcatus and Thalamita poissonii and the environmental variables: seagrass density, tidal elevation, median grain size and sediment depth using Random Forest models. The predictive capacity of the models and the relative importance of the environmental predictors varied between years, but crab densities in general were positively associated with seagrass density, presumably because seagrass offers feeding habitat. [ABSTRACT FROM AUTHOR]

The limitations imposed by traditional sampling methods have restricted the acquisition of data on key fisheries parameters. This is particularly the case for juveniles because most traditional gear explicitly avoids the capture of juveniles, and the juveniles of many species use habitats in which traditional gear is ineffective. The increasing availability and sophistication of Remote Underwater Video Techniques (RUVs) such as Baited Remote Underwater Video, Unbaited Remote Underwater Video and Remotely Operated Underwater Vehicles offer the opportunity of overcoming some of the key limitations of more traditional approaches. However, RUV techniques come with their own set of limitations that need to be addressed before they can fully realize their potential to shed new light on the early life history of fish. We evaluate key strengths and limitations of RUV techniques, and how these can be overcome, in particular by employing bespoke computer vision Artificial Intelligence approaches, such as Deep Learning in its Convolutional Neural Networks instantiation. In addition, we investigate residual issues that remain to be solved despite the advances made possible by new technology, and the role of explicitly identifying and evaluating key residual assumptions. [ABSTRACT FROM AUTHOR]

Soft-substrate tide pools are considered important habitats for fishes from an ecological perspective. However, the ecological roles of such pools and use patterns by fish remain unclear, especially regarding differences between estuarine and coastal tidal flats. In this study, quantitative sampling using the quadrat method was performed in the estuarine and coastal tidal flats on Okinawa-jima Island of subtropical Japan during four seasons. Ecological roles of soft-substrate tide pools were classified as follows: (1) permanent habitat for residents; (2) nursery ground for transients; and (3) waiting area until high tide for accidental species. Within these classifications, the ecological role and value of tide pools for transient fishes varied between the tidal flat types. The habitat value of tide pools is higher for residents than for transient species because the habitat is not replaceable for residents because of their specific ability to survive there. By contrast, transient and accidental species use the tide pools as temporary habitats; however, their high diversity affects the variation in community structure on Okinawa-jima Island. Our results suggest that we should consider not only species diversity, but also habitat use patterns of individual species, together with their life history, when evaluating habitat value with regard to conservation and management of each tidal flat. This study revealed differences in the ecological role of soft-substrate tide pools between estuary and coastal tidal flats. The different types of tidal flat play different roles for groups of transient species, but similar roles for residents. Accordingly, we should consider not only species diversity, but also habitat use patterns of individual species through their life history when evaluating habitat value. [ABSTRACT FROM AUTHOR]

Between 1 July 2008 and 14 April 2018, five young-of-the-year (YOY) (TL range 85-175 cm) and six juvenile (TL range 180-300 cm) white sharks (Carcharodon carcharias) were caught off the Turkish coast of the Aegean Sea. The mean length + standard deviation of YOY and juvenile white sharks were 138.1+34 cm and 206.6+46 cm, respectively. The YOY white sharks were caught only in Edremit Bay and juveniles were captured in several localities outside of the mentioned region. Based on the findings of previous studies, it is suggested that Edremit Bay may serve as a nursery ground for C. carcharias in the northern Aegean Sea and the surrounding insular marine area outside of the bay waters, may serve as a growing and feeding ground for juveniles until maturity. The white shark population in the Mediterranean may be considered at greater risk of local extirpations than previously thought, and effective management of Edremit Bay as a nursery ground is crucial regarding the overall survival of white sharks in the Mediterranean. [ABSTRACT FROM AUTHOR]

