Coastal Nursery Areas Research Articles

Spatial and temporal variability in larval connectivity of North Sea plaice Pleuronectes platessa between spawning grounds and coastal European nurseries

Annual year-class strength in North Sea plaice Pleuronectes platessa Linnaeus, 1758 appears to be determined by the connectivity of eggs and larvae between open-sea spawning grounds and coastal nursery areas. Hydrodynamic modelling studies indicate that coastal nurseries can be supplied with larvae from multiple offshore spawning locations. To verify this, we compared relative size-frequency distributions of demersal juvenile plaice just after larval immigration between coastal nurseries as a proxy for larval origin. During 12 yr, up to 21 stations in the Dutch coastal zone and international Wadden Sea were visited and sampled at the beginning of May at the end of larval immigration. The results of the size-frequency analysis showed 2 distinct clusters of stations. The first cluster included all stations along the Dutch coast and Wadden Sea up to Wangerooge in the German East Frisian Wadden Sea, most likely dominated by supply from spawning grounds in the Southern Bight, with contributions from the English Channel and the Dogger Bank. The second cluster included all stations in the North Frisian Wadden Sea, most likely supplied from spawning grounds in the German Bight and near the Dogger Bank. The higher interannual variability in the first cluster might be caused by a larger variability in the relative contributions from multiple spawning areas (English Channel, Southern Bight, Dogger Bank). The comparison of the relative size-frequency distributions at the end of larval immigration introduced in this study may also be a useful tool for the validation of connectivity modelling studies in other areas and for other species.

Spatial and temporal analysis of juvenile blacktip reef shark (Carcharhinus melanopterus) demographies identifies critical habitats.

Reef shark species have undergone sharp declines in recent decades, as they inhabit coastal areas, making them an easy target in fisheries (i.e., sharks are exploited globally for their fins, meat, and liver oil) and exposing them to other threats (e.g., being part of by-catch, pollution, and climate change). Reef sharks play a critical role in coral reef ecosystems, where they control populations of smaller predators and herbivorous fishes either directly via predation or indirectly via behavior, thus protecting biodiversity and preventing potential overgrazing of corals. The urgent need to conserve reef shark populations necessitates a multifaceted approach to policy at local, federal, and global levels. However, monitoring programmes to evaluate the efficiency of such policies are lacking due to the difficulty in repeatedly sampling free-ranging, wild shark populations. Over nine consecutive years, we monitored juveniles of the blacktip reef shark (Carcharhinus melanopterus) population around Moorea, French Polynesia, and within the largest shark sanctuary globally, to date. We investigated the roles of spatial (i.e., sampling sites) and temporal variables (i.e., sampling year, season, and month), water temperature, and interspecific competition on shark density across 10 coastal nursery areas. Juvenile C. melanopterus density was found to be stable over 9 years, which may highlight the effectiveness of local and likely federal policies. Two of the 10 nursery areas exhibited higher juvenile shark densities over time, which may have been related to changes in female reproductive behavior or changes in habitat type and resources. Water temperatures did not affect juvenile shark density over time as extreme temperatures proven lethal (i.e., 33°C) in juvenile C. melanopterus might have been tempered by daily variation. The proven efficiency of time-series datasets for reef sharks to identify critical habitats (having the highest juvenile shark densities over time) should be extended to other populations to significantly contribute to the conservation of reef shark species.

