Exploring connectivity between spawning and nursery areas of Mullus barbatus (L., 1758) in the Mediterranean through a dispersal model

Connectivity between spawning and nursery areas plays a major role in determining the spatial structure of fish populations and the boundaries of stock units. Here, the potential effects of surface current on a red mullet population in the Central Mediterranean were simulated using a physical oceanographic model. Red mullet larvae were represented as Lagrangian drifters released in known spawning areas of the Strait of Sicily (SoS), which represents one of the most productive demersal fishing‐grounds of the Mediterranean. To consider the effect of inter‐annual variability of oceanographic patterns, numerical simulations were performed for the spawning seasons from 1999 to 2012. The main goal was to explore connectivity between population subunits, in terms of spawning and nursery areas, inhabiting the northern (Sicilian‐Maltese) and southern (African) continental shelves of the SoS. The numerical simulations revealed a certain degree of connectivity between the Sicilian–Maltese and the African sides of the SoS. Connectivity is present in both directions, but it is stronger from the Sicilian–Maltese spawning areas to the African nurseries owing to the marine circulation features of the region. However, because the majority of the larvae are transported to areas unsuitable for settlement or outside the SoS, the dispersal process is characterized by a strong loss of potential settlers born in the spawning areas. These results are in agreement with the low genetic heterogeneity reported for this species in the Mediterranean Sea and support the existence of a metapopulation structure of red mullet in the SoS and the adjacent areas.     

The pelagic habitat analysis module for ecosystem‐based fisheries science and management

We have developed a set of tools that operate within an aquatic geographic information system to improve the accessibility, and usability of remote‐sensed satellite and computer‐modeled oceanographic data for marine science and ecosystem‐based management. The tools form the Pelagic Habitat Analysis Module (PHAM), which can be applied as a modeling platform, an investigative aid in scientific research, or utilized as a decision support system for marine ecological management. Applications include fisheries, marine biology, physical and biological oceanography, and marine spatial management. The GIS provides a home for diverse data types and automated tools for downloading remote sensed and global circulation model data. Within the GIS environment, PHAM provides a framework for seamless interactive four‐dimensional visualization, for matching between disparate data types, for flexible statistic or mechanistic model development, and for dynamic application of user developed models for habitat, density, and probability predictions. Here we describe PHAM in the context of ecosystem‐based fisheries management, and present results from case study projects which guided development. In the first, an analysis of the purse seine fishery for tropical tuna in the eastern Pacific Ocean revealed oceanographic drivers of the catch distribution and the influence of climate‐driven circulation patterns on the location of fishing grounds. To support management of the Common Thresher Shark (Alopias vulpinus) in the California Current Ecosystem, a simple empirical habitat utilization model was developed and used to dynamically predict the seasonal range expansion of common thresher shark based on oceanographic conditions.     

Influence of mapping resolution on assessments of stream and streamside conditions: lessons from coastal Oregon,USA

• 1. Digital hydrographic data are commonly employed in research, planning, and monitoring for freshwater conservation, but hydrographic datasets differ in spatial resolution and accuracy of spatial representation, possibly leading to inaccurate conclusions or unsuitable policies for streams and streamside areas.
• 2. To examine and illustrate the potential for different hydrographic datasets to influence in‐channel and streamside characterizations, a study area in the US Pacific Northwest was chosen because 1:100 000, 1:24 000, and densified 1:24 000 hydrography are available and widely used in research and management for several species of Pacific salmon and trout at risk. The potential was examined for differences among the digital hydrographic datasets in: (1) spatial extent to influence estimated abundances of fish habitat, streamside buffer conditions, and fish distributions; and (2) spatial position to influence estimated streamside buffer conditions and estimated stream gradient.
• 3. The analysis of spatial extent found the total stream length represented by the 1:100 000 hydrography was approximately one half that of 1:24 000 hydrography and only one fifth that of densified 1:24 000 hydrography. The 1:100 000 and 1:24 000 networks differed significantly for 13 out of 18 fish habitat attributes, and the three hydrographic datasets differed significantly for many characteristics in streamside buffers; fish distributions mapped at 1:24 000 added 6–14% of stream length to 1:100 000 distributions. The analysis of spatial position found few differences between the 1:100 000 and 1:24 000 hydrography in streamside buffer characteristics but significant differences in channel gradient.
• 4. Overall, hydrographic datasets differed only slightly in spatial position but differed in spatial extent to the point of representing different populations of streams. If species inhabiting larger streams (greater mean annual discharge) are of interest, then results derived from studies based on 1:100 000 hydrography should prove useful. However, higher‐resolution hydrography can be critical when designing and implementing strategies to protect fish and other aquatic species at risk in smaller streams.