While otolith shape analysis can provide a valuable tool for discriminating between fish populations, factors which may influence otolith shape, such as the effect of size, directional asymmetry in growth, and local environmental conditions, are often unknown. Here, we analyzed differences in otolith shape across three size classes of age-0 common sole Solea solea L. from nursery grounds off the Belgian coast and in the Wadden Sea. Across size classes, form-factor decreased and roundness remained consistently high in both nursery grounds, while ellipticity increased in the Belgian nursery. Directional asymmetry between left and right otoliths measured by Fourier coefficients accounted for 0.96 and 7.2% of the variance when comparing otoliths overall, and for each size class, respectively. Within the Belgian nursery, results were consistent across sampling years and locations. In addition, otolith shape was marginally different between nursery grounds, but highly variable within nursery grounds. A small divergent group, which seems partly related to fish size, was noted at both spatial and temporal scales. Based on these results and before embarking on a study of population structure using otolith shape in age-0 common sole, we recommend testing for directional asymmetry and fish size effects across the entire region of interest. [ABSTRACT FROM AUTHOR]

Acanthopagruslatus and A.schlegelii (Sparidae) are closely related species distributed in northern tropical to temperate coastal waters of eastern Asia. Early life histories of the two species were investigated by seine net sampling in the Tien Yen estuary, northern Vietnam, which is probably the southernmost co-occurrence locality for these species. In northern Vietnam, early juveniles of both the Acanthopagrus species occurred in the Tien Yen estuary from December to March (A.schlegelii) or December to April (A.latus) when temperatures ranged from ca. 16 to 25 °C. The given temperature range is observed twice (spring and autumn) a year in Japan, and A.latus and A.schlegelii early juveniles are abundant respectively in each season. Thus, a thermoperiodicity of early juveniles of the two Acanthopagrus is common Asia-wide. The two species occurred as the same developmental stage, being markedly more abundant and having larger sizes in A.latus. The Acanthopagrus early juveniles inhabited bank waters of the estuary. Although waters continued to be mixed horizontally by temperatures but to be stratified by salinities during the study period, there was little variation in developmental stage and size among stations for both species. The two Acanthopagrus species from Vietnam spawn for the same season and their early juveniles simultaneously use the same nursery ground. [ABSTRACT FROM AUTHOR]

We investigated the effect of feeding habits on the fatness (length–weight relationship (LW)) and otolith growth of age‐0 Pacific bluefin tuna (PBF) (fork length (FL) of 15.0–29.9 cm) collected off the southwestern Pacific coast of Japan from July to August during 2010–2015. The feeding rate on Clupeiformes (FRc) was substantially influenced by the path of the Kuroshio Current during early summer. We suggest that the following patterns occurred in the feeding habits of PBF. In 2012 and 2014, the short distance from the coast to the Kuroshio provided high overlap between PBF and Clupeiformes and increased the opportunity for feeding, and this pattern likely caused the observed diet shift from Crustacea to Clupeiformes by smaller PBF in the studied years than those in other years. In 2011 and 2015, the encounter probability for Clupeiformes might have been low due to the long distance to the Kuroshio Current, which led PBF to actively consume non‐Clupeiformes Teleostei. In contrast, in August 2010 and 2015, PBF did not encounter Clupeiformes or other Teleostei and may have been forced to feed on a large number of Crustacea; this effect was likely due to high water temperatures. Despite the interannual fluctuation in the timing of the diet shift and the feeding intensity (FI), these factors did not contribute to growth in length; rather, they contributed to fatness. Considering size‐dependent mortality in the larval stage, these results suggest that only fast‐growing individuals survive, even if the feeding conditions drastically change. [ABSTRACT FROM AUTHOR]