Sensitivity to life-history parameters in larval fish drift modelling predictions for contrasting climatic conditions

Many marine fish species display a long larval drift between offshore spawning grounds and coastal nursery areas. This drift, whose efficiency drive the renewal of the population, critically depends on many environmental factors and on the spawning behaviour of species. Given the complexity to collect field data on fishes early life stages, modelling has proved to be one of the most valuable tool to explore such questions. However, these complex models require many parameters, many of which are uncertain, making a comprehensive sensitivity analysis a crucial step before drawing conclusions on the effects of environmental drivers. This study focused on the larval drift of five species archetypes mimicking five commercially important fish species with contrasted spawning strategies and larval ecology, in five different sub regions over Western Europe, from the Iberian coast to the North Sea. Using an hydrodynamic model (MARS3D) coupled with an individual-based model, and by building a simulation design suitable for such sensitivity analysis, we assessed the relative influence of extrinsic (years and region’s hydrodynamics) and intrinsic (spawning grounds’ depth, spawning period, vertical migration, developmental rate, daily mortality and tolerance to temperature) factors and their two-ways interactions on recruitment success to nurseries. The thermal tolerance of species was one of the leading factors, suggesting that this is a critical parameter, especially when modelling species recruitment success at the edge of their distribution range. On the other hand, other parameters such as the nycthemeral vertical migration, that are often discussed in such larval drift simulation exercise, have proved to have a more limited influence for an analysis at such a large spatial scale. Overall, when studying larval drift on a large scale, local hydrodynamics and inter-annual variations hold most of the explained variance in the recruitment success, confirming the importance of repeating simulations over multiple years before exploring the connectivity among spawning and nursery areas.

Mediterranean juvenile white seabream rely on phytal fauna as primary food source in coastal nursery areas

Nursery areas are essential fish habitats due to their relevance in the survival of early stages of fish populations. They are also considered as of high priority in marine conservation strategies. Here, we investigated the diet of white seabream [Diplodussargus (Linnaeus, 1758)] settlers in six nursery areas located in the shallow waters of coves in Minorca Island (Balearic Islands, Spain). Our aim was to characterize the food sources at different stages of juvenile development and their site-related variability in order to discern the importance of trophic links in cove selection during settling. The gut contents of 101 juveniles captured at different coves, three to the north of the island (N), and three in the southern coast (S), revealed a marked preference for feeding on crustaceans and, in particular, on harpacticoid copepods (>90% of gut contents). Copepods represented the main food source (80 ±4.4%; mean ±S.E.) in younger seabream individuals (10 - 15 mm length). A higher diversity in prey items was observed in the larger size-classes (s2: 16 - 23 and S3: 24 - 30 mm, respectively), which incorporated other prey items such as amphipods, isopods, foraminiferans or ostracods. Diet composition did not vary between the two surveyed locations (North vs. South of the island), but it did show significant differences among the six coves (p<0.001). Comparison between cove sediment infaunal composition and gut contents revealed that predation on sediment communities was scarce. Instead, diet was typically of phytal origin. Our results highlight the importance of the algal component of shallow coastal areas as a foraging habitat. In particular, harpacticoid copepods were key for survival during early development phases. The potential use of harpacticoid copepods to track ontogenic shifts in habitat use by juvenile fish is discussed.

Genetic population dynamics of the critically endangered scalloped hammerhead shark (Sphyrna lewini) in the Eastern Tropical Pacific.

The scalloped hammerhead shark, Sphyrna lewini, is a Critically Endangered, migratory species known for its tendency to form iconic and visually spectacular large aggregations. Herein, we investigated the population genetic dynamics of the scalloped hammerhead across much of its distribution in the Eastern Tropical Pacific (ETP), ranging from Costa Rica to Ecuador, focusing on young-of-year animals from putative coastal nursery areas and adult females from seasonal aggregations that form in the northern Galápagos Islands. Nuclear microsatellites and partial mitochondrial control region sequences showed little evidence of population structure suggesting that scalloped hammerheads in this ETP region comprise a single genetic stock. Galápagos aggregations of adults were not comprised of related individuals, suggesting that kinship does not play a role in the formation of the repeated, annual gatherings at these remote offshore locations. Despite high levels of fisheries exploitation of this species in the ETP, the adult scalloped hammerheads here showed greater genetic diversity compared with adult conspecifics from other parts of the species' global distribution. A phylogeographic analysis of available, globally sourced, mitochondrial control region sequence data (n= 1818 sequences) revealed that scalloped hammerheads comprise three distinct matrilines corresponding to the three major world ocean basins, highlighting the need for conservation of these evolutionarily unique lineages. This study provides the first view of the genetic properties of a scalloped hammerhead aggregation, and the largest sample size-based investigation of population structure and phylogeography of this species in the ETP to date.