Copyright © 2008 John Wiley & Sons, Ltd.     

The relationship between the skipjack tuna (Katsuwonus pelamis) fishery and seasonal temperature variability in the south-western Atlantic

The spatio‐temporal distribution of tuna fishing effort has been related to oceanographic circulation and features in several seas of the world. Understanding the relationship between environmental variables and fishery resource dynamics is important for management decisions and to improve fishery yields. The relationship between sea temperature variability and the pole‐and‐line skipjack tuna (Katsuwonus pelamis) fishery in the south‐western Atlantic Ocean was investigated in this work. Data from logbooks, satellite images (sea surface temperature), and oceanographic surveys were used in the analyses. Skipjack are caught in warm tropical waters of the Brazil Current (BC). The north–south displacement of fishing effort was strongly associated to seasonal variation of the surface temperature, which was coupled to the tropical BC flow. Oceanographic fronts from autumn to spring and a shallow thermocline in summer probably induces the aggregation of skipjack schools over the shelfbreak, favouring fishing operations. Hypotheses are proposed to explain the relationship between peaks of fishing events and the presence of topographic peculiarities of the shelfbreak.     

Migration model of post‐smolt Atlantic salmon (Salmo salar) in the Gulf of Maine

Understanding how oceanographic factors independently and interactively influence fish behavior, physiology, and survival is essential for predicting the impact of climate change on fish. Such predictions are especially challenging for highly migratory species such as salmon that experience a broad range of conditions. We applied a novel modeling approach that combines an individual‐based particle model with a bioenergetics model to evaluate the effects of oceanographic variability on migration of post‐smolt Atlantic salmon (Salmo salar). Interannual variability in the surface current velocity and sea surface temperature differentially influenced post‐smolt salmon migration. The magnitude, duration, and direction of the currents relative to a fish's intended swimming direction had the strongest influence on migration. Changes in ocean circulation led to changes in currents at a regional scale that have a similar, relative effect across multiple populations during out‐migration. Results of this study suggest that the Nova Scotia Coastal Current has a strong influence on the migration pathways of migrating salmon through the Gulf of Maine. The influx of cool fresh water from the Arctic, observed in the early 1990s, changed the Nova Scotia Coastal Current and, as suggested by model results, could have dramatically influenced post‐smolt salmon migration success. There was a trade‐off between arriving at the destination quickly but at a small size and not arriving at the destination at all. Fish that took a long time to migrate had more opportunities to feed and encountered warmer summer waters, increasing their overall growth.     

From monsoons to mantas: seasonal distribution of Manta alfredi in the Maldives

The Republic of Maldives in the central Indian Ocean is home to large numbers of manta rays, Manta alfredi. They are known to undertake seasonal migrations within the Maldives, but these movements have not been well documented. The aims of this study were to map the seasonal distribution of manta rays within the Maldives, and to provide some indications of the physical and biological oceanographic processes affecting their distribution. The seasonal distribution of mantas was determined from a national survey of fishermen, interviews with experienced divers and personal observations. The data demonstrate that the distribution of mantas is strongly influenced by the seasonally reversing monsoon currents. Mantas occur on the downstream sides of the atolls, and are rare on the upstream sides, switching sides biannually as the monsoon currents change direction. These seasonally alternating currents are driven by monsoon winds which also alternate according to the season, and bring clear oceanic water to the upstream sides of the atolls. As the currents pass over the Maldives ridge, nutrient‐rich waters are lifted to the surface, promoting phytoplankton blooms (as demonstrated by the distribution of chlorophyll‐a) on the downstream sides of the atolls. This manifestation of the island mass effect supports an abundance of zooplankton, which in turn supports the manta rays.     