This study investigates the trophic diversity of fishes living in a meadow of Caulerpa prolifera on a bimonthly basis between May 2006 and April 2007 in a semi-enclosed coastal marine ecosystem of the Mediterranean Sea (Elounda Bay, Crete Island). The study area is shallow and protected from waves, and it is covered by a C. prolifera bed, characterized by high organic input and a highly diverse macrobenthic community. Feeding patterns of the fish, investigated on the basis of stomach content analyses, were described in terms of numerical abundance and frequency of occurrence of prey taxa. A total of 1642 fish individuals, belonging to 17 species, were examined. In total, 45,674 prey individuals were identified belonging to 110 prey taxa, most of which were Malacostraca including their larvae and Copepoda (41,175 individuals identified to 71 taxa). Four different trophic groups were identified: herbivorous, pelagic, benthic (hyperbenthic) and piscivorous. Trophic diversity patterns of the fish species studied were also compared to the relative availability of macrobenthic and zooplanktonic taxa during the same period in the study area. The coexistence of many different, mostly benthic but also pelagic, fishes and their juveniles implies their high trophic flexibility, which is probably important for their survival in this particular habitat. Results of the present study provide basic knowledge on trophic diversity and interactions in the marine ecosystem and, therefore, some evidence as to the protection value of this particular habitat, which is essential for the implementation of a multispecies approach to decision-makers and managers of fisheries sources of the region.

The movement of fish eggs and larvae in bay and estuarine systems is affected by freshwater discharge. In this study, the assemblage structures of ichthyoplankton eggs and larvae were assessed for the first time in Jinju Bay, South Korea, to identify the spawning and nursery functions of the bay. Fish eggs and larvae and several environmental parameters were sampled monthly from April 2015 to March 2016 inside and outside of the bay. Within the bay we collected eggs and larvae from 25 and 35 species, respectively, indicating greater diversity than outside the bay, where we collected eggs and larvae of 20 and 28 species, respectively. Fluctuations in water temperature and salinity were larger inside than outside of the bay, and chlorophyll-a concentration was higher within the bay, likely due to discharge from the Namgang Dam, which causes water to flow from the inside to the outside of the bay. This process influences fish larva abundance, such that more larvae are found outside than inside the bay. We also found that 28 fish species use Jinju Bay as a spawning ground. For some species, the timing of egg and larva appearance differed inside and outside of the bay, suggesting that the timing of spawning may differ between the two environments.

Abstract We conducted a laboratory experiment and field collections of juvenile marbled flounder (Pseudopleuronectes yokohamae) to assess growth rates of juveniles. In the laboratory, cultured juveniles of approximately 31 and 46 mm standard length grew fastest at 20 °C, while juveniles of approximately 21 mm grew faster at 12–14 °C than at 20 °C. This result confirmed that optimal temperature for growth of juveniles changes ontogenetically. Juveniles were also collected from shallow estuaries during April to May, during which the water temperature increased from 13 to 22 °C. The increase in optimal temperature is advantageous for juveniles, because both juvenile size and ambient temperature increase as the season progresses. Growth rates of juveniles were nearly maximum under given temperatures in the field when assessed from otolith microstructure. Thus, juveniles grow at high rates in the field, although ambient temperatures are not necessarily optimal for growth. Graphical abstract Unlabelled Image Highlights • Maximum growth rates of juvenile marbled flounder were examined in the laboratory. • Thermal optima increased from 12 to 14 °C to 20 °C with the size increase of juveniles. • Juveniles were collected in the field until May with temperatures below 20 °C. • In situ growth rates of juveniles were evaluated to be nearly maximum. [ABSTRACT FROM AUTHOR]

Silver-biddy (Gerreidae: Gerres) are commercially important euryhaline fishes in coastal waters; however, information about their distribution during early stages in estuarine environments is poorly known. The present study aims to elucidate the habitat utilization of two species of the family, Gerres japonicus and G. limbatus as larvae and juveniles based on monthly collections from 2013 to 2015 in the Tien Yen estuary, northern Vietnam. They occurred from April to June for G. japonicus and in April and May for G. limbatus with a peak in May for both the species. Both G. japonicus and G. limbatus used the Tien Yen estuary as a nursery ground; however, the former species that colonized the shallows along the banks of the estuary extended to near freshwater habitat, whereas the latter was found at the end of the upper reach and the middle reach. The different habitat uses between the two species in the early life history may be related to their specific salinity preference as G. japonicus prefer lower salinities than G. limbatus. [ABSTRACT FROM AUTHOR]