Association of early stage fishes with surf diatom Anaulus australis accumulations in a warm temperate surf zone, South Africa

Surf zones are recognised as important nursery habitats for early stage fishes worldwide, but microhabitat opportunities for feeding and refuge are not well studied. Surf diatoms accumulate in high densities, discolouring the water and offering potential refuge and feeding opportunities. The aim of this study was to investigate the association of early stage fishes with surf diatom Anaulus australis accumulations in the Sundays Beach surf zone on the South African southeast coast. Early stage fishes were sampled within and outside of visible A. australis accumulations using a 4.5 × 1.5 m larval fish seine net with 500 μm mesh. Over 22 sampling trips, 338 replicate samples were collected. Species diversity, the overall catch per unit effort (CPUE) and that of the dominant species Chelon richardsonii, Diplodus capensis, Rhabdosargus globiceps and R. holubi, were significantly higher within accumulations compared to outside. Postflexion larvae and early juveniles occurred in significantly higher numbers within accumulations, indicating that fishes were actively selecting A. australis accumulations. Generalized linear models revealed that temperature, dissolved oxygen (mg l−1), turbidity and A. australis biomass (μg Chl a l−1) were the most significant variables correlated with the overall CPUE and that of dominant species. Since A. australis accumulations have a patchy distribution in the surf zone, it is suggested that early stage fishes are opportunistically using this resource when and where it occurs as both a feeding and refuge area. Understanding the role of microhabitats for early stage fishes is essential for understanding survival and life history strategies within the mosaic of coastal nursery areas.

Trophic variation during the early stages of blacktip sharks (Carcharhinus limbatus) within coastal nurseries of the Galapagos Marine Reserve

The blacktip shark (Carcharhinus limbatus) is a placental shark that uses coastal nursery areas in the Galapagos Marine Reserve, where juveniles live during their early life stages. To better understand the feeding behavior of early juvenile blacktip sharks, we conducted stable isotope analysis on 57 samples from three coastal nurseries around the archipelago. We evaluated the intraspecific variation in trophic shifts of four size classes (<60, 60–69, 70–79 and ≥ 80 cm TL) based on δ13C and δ15N signatures. No significant differences in δ13C and δ15N values were observed among nursery areas (P = 0.127 and P = 0.736, respectively) nor between sexes (P = 0.881 and P = 0.993, respectively). However, there were significant differences among size classes, with δ13C and δ15N values showing a negative relationship with size (R = −0.54, P = 0.001 and R = −0.60, P = 0.001, respectively). Neonates (TL < 60 cm) exhibited a larger trophic niche, whereas larger individuals (TL ≥ 80 cm) exhibited a reduction in trophic niche as a result of different use of resources. Clustered δ15N signatures for the two largest size classes showed similar feeding patterns and same trophic level, while δ13C signatures in all size classes showed the use of several primary carbon sources. Our results showed trophic variations among early life stages, as a result of maternal reminiscence in neonates and foraging variation in larger size classes across coastal nursery areas. This is baseline information on the feeding behavior of early juvenile blacktip sharks in the Tropical Eastern Pacific.