Habitat differentiation between sei (Balaenoptera borealis) and Bryde's whales (B. brydei) in the western North Pacific

Two closely related baleen whale species, sei and Bryde's whales, in the western North Pacific were studied to identify differences in habitat use. Data were obtained from May to August 2004 and 2005. This study examined the relationship between oceanographic features derived from satellite data and the distribution of sei and Bryde's whales using basic statistics. We investigated oceanographic features including sea surface temperature (SST), sea surface chlorophyll a (Chl‐a), sea surface height anomalies (SSHAs), and depth of the habitat. These two whale species used habitats with different SST, Chl‐a, and SSHA ranges. The 0.25 mg m^?3 Chl‐a contour (similar to the definition of the Transition Zone Chlorophyll Front) was a good indicator that separated the habitats of sei and Bryde's whales. Then generalized linear models were used to model the probabilities that the whale species would be present in a habitat and to estimate their habitat distribution throughout the study area as a function of environmental variables. The potential habitats of the two species were clearly divided, and the boundary moved north with seasonal progression. The habitat partitioning results indicated that SST contributed to the patterns of habitat‐use and might reflect differences in prey species between the two whales. This study showed that the habitats of the sei and Bryde's whales were clearly divided and their potential habitat‐use changed seasonally.     

Interannual and spatial variation in the population genetic composition of young‐of‐the‐year Pacific ocean perch (Sebastes alutus) in the Gulf of Alaska

Little is known about the population structure of Alaskan rockfishes, including Pacific ocean perch (POP, Sebastes alutus), and how persistent and variable oceanographic features may influence their structures. Moreover, early life history information is sparse for many species. We used data from 14 microsatellite loci to characterize the genetic structure of young‐of‐the‐year Pacific ocean perch collected during 1998–2003 from the Gulf of Alaska and Bering Sea. Broad‐scale geographic variation in genetic structure of the young‐of‐the‐year (F_ST = 0.005, P < 10^?4) had similarities to that observed in a previous adult study. The overall correlation between genetic and geographic distance (isolation by distance) was nearly identical to that observed in the adults. Fine‐scale geographic divergence was also observed and may be the result of oceanographic circulation features within the Gulf of Alaska. Interannual variation (between cohorts) at locations sampled in more than one year is consistent with variable oceanography and fine‐scale population structure rather than the influence of a sweepstakes effect. The similarities of the young‐of‐the‐year with the adults and the pattern of genetic divergence confirm that dispersal of Pacific ocean perch is limited in all life stages.     

Seasonal changes in otolith increment width trajectories and the effect of temperature on the daily growth rate of young sardines

We studied the otolith microstructure and growth of sardine, Sardina pilchardus, in the North Aegean Sea (eastern Mediterranean Sea), using samples of larvae and juveniles that had hatched in winter (November–January) and winter–spring (February–May), respectively. The juveniles had developed during an extended period coinciding with marked pelagic ecosystem changes (from winter, mixed conditions to summer, stratified waters). To examine the relationship between environmental changes and the observed variability in their otolith increment–width trajectories (width‐at‐age), we summarized the shape of trajectories with a four‐parameter set estimated from a growth model fit to each width trajectory. The individual parameter sets were then related to the potential oceanographic conditions that fish experienced during their development, derived from a hydrodynamic–biogeochemical model (POM‐ERSEM), implemented in the sampling area. Substantial seasonal effects were demonstrated on the otolith microstructure (platykurtic versus leptokurtic trajectories in winter‐mixed versus summer‐stratified conditions), which were related to the progressive sea surface warming. In a subsequent step, in order to study the effect of oceanographic conditions on larval and juvenile daily growth rates, a GAM (Generalized Additive Model) analysis of otolith increment widths was carried out, using model‐derived oceanographic parameters and taking into account the ‘inherent otolith growth’, expressed by the explanatory variables ‘previous increment width’ and ‘Age’. Results showed a strong and positive, linear effect of temperature on the growth rate of winter‐caught larvae, whereas in juveniles, which had developed within a wide range of temperatures, an optimum temperature for growth was observed at around 24°C.     