Batoid chondrichthyans are vulnerable to commercial fisheries even though they are often not targeted. A greater understanding of their reproductive biology is important to facilitate their conservation. In February 2013, 89 female and 40 male Lusitanian cownose ray (Rhinoptera marginata) specimens were accidentally caught in Mersin Bay in the eastern Mediterranean Sea. Thirty-six fish were gravid, each bearing one embryo. Of the remaining females, 39 were sexually mature but not gravid and 14 were immature. There were 28 mature and 12 immature males. The average disc width (DW) of both mature females (80.2 cm) and males (74.2 cm) was significantly higher than that of immature females (60.7 cm) and males (60.3 cm). For all rays, DW and total weight (TW) were in the range 55.7-98.2 cm and 1802-13 600 g. The DW and TW measured for all 16 female and 20 male embryos were in the range 15.6-29.2 cm and 57-281 g. Such a large single haul sample, including many gravid specimens and mature males, indicates a schooling formation at capture. The location in Mersin Bay near the estuaries of the Tarsus and Seyhan rivers, and its relative closeness to the sampling location of a previously reported neonate, suggests that this region may be a nursery area for Lusitanian cownose rays in the eastern Mediterranean. [ABSTRACT FROM AUTHOR]

Despite its worldwide distribution and vulnerable status, knowledge on the biology and ecology of the smooth hammerhead Sphyrna zygaena in the temperate NE Atlantic is very scarce. Here, we reveal intra-annual fluctuations in S. zygaena abundance in the Portuguese southwestern coast, using sightings data collected on board whale watching boats over five years (2010-14; excluding winter months). Moreover, we investigated how shark abundance is related to local environmental conditions. We describe the first smooth hammerhead “hotspot” in the NE Atlantic, and we show a recurrent pattern of occurrence during the warmer summer and autumn months (from July to October) near Sagres and Martinhal Bay and islands. Intra-annual variations in abundance were significantly associated with sea surface temperature and negatively related with upwelling index and chlorophyll a, suggesting horizontal movements linked to the seasonal changes. Hence, hammerheads moved inshore during the warmer periods (with low primary productivity), due to either direct influence of temperature in their movements or indirect influence in prey distribution. This hammerhead “hotspot” may constitute a nursery ground for S. zygaena, nevertheless, our data does not allow us to prove or refute such claim. Future telemetry-based studies should be conducted to fully understand hammerhead movements and habitat preferences, and to evaluate this “hotspot” as a critical habitat for this predator. [ABSTRACT FROM AUTHOR]

This study aimed to assess the diel changes of ichthyoplankton occurrence, during a known recruitment period, to a wind-dominated coastal lagoon (Argentina). We collected plankton samples at three sites of the lagoon's inlet area every 3 h during four 24 h cycles in mid austral summer. For each early-life history stage (eggs, yolk sac, preflexion larvae, postflexion larvae and early juveniles), the relationship between the abundance and possible combinations of the time of sampling, the wind effect, the wave period and the tidal state was evaluated by fitting generalized linear mix-effects models (GLMM). The wind effects depending on the time of sampling mainly affected fish abundance in all developmental stages. Overall, the highest abundances were collected at nocturnal hours when low-speed offshore winds blew. In addition, higher abundances of eggs, yolk sac and preflexion larvae were related to the incoming flood tide; whereas higher abundances of postflexion larvae and early juveniles were related to longer wave periods. We argued that the daily variation in the abundance of early-life history stages of fishes is related to the sea-land breeze cycle. Therefore, a conceptual framework of the recruitment process of eggs, larvae and early juveniles of fishes into this estuarine system considering the daily effect of winds is proposed. [ABSTRACT FROM AUTHOR]