Reduced Reproductive Success of Western Baltic Herring (Clupea harengus) as a Response to Warming Winters

Shallow estuaries, bays, and lagoons are generally considered hot spots of ocean productivity that often adjust rapidly to seasonal variations in atmospheric temperatures. During spring when biological reproductive processes begin in the temperate zones, regional climate variability can be immense and uncovering a non-linear biological response, such as fish recruitment to changing temperature regimes might be challenging. Using herring as a paradigm for a response of coastal spring productivity to regional climate drivers, we demonstrated how the annual timing of spawning periods can significantly affect the reproductive success of spring-spawning herring (Clupea harengus) in the western Baltic Sea. An investigation of spawning phenology in consecutive years indicated a temperature threshold range of 3.5–4.5°C triggering initial spawning in the coastal zone. Based on this finding, we analyzed the timing of larval hatching peaks, larval survival and recruitment to the adult population relative to multi-decadal time-series of seasonal sea-surface temperatures. The results revealed that the late seasonal onset of cold periods the corresponding elongation of the period where larvae hatch from the eggs and early larval hatching peaks significantly reduced larval production in a coastal nursery area and finally lead to a reduced abundance of juveniles in the entire distribution area. Using a combination of field research and time series analysis, we presented precedence for shifting regional winter regimes providing a present-day stressor to reproductive capacity of a central component of the coastal food web.

Effect of thermal and nutritional conditions on fatty acid metabolism and oxidative stress response in juvenile European sea bass (Dicentrarchus labrax)

Coastal nursery areas are subjected to a wide range of natural and anthropogenic stressors, including global warming, which indirectly influence trophic food webs. A global rarefaction of n-3 polyunsaturated fatty acids (PUFA) in trophic networks is in progress. The aim of this study was to assess the effect of a reduction in the dietary availability of n-3 PUFA on some molecular and biochemical parameters related to lipid metabolism and oxidative stress response in juvenile European sea bass (Dicentrarchus labrax) raised at two temperatures (15 °C and 20 °C). Fish were fed for five months with a reference diet (RD; 1.65% n-3 PUFA on a dry matter basis, DM), used as a proxy of trophic networks where n-3 PUFA is plentiful, and a lower n-3 PUFA diet (LD; 0.73% n-3 PUFA DM), designed to mimic a decrease in n-3 PUFA resulting from global changes (the n-3 PUFA levels tested remained above the nutritional minimum required for this species). Results showed that diet did not affect the hepatic expression of some mRNA coding for transcriptional factors involved in regulating the metabolic pathways related to fatty acid bioconversion. Although our molecular analysis was limited to transcript expression, these data suggest the presence of a threshold in the nutritional supply of PUFA above which the activation of these molecular pathways does not occur. However, the expression for most of the transcripts tested was up-regulated at 20 °C. Despite the high peroxidation index in fish fed RD, very few modifications of the oxidative stress response were associated with diet. At 20 °C, an increase of the enzymatic antioxidant response was observed, but there was no correlation with the peroxidation index or malondialdehyde products.

Recruitment variability in Baltic flounder (Platichthys solemdali) – effects of salinity with implications for stock development facing climate change

The brackish water Baltic Sea is strongly influenced by irregular saline water inflows. Fewer inflow events since the 1980s have resulted in a decrease in salinity, and will according to predicted climate change continue to decrease. The newly described Baltic flounder Platichthys solemdali has adapted to reproduction at low salinity conditions since it colonized the Baltic Sea 7000 years BP; in the area studied (ICES SD 3d 28.2) spawning occurs at 3–20 m depth at ca 7 psu. Here we monitored variability in year-class strength as newly settled 0-gr fish in three coastal nursery areas, and compared obtained recruitment indices with prevailing temperature and salinity conditions. 0-gr abundance indices varied considerably between years, from 1 to 90, 10–296 and 17–86 at the respective sampling site, and showed strong accordance with the age structure of the adult stock. Variability in temperature showed no effect, but stronger and weaker year-classes respectively were related to variability in salinity in the range 6.6–7.1 psu with stronger year-classes at >6.8 psu. This coincides with variability in spermatozoa motility, fertilization rates and early egg development at different salinities and suggests that the year-class strength may be set already at the egg stage. Thus, only small changes in salinity at spawning may affect reproductive success and ultimately stock development. The potential effects on stock abundance and distribution facing climate change call for changes in future fishing patterns as well as adaptations in management to prevent stock collapse.