Hydrography and spatial variability in the size distribution of phytoplankton along the Kurile Islands in the western subarctic Pacific Ocean

Spatial variability in the size distribution of the phytoplankton community along the Kurile Islands, in the western subarctic Pacific Ocean, was investigated in terms of chlorophyll a concentrations in August and September, 1990. Analysis of dynamic height relative to 1,500 db and temperature–salinity diagrams at 50 m depth revealed five major oceanographic regions in this study area. The characteristic hydrography was clearly related to the surface distribution of chlorophyll a concentrations. As a warm core ring originating from the Kuroshio water was cooled by the surrounding water and meteorological conditions, its physical, chemical, and biological characteristics changed. Dominant picoplankton were replaced by a 10-2 μm size fraction in the warm core ring. In the Oyashio region, physical structures were less variable but concentrations of chlorophyll a were most variable and cells larger than 10 μn dominated. An anticlockwise eddy found in the Oyashio water showed the highest concentration of chlorophyll a. In the Okhotsk region, the chlorophyll standing stock was small with a low percentage of cells larger than 10 μm in spite of high nitrate concentrations. Along the Kurile Islands and Hokkaido Island, the surface mixed layer was not well defined; surface nitrate concentrations were relatively high, and the chlorophyll standing crop was also high with low percentages of picoplankton. The spatial heterogeneity in the dominance of cells larger than 10 μm in phytoplankton assemblages seems to be clearly associated with the effect of nitrate availability determined by water structure.     

Bottom boundary layer cooling and wind‐driven upwelling enhance the catchability of spanner crab (Ranina ranina) in South‐East Queensland,Australia

Species catchability is an important parameter used to help optimise stock assessment modelling and the economic efficiency of commercial fishing operations. Previous studies have shown several physical oceanographic parameters, including ambient temperature, waves and currents, affect the catchability of spanner crabs (Ranina ranina) throughout the Indo‐Pacific. Most notably in the Australian fishery, where oceanographic processes vary over space and time, a positive relationship between bottom boundary layer temperature (BBLT) and catch rates was observed. Here, we aimed to better understand how localised oceanographic processes affected this relationship in the southernmost South‐East Queensland (SEQ) sector of the Australian fishery at seasonal and short temporal scales. Our results show cooler BBLT, upwelling‐favourable alongshore wind stress and increased catch rates occurred during mating season in austral spring. At the end of austral summer, BBLT began warming, downwelling‐favourable winds were dominant, and catch rates declined around the post‐moult period. Outputs from the generalised linear models (GLMs) that separated these effects in each season show that, at shorter temporal scales, daily catch rates also increased with episodic BBLT cooling and upwelling‐favourable alongshore wind stress, but only during austral autumn and winter. These new findings suggest that region‐specific, short‐term and seasonal variability of oceanographic processes responsible for changes in BBLT play an important role in influencing the catchability of spanner crabs. We suggest that the effects of region‐specific physical oceanographic processes must be considered in future work when investigating the catchability of commercially important fisheries species fished over large spatial domains.     

Environmental effects on the spatio‐temporal patterns of abundance and distribution of Sardina pilchardus and sardinella off the Mauritanian coast (North‐West Africa)