The horizontal distribution of the early life stages of small yellow croaker Larimichthys polyactis in the Yangtze River estuary and its adjacent area was investigated through six ichthyoplankton surveys conducted during the period of mid-April to mid-July 2015. A total of seven eggs and 2461 larvae and juveniles of small yellow croaker were collected. Abundance of the specimens was highest in mid-May and lowest in mid-July. The composition of the different development stages of small yellow croaker varied among the six cruises, although post-flexion larvae and juveniles dominated the ichthyoplankton collection in each cruise. Specimens at different development stages showed different distribution patterns in the study area. The eggs, yolk-sac and pre-flexion larvae were mainly collected at stations with depth exceeding 30 m, while post-flexion larvae and juveniles were mainly distributed in the relatively shallow waters near to the mouth of the Yangtze River. In conclusion, the study suggested that the study area had largely lost the ecological function to support small yellow croaker spawning, although it could still serve as nursery ground for the species. [ABSTRACT FROM AUTHOR]

Observations (1978–1991) of distributions of pelagic juvenile Northeast Arctic cod (Gadus morhua L.) show that up to 1/3 of the year class are dispersed off the continental shelf and into the deep Norwegian Sea while on the way from the spring-spawning areas along the Norwegian coast to the autumn-settlement areas in the Barents Sea. The fate of this variable fraction of pelagic juveniles off-shelf has been an open question ever since Johan Hjort's (1914) seminal work. We have examined both the mechanisms causing offspring off-shelf transport, and their subsequent destiny using an individual-based biophysical model applied to quantify growth and dispersal. Our results show, consistently with the observations, that total off-shelf transport is highly variable between years and may be up to 27.4%. Offspring from spawning grounds around Lofoten have a higher chance of being displaced off the shelf. The off-shelf transport is dominated by episodic events where frequencies and dates vary between years. Northeasterly wind conditions over a 3–7-day period prior to the off-shelf events are a good proxy for dispersal of offspring off the shelf. Offspring transported into the open ocean are on average carried along three following routes: back onto the adjacent eastern shelves and into the Barents Sea (36.9%), recirculating within the Lofoten Basin (60.7%), or drifting northwest to the northeast Greenland shelf (2.4%). For the latter fraction the transport may exceed 12% depending on year. Recent investigations have discovered distributions of young cod on the northeast Greenland shelf indicating that conditions may support survival for Northeast Arctic cod offspring.

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This work aims to study the importance of mangrove area as nursery grounds for the juvenile of reef fishes in the Red Sea. Juvenile fishes were collected during three seasons in 2010 from three mangrove swamps by a beach seine net. The net was dragged on the bottom for 100 m three times. A total of 269 juvenile fishes were collected, representing 21 species in 19 families. The most abundant species formed about 86% of all collected fishes. Nine species were collected for the first time from mangrove areas in the Egyptian Red Sea. Most of the collected fishes are economically important fishes. Moreover, eleven families were belonging to coral reef fishes. The highest species richness value was recorded in Hamata mangroves. This finding showed that how mangroves could support the life history of many coral reef fishes.

The stony coral Cladocora caespitosa (Linnaeus, 1767) is an important Mediterranean habitat builder, whose survival is now being threatened by human activities and possibly natural events such as mass mortality and bleaching. We characterized the mollusc assemblage associated with colonies in the Gulf of Trieste (northern Adriatic Sea) and then tested whether the number of mollusc species increases in relation with colony size, following a Species-Area Relationship (SAR) model. At least 62 taxa were found in association with coral colonies, with bivalves constituting the dominant group. More than half of the 3034 specimens encountered were juveniles. Mollusc taxa richness increased with increasing C. caespitosa colony size according to the power-function model, whilst the analyses of trophic and functional groups supports the hypothesis of at least two factors underlying SAR (area per se and habitat diversity). Our results confirmed the importance of C. caespitosa for benthic communities, indicating that larger colonies support higher biodiversity, and suggesting that C. caespitosa is the most important habit builder among Mediterranean cnidarians, having also an influential function as a natural nursery ground. These results underline the necessity of new investigations aimed at filling gaps in our knowledge and planning new measures to protect the species. [ABSTRACT FROM AUTHOR]