Artisanal fishing activities and their documented interactions with juvenile white sharks inside a nursery area

Abstract Juvenile white sharks distribute in coastal nursery areas, which are essential for population growth. Bahía Sebastián Vizcaíno (BSV), Mexico, is a white shark nursery area in the north‐eastern Pacific. Despite existing regulations forbidding the capture of white sharks, incidental catches still occur in some areas. Artisanal fisheries constitute one of the most important economic activities in BSV, yet no formal description of either these fisheries or the incidental catch of juvenile white sharks exists due to the poor data reporting system, thus preventing a clear understanding of the implications of these catches for the white shark population of the north‐eastern Pacific. Artisanal fishing activities and their interactions with juvenile white sharks in BSV are described based on fishermen's knowledge. Artisanal fisheries in BSV are multi‐specific, targeting mostly bottom‐related species (e.g. white seabass and California halibut) that are also common prey for juvenile white sharks. These activities are the only source of income for the majority of fishermen in BSV and are conducted throughout the year, with gillnets being the main fishing gear. White sharks are incidentally caught in bottom gillnets mainly during the summer, although another peak in incidental catch was recorded during winter, possibly related to the presence of juvenile white sharks from California, USA. The most common size of juvenile white sharks incidentally caught was &lt;2 m in the nearshore areas close to the mouth of the Ojo de Liebre Lagoon; larger juveniles (~3 m) were caught in areas near Cedros, Natividad, and San Benito Islands. The multi‐specific nature of BSV artisanal fisheries and their socio‐economic value, and the high post‐release survival of juvenile white sharks suggest that future regulatory actions should focus on the release of incidentally caught live juvenile white sharks and the involvement of the BSV fishing community to increase the effectiveness of management efforts.

Modelling the ingress of a temperate fish larva into a nursery coastal lagoon

The development of sensorial acuity and swimming capabilities of coastal fish larvae and their responses to coastal nursery cues are essential for recruitment success. Most studies of the response of fish larvae to environmental cues and their recruitment into nursery areas have focused on coral reef fish and only a few studies focused on fish species from temperate regions. The Sense Acuity and Behavioural (SAAB) Hypothesis proposes that fish larvae in temperate regions can sense nursery cues and ingress into estuarine ecosystems by using several active swimming strategies. We tested the SAAB hypothesis by studying the ingress of a temperate fish larvae – white seabream Diplodus sargus (Linnaeus, 1758) – into a coastal nursery area, the Ria Formosa Lagoon, Portugal. We combined the results from studies of sensory acuity, swimming capabilities and personality traits of post-flexion larvae with a fine-scale biophysical model to quantify the ingress of the white seabream into the lagoon. Data showed that the location of spawning sites and the directional swimming capabilities are both important for the successful ingress of white seabream larvae into the lagoon. Recruitment was higher when spawning grounds were located in areas with depths between 15.1 and 16.9 m and when post-flexion larvae used their directional swimming capabilities. The larvae ingressed passively into the lagoon with the tidal currents at pre-flexion stage and actively by using their directional swimming capabilities at post-flexion stage. Directional swimming also prevented larval export into the coastal area. When spawning occurred away from the seagrass smell plume emanating from the lagoon, the fish larvae were advected away and lost at sea. This work demonstrated the relevance of combining fish larvae behaviour and oceanography processes in modelling the dispersion of fish larvae to estimate recruitment.