From 1998 to 2011, the effects of environmental conditions on the spatial and temporal trends of sardine and sardinella catch rates in the Mauritanian waters were investigated using generalized additive models. Two models were used: a global model and an oceanographic model. The global models explained more of the variability in catch rates (60.4% for sardine and 40% for sardinella) than the oceanographic models (42% for sardine and 32.4% for sardinella). Both species showed clear and inverse seasonal variations in abundances corresponding to their main spawning activities and the hydrologic seasons off the Mauritanian waters. Sardine prefer colder waters and seem to occupy the ‘gap’ in the northern part of the Mauritanian waters as soon as sardinella has left the area because of to lower water temperatures. Unlike sardinella, sardine showed a gradual southward extension between 2002 and 2009. The oceanographic model revealed that a high proportion of catch variability for the two species could be explained by environmental variables. The main environmental parameters explaining the variability are sea surface temperature (SST) and the upwelling index for sardinella, and the chlorophyll‐a (Chl‐a) concentration, the upwelling index and SST for sardine. The sardinella spatio‐temporal variations off Mauritania seem to be more controlled by thermal than productivity gradients, probably linked to the species physiological constraints (thermal tolerance) whereas sardine seems to be more controlled by an ‘optimal upwelling and temperature’ windows. The results presented herein may be useful for understanding the movement of these species along the Mauritanian coast and hence their management under a changing climate.     

A perspective on the importance of oceanic fronts in promoting aggregation of visitors to seamounts

Recent evidence has demonstrated that not all seamounts are areas where productivity, biomass and biodiversity of marine life thrive. Therefore, understanding the drivers and mechanisms underlying seamount productivity is a major challenge in today's seamount research. Incorporating oceanographic data in future analyses has been suggested to be of paramount importance to unveil many of the seamount ecology paradigms. Persistent hydrographic features, such as oceanic fronts, have been recognized to enhance biological activity and to drive marine animal distributions and migration patterns. However, the importance of oceanic fronts in driving aggregations of visiting animals on seamounts has not been understood yet. Here, we analysed a data set of seamounts in the Pacific Ocean alongside satellite‐derived maps of strong, persistent and frequently occurring oceanographic features, to evaluate if oceanic fronts promote aggregation of visitors on seamounts. Our analyses suggest that seamounts with a higher front frequency were more likely to aggregate tuna catch than average seamounts. However, it appears that fronts may be driving factors for aggregation only if present above a certain threshold. These results highlight the importance of environmental conditions in general, and oceanic fronts in particular, in promoting seamount productivity. We therefore argue that a thorough examination of the oceanographic conditions promoting seamount productivity at various temporal and spatial scales is warranted in future seamount research agendas.     

Multiple cohorts of juvenile jack mackerel Trachurus japonicus in waters along the Tsushima Warm Current

The jack mackerel, Trachurus japonicus, has a prolonged spawning season and widely spread spawning grounds. The population in the coastal waters of Japan seems to be composed of several cohorts spawned seasonally from different waters. To understand its population structure along the Tsushima Warm Current, we analysed hatchdates and growth histories of fish from Kunda Bay, the southern, central and northern East China Sea (ECS), the southern Sea of Japan, and Maizuru Bay. Seven cohorts were detected from fish collected between June 2005 and June 2006 in Kunda Bay. Comparing hatchdate distributions and growth trajectories of the seven cohorts with those of the other five regional samples, we did not find that cohorts collected in Kunda Bay originated in the southern ECS. Therefore, these coastal waters of Japan appear to be significant spawning grounds for juvenile jack mackerel.     

Comparing the roles of Pacific halibut and arrowtooth flounder within the Gulf of Alaska ecosystem and fishing economy

The fishing industry of the western and central regions of the coastal Gulf of Alaska (CGoA) directly employs over 17,000 people and processes fish with a wholesale value of US$618 million annually. Pacific halibut (Hippoglossus stenolepis) are a valued groundfish species because of the high quality of their flesh. In contrast, arrowtooth flounder (Atheresthes stomias) are much more abundant but of low value because their flesh degrades upon heating. Both are high trophic level predators but play different roles in the ecosystem because of differences in abundance and diet. Using an end‐to‐end ecosystem model, we evaluate the impact of alternate levels of fishing effort and large‐scale changes in oceanographic conditions upon both species, the ecosystem, and the fishing economy. Reduction of longline efforts to reduce Pacific halibut mortality led to reduction in total value of all CGoA landings but increase in value landed by sport fisheries, trawl fleets, and fish pot vessels as they exploit a greater share of available halibut, sablefish, and Pacific cod. Increased trawl effort to raise arrowtooth flounder mortality led to increase in total value of all landings but large reductions in value landed by longline, jig, fish pot, and sport fleets with greater competition for available Pacific cod, halibut, and sablefish. Oceanographic conditions that enhance pelagic food chains at the expense of benthic food chains negatively impact groundfish in general, though Pacific halibut and arrowtooth flounder are resilient to these effects because of the high importance of pelagic fish in their diets.     