The size and shape of a habitat patch can influence patterns of species utilisation. The present study examined how the width of fringing mangrove habitats affects the composition and use patterns of the fish assemblage using mangrove edge habitats on the flooding tide. Underwater cameras surveyed fish approaching mangrove habitats, ranging from a thin fringe 5 m wide to forests over 75 m wide, in a highly modified tropical estuary. The fish assemblage composition was similar across all mangrove widths, although the temporal patterns of use varied among mangrove widths for some species. The mean maximum number of individuals in the field of view was similar among mangrove widths, but fish were visible for a significantly greater proportion of time in videos from narrow (,20 m) than wide (≥20 m) mangrove stands (15 v. 3% respectively). At least some fish were visible in the field of view in narrow mangrove fringes throughout the first hour of the flood tide, whereas in wide mangroves areas the presence of fish declined over time. The findings suggest that estuarine fish are using mangrove edge habitat regardless of width, making narrow mangroves viable habitats for estuarine fish. [ABSTRACT FROM AUTHOR]

Current study was carried out to provide a better understanding on spatial and temporal variations in the phytoplankton community structure in Marudu Bay, an important nursery ground for fishery resources within the Tun Mustapha Marine Park and Coral Triangle Initiative, and their relationship with environmental variables. Samplings were conducted monthly from April 2014 to April 2015 in Marudu Bay, Malaysia. Water samples were collected for nutrients analysis, zooplankton and phytoplankton counting. Moreover, the in situ environmental parameters were also examined. The field study showed a total of forty seven phytoplankton genera, representative of 33 families were identified. The nutrient concentrations in Marudu Bay was low (mesotrophic) throughout the year, where the phytoplankton community was often dominated by Chaetoceros spp. and Bacteriastrum spp. In general, increase in nitrate concentration triggered the bloom of centric diatom, Chaetoceros spp. and Bacteriastrum spp. in Marudu Bay. However, the bloom of these phytoplankton taxa did not occur in the presence of high ammonia concentration. In addition, high abundance of zooplankton also a limiting factor of the phytoplankton blooms particularly at end of southwest monsoon. High silica concentration promoted the growth of pennate diatoms, Proboscia spp. and Thallassionema spp., but the depletion of silica quickly terminated the bloom. Interestingly, our study showed that Chaetoceros spp., tolerated silica depletion condition, but the average cell size of this taxon reduced significantly. In summary, the phytoplankton community structure in mesotrophic environment is more sensitive to the changes in zooplankton abundance, nutrient concentration and its ratio than that in nutrient rich environments. This study also recommends that bivalve farming at industrial scale is not recommended in Marudu Bay because it potentially depletes the primary productivity hence jeopardizing the availability of live food for larvae of many natural fishery resources in the bay. [ABSTRACT FROM AUTHOR]

The impact of the great tsunami, which was generated by the Great East Japan Earthquake on 11 March 2011, on the quality of a nursery ground for juvenile Japanese flounder Paralichthys olivaceus with a sandy bottom of <15 m in depth in Sendai Bay, Japan, was evaluated. Growth rates of juveniles, as an index of the quality of the nursery ground, were compared between before and after the tsunami. Recent growth rates ( RGR; mm day−1) between 1 and 6 days before collection in 2011-2013, which were estimated from the width of otolith increments, ranged from 0.84 to 2.37 mm day−1 for juveniles of 24.8-146 mm in total length ( TL). These figures are comparable to the maximum RGR for juvenile Japanese flounder in the literature. A linear model for RGR selected TL and bottom temperature but rejected biomass of the mysid Orientomysis mitsukurii, the main prey item, as explanatory variables, indicating that the growth rates of juveniles after the tsunami were not controlled by food density, i.e., optimal food condition occurred in the nursery. A linear model for observed growth rate (mm day−1), which was calculated from the temporal changes in the juvenile size frequency distribution, suggested the growth rate did not change between before and after the tsunami. Additional information on prey abundance and sediment size distribution also support this conclusion. Therefore, we conclude that the quality of the nursery ground for juvenile Japanese flounder in the study site has not been damaged by the great tsunami. [ABSTRACT FROM AUTHOR]