Is summer growth reduction related to feeding guild? A test for a benthic juvenile flatfish sole (Solea solea) in a temperate coastal area, the western Wadden Sea

Flatfish species are an important target for fisheries. During their juvenile stage they concentrate in coastal nursery areas. Food conditions in these areas are an important factor determining habitat quality and ultimate survival. Recently, growth reduction in summer has been observed in plaice, Pleuronectes platessa, feeding on both epibenthic and benthic prey. In the current study, we test the hypothesis that summer growth reduction is a consequence of a reduced availability of benthic prey by analysing summer growth in a fully benthic feeding flatfish, juvenile sole (Solea solea). Summer growth was studied for contrasting years with respect to preceding winter water temperature conditions to exclude possible irreversible non-genetic adaptations of growth to water temperature. Individual growth, estimated from otolith daily rings, was compared with predictions of maximum growth at the prevailing temperature. In line with expectations, 0-group sole showed strong summer growth reduction, supporting the notion that summer growth reduction is related to feeding modes. Summer growth reduction underlines the importance of a good definition of how and over what time period growth as indicator of habitat quality is estimated and compared.

Stomach content and stable isotopes reveal an ontogenetic dietary shift of young-of-the-year scalloped hammerhead sharks (Sphyrna lewini) inhabiting coastal nursery areas

Sphyrna lewini is a placental viviparous shark that uses coastal nursery areas in Jalisco, Mexico, where pups stay 4–12 months. Changes in size or swimming speed may be reflected in diet composition. The main objectives of this study were as follows: (1) analyze the differences in trophic ecology of juvenile S. lewini from coastal nursery areas of Jalisco by sex and size, through stomach content and stable isotope analyses; and (2) analyze changes in muscle and liver δ15N and δ13C values with shark size. Samples were collected from the artisanal fishery from September 2013 to December 2016. Three size classes were compared: neonates, stretched total length (STL) ≤ 75 cm, and STL > 75 cm (75–100 cm). Bony fishes were the most important group in all size classes, and the importance of shrimps decreased with STL. Significant differences in diet composition were found between neonates and STL > 75 cm, which showed the lowest niche overlap (0.32). STL ≤ 75 cm showed the largest niche width (0.75). The δ15N muscle and liver values declined with total length, reflecting the maternal isotopic signal. No differences in liver δ13C values were observed among size classes, but larger size class showed higher muscle δ13C values. Both isotope and stomach content analyses classified all sharks as tertiary consumers, but the trophic position (TP) estimated using δ15N was higher in neonates. No significant differences in the diet and TP were observed between sexes. The liver C:N ratio decreased sharply with STL up to 55 cm, from which increased smoothly, reflecting the lipid reserves consumed during their neonatal stage.

Swimming Abilities of Temperate Pelagic Fish Larvae Prove that They May Control Their Dispersion in Coastal Areas

The Sense Acuity and Behavioral (SAAB) Hypothesis proposes that the swimming capabilities and sensorial acuity of temperate fish larvae allows them to find and swim towards coastal nursery areas, which are crucial for their recruitment. To gather further evidence to support this theory, it is necessary to understand how horizontal swimming capability varies along fish larvae ontogeny. Therefore, we studied the swimming capability of white seabream Diplodus sargus (Linnaeus, 1758) larvae along ontogeny, and their relationship with physiological condition. Thus, critical swimming speed (Ucrit) and the distance swam (km) during endurance tests were determined for fish larvae from 15 to 55 days post-hatching (DPH), and their physiological condition (RNA, DNA and protein contents) was assessed. The critical swimming speed of white seabream larvae increased along ontogeny from 1.1 cm s−1 (15 DPH) to 23 cm s−1 (50 and 55 DPH), and the distance swam by larvae in the endurance experiments increased from 0.01 km (15 DPH) to 86.5 km (45 DPH). This finding supports one of the premises of the SAAB hypothesis, which proposes that fish larvae can influence their transport and distribution in coastal areas due to their swimming capabilities. The relationship between larvae’s physiological condition and swimming capabilities were not evident in this study. Overall, this study provides critical information for understanding the link between population dynamics and connectivity with the management and conservation of fish stocks.

