The spatial and temporal variability in the relative abundance of the post-larvae (PL) and juvenile (JU) stages of the pink shrimp Farfantepenaeus paulensis was investigated in the estuary of Lagoa dos Patos, southern Brazil. This analysis enabled the identification of differential distribution patterns. Pink shrimp abundance was studied to understand what factors influence the occupation of the estuary. Monthly samples were taken with a trawl net at 12 sites in the estuary from September 2010 to January 2013. Comparisons were made between protected and unprotected sites. Both PL and JU had a wide distribution in the estuary. The temperature was not a significant variable for explaining abundance variability. The abundance of PL increased with salinity and influenced PL entry to the estuary. The highest abundances of PL were found in unprotected areas and protected sites at the mouth of the estuary, while juveniles were unevenly distributed with higher abundance in protected areas. Recruitment period of PL in the estuary was October to March, and of juveniles was November to February. We suggest that the preservation of unprotected shallow waters and protected areas at the mouth of the estuary are key to further recruitment of the species in the estuary.

Nephrops norvegicus is a commercially valuable demersal fisheries species. Relatively little is understood about this species’ population dynamics across its distribution with previous mitochondrial and microsatellite studies failing to identify significant population-level differentiation. In this study, sequence variation in the mitochondrial (mtDNA) D-loop was analysed from samples across the distribution range, and compared with COI sequences for this species retrieved from GenBank. Analysis of a 375 bp fragment of the D-loop revealed significant genetic differentiation between samples from the North-east Atlantic and the east Mediterranean (FST = 0.107, P < 0.001). Tau (τ), theta (θ0 and θ1) and Fu's FS values suggest the species spread between 10,500 to 19,000 ybp and subsequently expanded rapidly across the Atlantic.

Although common in the Mediterranean, the morphological and biological characteristics of the moray eel Muraena helena are largely unknown. This study, based on 310 specimens caught using a longline at a depth of 50–100 m, addresses this knowledge gap for northern Tunisia, which is a stronghold of the species. There were significantly more males than females, with a sex ratio of 1:1.5. The number of vertebrae between individuals were variable, especially abdominal and caudal vertebrae (range 56–72; 70–84, respectively). Overall, the total number of vertebrae was less variable (138–146 ± 3.6 SE) and similar between males and females. The length-length relationship recorded for M. helena is provided for the first time, with the pre-anal length (paL), pre-dorsal length (pdL) and the head length (hL) growing faster than the total length (TL). According to the weight-length relationship (WLR), positive allometric growth was established for males (b = 3.6), females (b = 3.46) and combined sexes (b = 3.54). The relative condition factor (CF) did not show significant differences between seasons. The gonadosomatic index (GSI) indicated a significant difference between the seasons for females, whilst the hepatosomatic index (HSI) highlighted a significant difference between seasons for both males and females.

Phenotypic differentiation among fish populations may be used for management of distinct stocks and helps in conserving biodiversity. We compared morphometric and meristic characters of the anchovy Anchoa januaria from shallow semi-closed bays between the south-eastern (Tropical, 23°S) and southern (Subtropical, 25°S) Brazilian coast. We hypothesized that differences between habitats and environmental conditions result in morphological divergence between conspecific populations. Fish size did not differ significantly between the two areas. Significant differences in the meristic and morphological characters were detected for individuals between the two areas, with specimens from the Subtropical region having significant larger head height, pectoral fin length and eye diameter compared with those from the Tropical region. Conversely, specimens from the Tropical region had significantly larger maxillary length, mouth length and body height than those from the Subtropical region. The number of rays for the dorsal and pectoral fins were higher for the specimens from the Subtropical region, whereas for the anal fin was higher for individuals from the Tropical region. Different morphological groups between the two regions were depicted by principal component analysis and discriminant function analysis, which suggest that morphological divergence is occurring. Local environmental influences and the lack of genetic interchange are likely to be the causes of such divergence. This is facilitated by the low tolerance of this species to marine waters that prevents connectivity between these stocks/populations.

Reproductive biology of Atlantic chub mackerel (Scomber colias) was studied based on samples from commercial catches in M'diq Bay, Morocco. Females predominated in the total catch (54%), their size at first maturity being 19.19 ± 0.43 cm TL. A minimum landing size (MLS) of 21 cm is suggested. The oocyte size frequency distribution and histological analysis confirmed that S. colias is a species with an indeterminate fecundity. The batch fecundity was estimated as 18,452–131,642, with a mean of 60,022 oocytes. The relative batch fecundity was 157–360, with a mean of 279 eggs g−1.