Background: Although the effort in the study of white sharks in Mexico is rapidly elucidating adult biology, almost nothing is known about the juveniles. Current understanding of this life history is based largely on the incidental take of juveniles in nursery grounds in the Pacific coast of Baja California and some individuals tagged in the USA that have migrated to Mexican waters. Also, it is not known how or when they recruit to adult aggregation sites or how they learn to make seasonal migrations offshore. Five white sharks were manually tracked using ultrasonic transmitters with depth and temperature sensors between 2006 and 2007. Additional white sharks were tagged (N = 60) with long-lived coded transmitters and detected at listening stations located on the west coast of the United States of America and Guadalupe Island (GI) from August 2008 to October 2015. Results: We found that: (1) juvenile white sharks remained close to the island throughout the day between the surface and 50 m depth in warm waters (from 14 to 20 °C), whereas the adults moved offshore into deep waters during the day and stayed close to the island during the night presenting a broader tolerance of colder waters (from 9 to 20 °C); (2) tagged white sharks had a positive correlation between total length and habitat range, and the core areas of adults were related to pinniped colonies; (3) adults patrolled in deep waters in November and December when the northern elephant seals (NESs) returned back to the island for pupping with their mean mass higher than during the winter post-breeding migration; (4) tagged juvenile white sharks remained near the island for 12-14 months before departing; and (5) tagged subadults undertook coastal migrations before starting their offshore migrations. Conclusions: The data collected in our study suggest that white shark juveniles arrive to GI from nursery grounds on the mainland after they have reached at least 180 cm TL; then, they remained around the island for several months, potentially taking advantage of the diversity of prey. In addition, they may start their first offshore migrations, coming back to their nursery grounds and GI before they reach maturity, while at GI juveniles stayed close to the shore and in shallow water to avoid adults, probably feeding on demersal prey and species that perform nocturnal migrations such as squid and mackerel. It is argued that the distribution of the large white sharks in GI is controlled by the availability of NES and that adult white sharks look for this prey in deep waters during the day in the vicinity of the seal colonies, taking advantage of the great visibility of GI waters. It is also possible that white sharks take advantage of NES in GI before they go to their pupping grounds to give birth in California and Baja California or to their offshore migration to the west. [ABSTRACT FROM AUTHOR]

Daily growth rates were estimated from larval anchovy (Engraulis encrasicolus) sampled in their main nursery grounds off the Bay of Málaga (SW Mediterranean) during the 2000 and 2001 spawning seasons. Significantly higher growth rates were observed in the 2001 larval population, representing a 20% increase through the larval size classes analysed. The decimated SW Mediterranean anchovy population experienced a successful anchovy recruitment during this year estimated at 13,000 tons for the Bay of Málaga by the acoustic evaluation of small pelagic resources. The size distribution of the recruited anchovy juveniles during 2000 and 2001 showed an increase of approximately 2 cm. Their corresponding anchovy spawning seasonality agrees with the estimates from the growth model fits of each year. Data on the environmental background for the two years sampled are provided by a historical quarterly monitoring project. Zooplankton showed a two-fold significant increase during July 2001, coastwise as well as offshore. No significant changes in surface temperature were observed between years. Instead of the usual summer spawning peak, anchovy peak spawning shifted towards early spring during the 2001 spawning season. The study provides evidence from field data on the relationships of larval growth variability and recruitment.

Intertidal habitats are only available to most nekton when inundated by tides. We assessed the variability of access to mangrove habitats for aquatic organisms over 3500 km of Australia's east coast. After determining the elevation of the lower mangrove edge across 19 locations, we used 6 years of historic hourly tide gauge readings to estimate wetland edge flooding frequency, duration, and depth at each location. Although mangrove edges broadly tracked mean sea level along the east coast, deviations in edge elevation corresponded to substantial geographic variation in flooding dynamics. Mangrove edges were flooded from as little as 20% of the time in central Queensland sites, to as much as 90% of the time during some seasons in northern New South Wales. Flooding frequency and depth were also highly variable, with some mangrove edges flooding and draining almost twice as frequently as others. Flooding depth profiles revealed dynamic patterns of flooding of mangrove habitat. The variability in flooding dynamics demonstrates that the availability of mangrove habitat to aquatic organisms varies significantly among locations. This variability in flooding patterns suggests the nature of mangrove use and the functional value of these habitats for fishes and nektonic crustaceans may differ substantially among regions. [ABSTRACT FROM AUTHOR]