Fine-scale movements of juvenile blacktip reef sharks Carcharhinus melanopterus in a shallow nearshore nursery

Limited information is available on the fine-scale movements and habitat use of juvenile sharks in very shallow (<1 m) nearshore areas and the factors that drive these behaviours. Active acoustic tracking was used to investigate movements and habitat use of juvenile (683 +/- 58 mm total length; mean +/- SD) blacktip reef sharks Carcharhinus melanopterus at Orpheus Island, Australia. Six juveniles were tracked by foot and boat for over 62 h. Juveniles moved in synchrony with tidal cycles, always remaining within very shallow (<1 m) sandy reef flat or reef crest waters during outgoing, low and incoming tides, and using inundated mangrove habitat during higher tides, indicating that tidal fluctuations were a major driver of movement and habitat use. Individuals never left the bay where they were captured or entered deep water beyond the fringing reef, restricting their movements within water <60 cm deep. In general, linearity and rate of movement were significantly higher during incoming or outgoing tides, whereas these measures were significantly lower during higher tide heights when juveniles were occupying mangrove habitats. The observed behaviour was most likely a predator-avoidance strategy, highlighting the importance of mangrove root habitat use by juvenile blacktip reef sharks in coastal nursery areas and indicating that this may be an essential habitat for the young of this species.

Modelling of larval dispersal of Baltic flounder (Platichthys solemdali) revealed drifting depth as a major factor determining opportunities for local retention vs large-scale connectivity

For flatfishes, transportation of larvae to nursery areas is regarded a key mechanism for recruitment, with adaptations in larval behaviour to reach a suitable habitat. Here we model different possibilities of larval drifting of coastal spawning Baltic flounder Platichthys solemdali (recently identified as a species from European flounder P. flesus) to reveal opportunities for local retention vs large-scale dispersal to ensure settling in coastal nursery areas. Drifting depth, duration of drifting and effects of year and time during season were modelled using 1) a high-resolution local dispersal model, and 2) a large-scale connectivity database. The outcome revealed drifting depth as a major factor affecting larval dispersal. Drift at 10–22 m depth involved retention along the coast with the majority of larvae (≥94% or 69–93% according to 1 and 2, respectively) with end points ≤20 km from the coast enabling further successful migration to nursery habitats. Contrary, larval drift close to the surface resulted in advection with end points in the open sea (72–76%), i.e. loss of larvae, but with a small fraction (5–12%) displaying cross-basin connectivity. The results suggest, in agreement with depth distribution of spawning, a larval behaviour promoting drift in the lower part of the water mass, favouring retention close to coastal nursery areas. Obtained dispersal patterns may sustain both local recruitment but also connectivity with other areas, potentially explaining the low genetic diversity between areas for P. solemdali. Low inter-annual variability in dispersal patterns when drifting at 10–22 m depth suggests that larval drift is not a major bottleneck explaining recruitment variability in P. solemdali in the area. The study highlights the differences in life-history strategies of the species pair of flounder in the Baltic Sea; P. flesus spawning in the deep basins with extensive larval dispersal, and coastal spawning P. solemdali with, according to the model outcome, mainly local larval dispersal for sustaining a viable population, i.e. request for different management strategies.

Pilot acoustic tracking study on young of the year scalloped hammerhead sharks, Sphyrna lewini, within a coastal nursery area in Jalisco, Mexico.

A preliminary experience to study, on a small scale, the movements of the young of the year (YOY) Sphyrna lewini (Griffith & Smith, 1834), in the Mexican Central Pacific, using acoustic telemetry within a nursery area. From October to December 2014 seven sharks were tagged with ultrasonic transmitters and tracked for 68 days within a 14 km2 area associated to a river mouth. The quick shark handling allowed their release in less than two minutes and excellent health condition. Although recaptured sharks up to 105 days after tagging did not show symptoms of scar infection, a slight abrasion in the shark skin was observed after 51 days. The ultrasonic transmitter retention was 75%, and the site fidelity was complete (F = 1) during the first ninety days. For the 135-day period, fidelity was 0.63 (0.40-0.80), and the estimated attrition rate was 0.73 (0.34-1). Ninety-seven percent of detections occurred on soft bottoms and less than 30 m depth. The YOY S. lewini stayed active 24 h a day and performed estimated movements of 11.96 km during that time. The home range for all tagged sharks was estimated to be 4.82 km 2 using the minimum convex polygon method (MCP) and 4.89 km 2 using the kernel utilization distribution method (95% KUD). The KUD estimation showed two core areas within the study area, is the one located in front of the river mouth the most used.