Age and growth parameters were estimated for the deep-sea cardinalfish (Epigonus crassicaudus) from sagittal otoliths collected between 2012 and 2015 onboard commercial fishing vessels from the South-east Pacific off Chile between 33°04′S and 41°46′S. Von Bertalanffy growth parameters (VBGP) were estimated from assumed annual otolith growth zone counts. The verification of the first annulus of sagittal otoliths was determined by examining in detail daily micro-increments. These data helped inform the interpretation of the annual growth zones from transverse otolith sections. The von Bertalanffy growth model estimated to length-at-age data were asymptotic length (L∞) of 34.1 cm fork length (FL), a growth coefficient (k) of 0.1 cm/year and a t-zero (t0) of −0.85. The maximum ages observed were 67 and 65 years for female and male fish, respectively.

The early life history traits of the labrisomid blenny Auchenionchus crinitus (Jenyns, 1842) from subtidal rocky reefs were studied, based on microstructure analysis of sagittae of their pelagic larvae (4.01 mm NL −12.50 mm SL). Ichthyoplankton was collected in shallow (<20 m) nearshore waters off Isla Santa María, Antofagasta, northern Chile every 15 days during austral autumn–winter 2014 (five sampling days). During late May and early June, larval abundance was low (median ± MAD, 39.06 ± 5.08 ind. 100 m−3), increasing significantly during mid-June to early August (110.98 ± 47.66 ind. 100 m−3). Using 354 sagittae, the back-calculated hatch dates indicated the occurrence of three hatching events, two in autumn and one in winter. Hatching occurred mainly during the illuminated phases of the lunar cycle. All three batches had similar estimated larval sizes at hatch (3.2–3.7 mm SL), as well as similar growth rates (0.19–0.22 mm day−1) during the first 30 days of life. During the study period, shallow waters were well mixed, with seawater temperature of 14.73 ± 0.58°C and salinity of 34.84 ± 0.04. This is the first estimation of early life history traits of this cryptobenthic species from rocky reefs of Chile.

Solea aegyptiaca (Chabanaud, 1927) is one of the most common Soleid species in southern Tunisian waters. This study provides the first detailed information on the reproduction biology of S. aegyptiaca in these areas. Samples of S. aegyptiaca were collected by trawl from the Gulf of Gabes (Tunisia) between April 2013 and March 2015. A total of 1638 specimens were examined, ranging from 9.7 to 30.7 cm total length. The sex ratio was in favour of males in smaller size classes and females in larger size classes. The macroscopic analysis of the gonads and the progression of the monthly values of the gonadosomatic index (GSI) indicated that the reproductive season extended from October to February, with GSI peaking in November and December for males and females respectively, and that spawning occurs once a year from November to February. The utilization of lipid reserves, stored predominantly in the liver as well as in muscles, was depicted. The estimated average length at first maturity was 22.31 ± 0.41 cm for males and 23.19 ± 0.184 cm for females. Total fecundity of mature females ranged from 14,160–62,700 eggs per fish, showing a significant increase with size, with an average of 33,020 ± 5239 eggs per fish.

Fatty acids (FA) analysis is a well-established approach for qualitatively studying feeding preferences. In the Argentinean Continental Shelf, Argentine hake Merluccius hubbsi supports the major demersal finfish fishery. The Patagonian stock of the species spawns and nurses in austral summer in the north Patagonian shelf (NPS, 43°–45°30′S). Previous studies about larval feeding in the NPS have solely focused on gut contents, indicating selectivity upon calanoid copepods. Hence, our main objective was to apply the FA approach to confirm and/or broaden M. hubbsi larval food selection. Hake larvae and copepod FA profiles overlapped significantly, dominated by the saturated FA 16:0, the monounsaturated FAs 18:1n-9 and 22:1n-9, and the polyunsaturated FA 22:6n-3. Moreover, identified markers typical of bacteria (15:0, 17:0) and dinoflagellates (18:4n-3, 22:6n-3) suggest a microbial input at the base of the NPS food web, with the latter probably acting as an intermediate step between bacteria and hake larvae. Possible direct predation upon protozoans by larvae is postulated, broadening the known trophic spectrum derived from classical diet analyses. The FA approach allowed us to clarify feeding preferences in the NPS, with data being relevant in the context of hake recruitment studies.