Coastal ecosystems, such as estuaries, salt marshes, mangroves and seagrass meadows, comprise some of the world's most productive and ecologically significant ecosystems. Currently, the predominant factor considered in valuing coastal wetlands as fish habitats is the contribution they make to offshore, adult fish stocks via ontogenetic migrations. However, the true value of coastal nurseries for fish is much more extensive, involving several additional, fundamentally important ecosystem processes. Overlooking these broader aspects when identifying and valuing habitats risks suboptimal conservation outcomes, especially given the intense competing human pressures on coastlines and the likelihood that protection will have to be focussed on specific locations rather than across broad sweeps of individual habitat types. We describe 10 key components of nursery habitat value grouped into three types: (1) connectivity and population dynamics (includes connectivity, ontogenetic migration and seascape migration), (2) ecological and ecophysiological factors (includes ecotone effects, ecophysiological factors, food/predation trade-offs and food webs) and (3) resource dynamics (includes resource availability, ontogenetic diet shifts and allochthonous inputs). By accounting for ecosystem complexities and spatial and temporal variation, these additional components offer a more comprehensive account of habitat value. We explicitly identify research needs and methods to support a broader assessment of nursery habitat value. We also explain how, by better synthesising results from existing research, some of the seemingly complex aspects of this broader view can be addressed efficiently. [ABSTRACT FROM AUTHOR]

Abstract: This work aims to study the importance of mangrove area as nursery grounds for the juvenile of reef fishes in the Red Sea. Juvenile fishes were collected during three seasons in 2010 from three mangrove swamps by a beach seine net. The net was dragged on the bottom for 100m three times. A total of 269 juvenile fishes were collected, representing 21 species in 19 families. The most abundant species formed about 86% of all collected fishes. Nine species were collected for the first time from mangrove areas in the Egyptian Red Sea. Most of the collected fishes are economically important fishes. Moreover, eleven families were belonging to coral reef fishes. The highest species richness value was recorded in Hamata mangroves. This finding showed that how mangroves could support the life history of many coral reef fishes. [Copyright &y& Elsevier]

Abstract: Essential fish habitat suitability (EFHS) models and geographic information system (GIS) were combined to describe nursery habitats for three flatfish species (Solea solea, Pleuronectes platessa, Dicologlossa cuneata) in the Bay of Biscay (Western Europe), using physical parameters known or suspected to influence juvenile flatfish spatial distribution and density (i.e. bathymetry, sediment, estuarine influence and wave exposure). The effects of habitat features on juvenile distribution were first calculated from EFHS models, used to identify the habitats in which juvenile are concentrated. The EFHS model for S. solea confirmed previous findings regarding its preference for shallow soft bottom areas and provided new insights relating to the significant effect of wave exposure on nursery habitat suitability. The two other models extended these conclusions with some discrepancies among species related to their respective niches. Using a GIS, quantitative density maps were produced from EFHS models predictions. The respective areas of the different habitats were determined and their relative contributions (density × area) to the total amount of juveniles were calculated at the scale of stock management, in the Bay of Biscay. Shallow and muddy areas contributed to 70% of total juvenile relative abundance whereas only representing 16% of the coastal area, suggesting that they should be considered as essential habitats for these three flatfish species. For S. solea and P. platessa, wave exposure explained the propensity for sheltered areas, where concentration of juveniles was higher. Distribution maps of P. platessa and D. cuneata juveniles also revealed opposite spatial and temporal trends which were explained by the respective biogeographical distributions of these two species, close to their southern and northern limit respectively, and by their responses to hydroclimatic trends. [Copyright &y& Elsevier]