Characteristics and sources of anthropogenic and biogenic hydrocarbons in sediments from the coast of Qatar

Surface sediment samples from the coastal zone of Qatar were collected and analyzed to determine the characteristics, and sources of anthropogenic and biogenic hydrocarbons. The main compounds in these surface sediments included n-alkanes, methyl n-alkanoates, diterpenoids, hopanes, steranes, phthalate esters, polycyclic aromatic hydrocarbons (PAHs) and unresolved complex mixture (UCM). Their total concentrations ranged from 18.7±3.7–81.1±7.5ng/g (3.7±0.6–10.4±4.8%) for n-alkanes, 8.3±2.3–51±3.4ng/g (3.0±2.0–5.6±2.0%) for methyl n-alkanoates, 1.8±0.1–10.5±1.0ng/g (1.0±0.5–0.4±0.1%) for diterpenoids, 0.0–79.3±7.4ng/g (0.0–7.9±0.6%) for hopanes, 0.0–32.9±7.9ng/g (0.0–6.5±1.0%) for steranes, 0.7±0.1–36.3±3.4ng/g (0.1±0.1–1.9±3.4%) for phthalates, 0.30±0.2–7.8±0.7ng/g (0.02±0.04–0.42±0.72%) for PAHs, and 38±9–609±57ng/g (38.5±13.4–56.5±13.4%) for UCM. The major sources of these lipids were anthropogenic petroleum residues and plasticizers (80–89%), with lesser amounts from natural higher plants and microbial residues (11–20%). Petroleum residues and plasticizer inputs to the coastal sediments of Qatar likely affect the marine ecosystems and associated species groups as well as shallow coastal nursery and spawning areas.

Variation that can be expected when using particle tracking models in connectivity studies

Hydrodynamic Ocean Circulation Models and Lagrangian particle tracking models are valuable tools e.g. in coastal ecology to identify the connectivity between offshore spawning and coastal nursery areas of commercially important fish, for risk assessment and more for defining or evaluating marine protected areas. Most studies are based on only one model and do not provide levels of uncertainty. Here this uncertainty was addressed by applying a suite of 11 North Sea models to test what variability can be expected concerning connectivity. Different notional test cases were calculated related to three important and well-studied North Sea fish species: herring (Clupea harengus), and the flatfishes sole (Solea solea) and plaice (Pleuronectes platessa). For sole and plaice we determined which fraction of particles released in the respective spawning areas would reach a coastal marine protected area. For herring we determined the fraction located in a wind park after a predefined time span. As temperature is more and more a focus especially in biological and global change studies, furthermore inter-model variability in temperatures experienced by the virtual particles was determined. The main focus was on the transport variability originating from the physical models and thus biological behavior was not included. Depending on the scenario, median experienced temperatures differed by 3°C between years. The range between the different models in one year was comparable to this temperature range observed between modelled years. Connectivity between flatfish spawning areas and the coastal protected area was highly dependent on the release location and spawning time. No particles released in the English Channel in the sole scenario reached the protected area while up to 20% of the particles released in the plaice scenario did. Interannual trends in transport directions and connectivity rates were comparable between models but absolute values displayed high variations. Most models showed systematic biases during all years in comparison to the ensemble median, indicating that in general interannual variation was represented but absolute values varied. In conclusion: variability between models is generally high and management decisions or scientific analysis using absolute values from only one single model might be biased and results or conclusions drawn from such studies need to be treated with caution. We further concluded that more true validation data for particle modelling are required.