The objective of the study was to investigate the seasonal variations in proximate and fatty acid composition of wild sobaity (Sparidentex hasta) for a one-year period during (i) pre-spawning (October–December), (ii) spawning (January–March), (iii) post-spawning (April–June) and summer (July–September). Five male and five female fish were collected from market each month and used for the study. Skinless fillets from both sides of sobaity were taken, chopped, minced, frozen and freeze dried. Freeze-dried ground male and female fish samples were pooled separately and homogenized for proximate composition and fatty acid analysis. The results of the investigation showed that the muscle proximate composition and fatty acid profile of sobaity differed significantly (P < 0.05) among different seasons with the highest muscle lipid during the pre-spawning and spawning season. Palmitic acid (C16:0) was the most dominant muscle fatty acid followed by oleic acid (C18:1n-9). The muscle docosahexaenoic acid (DHA, C22:6n-3) levels in pre-spawning and spawning seasons were significantly (P < 0.05) higher than those in other seasons. A good n-3/n-6 ratio (2.26–3.11) and the higher DHA levels (10.16–11.47%) observed in muscles during the pre-spawning and spawning season indicated a better nutritional value of sobaity at this time of the year.

Periodic fish ingressions into intertidal areas during high tide are known to occur on tropical mudflats. This study aimed to elucidate the feeding ground function of coastal mudflats for three common stingray species in the Klang Strait, Malaysia. Stingrays (disc width range from 5.65–54.50 cm) sampled over 17 months using a large barrier net (~2 ha enclosure) at two sampling sites were examined for their diet composition, prey frequency and prey volume according to predator species and maturity. The index of relative importance and Schoener's index of diet overlap were calculated. The three stingray species fed on relatively similar prey items which varied in size and contribution. Brevitrygon heterura fed on the widest range of prey taxa (28) whereas Hemitrygon bennetti (22) and Telatrygon biasa (17) showed higher prey specialization. The Penaeidae (dominantly Metapenaeus brevicornis and M. affinis) were the most important food item in the stingray diet which also included Actinopterygii, Amphipoda, Brachyura and Calanoida. The stingray diet showed an ontogenetic shift, with young stingrays tending to be generalists whereas the more mature stingrays (except H. bennetti) become more specialized in their feeding habits. This shift in feeding strategy reflects the diversity of prey taxa abundantly available to young stingrays on the mudflats, while the larger stingrays adapt to feed on larger prey once they enter deeper waters.

The Istanbul Strait is an important cetacean habitat that is intensely used by humans. Yet little is known about their spatial-temporal distribution. To understand the encounter rates and residency patterns of bottlenose dolphins, photo-identification data were collected between 2011 and 2016 in the Istanbul Strait. The study showed that bottlenose dolphins are a regular, year-round component of the strait. The encounter rate was estimated to be four groups (22 individuals) per 10 km. The adjacent waters of Marmara Sea and Black Sea, that host relatively less marine traffic, had the highest number of encounters in the area. Conversely, the middle sections had the lowest number of encounters but the highest marine vessel density. Further, the encounter rates dropped to zero in the fishing zones, where the number of purse seines reached up to 100 per day. Additionally, dolphins showed varying degrees of residency patterns, with multi-year re-sightings. Maximum re-sighting distance was up to 35 km, which is more than the total length of the strait. This movement pattern should be investigated as it might reveal possible migration between local populations. This study finds that the Istanbul Strait serves as a critical habitat for the regional bottlenose dolphin populations and they are likely to be a part of a resident local population with a home range extending the length of the strait. Dedicated surveys with inter-regional collaborations are needed to evaluate the home range and population status of this endangered species for their effective conservation in one of the busiest waterways of the world.

Perhaps the world's best-known cetacean, the bottlenose dolphin shows considerable variation in behaviour between and within populations in relation to differences in natural and anthropogenic conditions. Drivers of behavioural variation need to be identified to understand the dynamics of wild dolphin populations. Little research has been published on the bottlenose dolphin population found in the Southern Adriatic Sea. Using a set of spatial, temporal and social predictors, we aimed to investigate what variables are related to the behaviour of an under-studied population of bottlenose dolphins along the coastline of Montenegro. We present the results of a year-long study monitoring the behaviour of bottlenose dolphins along coastal Montenegro. We considered the effect of topography, seasonality and group size. A large proportion of travelling (55%) small groups (mean 4, range 1–9) in shallow waters (<50 m) was observed. We showed that seasonality alone explained behaviour best, with surface-feeding and socializing-resting increasing in autumn and winter. Group size was found to be a result of behavioural choice. We suggest seasonal changes in environmental conditions and anthropogenic pressure may explain the recorded behavioural pattern. This research points to the necessity of increased collaboration in the region to help understand complex patterns in behaviour and habitat use of local dolphin populations if effective conservation measures are to be developed.