Hydropower operations in groundwater‐influenced rivers: implications for Atlantic salmon,Salmo salar,early life stage development and survival

During their early life stages (egg maturation, hatching, alevin development), between late autumn and early spring, young Atlantic salmon are exposed to surface‐groundwater interactions in the hyporheic zone and may depend on influx of subsurface water during periods of regulated low discharge for survival. Two studies, one in a seasonally regulated river and one in a river exposed to hydropeaking, displayed unexpectedly high survival of eggs in surface de‐watered areas because of the influx of oxygen‐rich subsurface water. Field observations of newly hatched alevins in these two rivers showed them to be more sensitive (i.e. suffered higher mortality from) to surface de‐watering than were eggs. Exposure to dry conditions in drawdown areas was highlighted as the main cause for alevin mortality. Therefore, shorter periods of surface de‐watering in the river with hydropeaking resulted in higher alevin survival than the seasonally regulated river when still permanently drained after egg hatching. Greater consideration should be given to all early life‐history stages when implementing discharge release strategies, and the extent of groundwater influence and the potential for flexible hydropower operations should be taken into account.     

One-dimensional biophysical modelling of fish egg vertical distributions in shelf seas

Modelling the vertical distribution of fish eggs is important when assessing fish stocks with egg production methods and for monitoring the reproductive potential of fish populations. Fish eggs are passive particles and their vertical distribution is determined by a few parameters such as egg density, egg diameter, wind‐ and tide‐induced turbulence, and vertical hydrographic structure. A one‐dimensional vertical biophysical, numerical model was developed which was adapted to the hydrography of shelf seas under the influence of tidal currents, wind‐induced circulation, and river discharges. The biological part of the model parameterized the ascent velocity of the egg as a function of egg properties (diameter, density) and water properties (density, viscosity, turbulence). The model contains a turbulence closure which makes the model dynamic. The model parameters were surface wind, tidal currents, T‐S profile, and egg diameter and density, which were kept constant in time. The model has the capacity to generate sub‐surface egg maxima in different hydrographic conditions, e.g. in areas under the influence of river plumes, and can also homogenize the egg distribution under wind and tide forcing. Sensitivity tests were carried out to study the response of the model to variations in the model parameters for a variety of hydrographic conditions. The modelled egg vertical distributions were validated by comparison of the model results with egg distributions sampled in the field. The analysis highlighted variability in fish egg density of anchovy, sardine, and sprat across years and areas, with a potential link between egg density and surface sea water density. The validated model is a tool for the analysis of shelf seas fish egg vertical distributions.     

Spatial association between northern fur seal (Callorhinus ursinus) and potential prey distribution during the wintering period in the northern Sea of Japan

Elucidating the response of marine predators to oceanographic features helps in understanding their foraging strategies and the cause of their spatial overlap and interference with fishery activities. Northern fur seal is a highly pelagic species during the wintering period. In recent years, fur seals have consistently been found distributed near the coast of southwest Hokkaido, Japan. Because interference by fur seals with coastal fishery activities has become a serious concern, an understanding is sought as to why fur seals come ashore in this area. We conducted ship‐based observations and estimated fur seal density. To elucidate the spatial and seasonal association of fur seal distribution and ocean environments, we constructed statistical models to describe how potential prey distribution and oceanographic features influenced the fur seal spatial distribution during the wintering period. Fur seal distribution corresponded markedly to potential prey distribution, and they tended to aggregate along the narrow continental shelf that is the main geographic feature of this area, which is 2000 m deep and approximately 10 km from the coast. Walleye pollock [Gadus chαlcogrαmmα (Theragra chαlcogrαmmα)] and arabesque greenling (Pleurogrammus azonus), which are one of the main prey for fur seals, move to the shallow area to spawn on the continental shelf seasonally, so potential prey abundance could be higher in coastal areas than offshore. Moreover, the absence of a mesopelagic biotic community may be one of the main factors in the coastal distribution of the fur seal.     

Habitat configuration for an obligate shallow‐water delphinid: The Indo‐Pacific humpback dolphin,Sousa chinensis,in the Beibu Gulf (Gulf of Tonkin)

1. Habitat configuration is an important baseline to delineate protected area design, refine impact mitigation measures and define habitat protection plans for threatened species. For coastal delphinids, outlining their habitat configuration becomes a real challenge when faced with large distribution ranges that straddle international borders, leaving broad information gaps in uninvestigated areas.
2. This study projected likely habitats of Indo‐Pacific humpback dolphins, Sousa chinensis, in the Beibu Gulf (Gulf of Tonkin) based on occurrence data and remotely sensed oceanographic characteristics. Net primary productivity was derived to measure the ecosystem service of humpback dolphin habitats.
3. Bathymetry and chlorophyll‐a concentration are major variables contributing to humpback dolphin habitat configuration, which is characterized by shallow water depth and high primary productivity. Three major, likely habitats were identified in the northern Beibu Gulf from western Leizhou Peninsula to the China–Vietnam border, western Gulf of Tonkin from the Red River estuary to the central coast of Vietnam, and south‐western Hainan Island. Less than 9% of likely habitats are currently protected by marine protected areas.
4. Affinity to high primary productivity and shallow depths implies that prey abundance and foraging efficiency influence habitat selection by Indo‐Pacific humpback dolphins. Anthropogenic activities potentially altering oceanographic characteristics may impact regional marine ecosystem functions, and hence habitat configuration.
5. Habitat protection actions for Indo‐Pacific humpback dolphins include implementing coordinated and systematic surveys in major habitats, associating core habitat protection with protected area networks and maritime function zoning, ensuring ecosystem function integrity within major habitats, and reducing both explicit lethal impacts and implicit anthropogenic impacts from activities that change oceanographic features. The habitat protection plan should not only consider marine habitats, but also adjacent coastal landscapes and river catchments. This requires coordination, collaboration and information sharing between scientific research teams, government policy representatives, non‐governmental organizations, local communities and other interested stakeholders.

     

Distribution patterns of loliginid squid paralarvae in relation to the oceanographic features off the South Brazil Bight (22°–25°S)

Loliginid squids constitute marine resources of increasing importance in shelf ecosystems off the coast of South Brazil. However, the existing information and knowledge about the occurrence of early‐life stages and causes of distributional patterns are insufficient. Here, we have revisited Brazilian historical plankton samples obtained from 11 oceanographic surveys to identify paralarvae and their abundances over time. The study area and time period cover the region between Cabo de São Tomé (22°S) and Cananéia (25°S) at depths down to 200 m from 1991 to 2005. Of the 246 paralarvae quantified, ~50% were identified to the genus or species level, including Doryteuthis spp. (D. sanpaulensis and D. plei), Lolliguncula brevis and a single specimen of Pickfordiateuthis pulchella. Paralarval occurrence and abundance peaked in different areas and were associated with distinct oceanographic conditions: D. sanpaulensis occurred in the northern region associated with cold waters and upwelling events, D. plei occurred primarily in the southern region of the study area and in warmer waters, and L. brevis was found in shallow and low salinity waters in the estuarine region off the coast of Santos. Overall, the highest abundance of paralarvae occurred in the nearshore, northernmost areas during summer, and this can be associated with the observed retention mechanisms caused by local circulation, seasonal upwelling, the intrusion of nutrient‐rich waters, and spawning peaks. The present study provides new information and evidence for loliginid patterns in the area that may potentially be useful for better understanding the recruitment patterns and fishery assessments of squid populations.