Condition of 0-group and adult pouting, Trisopterus luscus L., along the Portuguese coast: evidence of habitat quality and latitudinal trends

The present study assessed condition of pouting ( Trisopterus luscus Linnaeus, 1758) in nursery areas and other coastal areas along the Portuguese coast using different indices. Condition factor Fulton's K, RNA : DNA ratio and total protein content were determined for 0-group pouting collected in three shallow nursery grounds. Adult pouting were sampled in 10 sites along the coast and Fulton's K, hepatosomatic index (HSI), total protein content and water content were determined as indicators of condition. For 0-group individuals, only total protein content showed significant differences among the sites, whereas in adults all the indices evaluated differed significantly among the sites. However, due to high RNA : DNA ratios it was considered that all investigated nursery areas provided suitable conditions for survival and rapid growth of early stages of T. luscus . Adult pouting were also considered to be in good physical and nutritional condition along the Portuguese coast, although better growth conditions seem to be provided in the warmer waters of southern Portugal, evidencing a latitudinal trend.     

Niche overlap between juvenile flatfishes, Platichthys flesus and Solea solea, in a southern European estuary and adjacent coastal waters

The distribution and abundance patterns as well as the feeding ecology of two flatfishes, Platichthys flesus (Linnaeus, 1758) and Solea solea (Linnaeus, 1758), were studied in the Douro estuary and adjacent coastal waters (Portugal) in order to evaluate the niche overlap between these species. Fish were collected during sampling surveys conducted every 2 months between November 2000 and March 2002 using a 12‐m otter‐trawl with 18 mm stretched mesh size, at 12 sites within the estuary and six sites in the adjacent coastal area. The highest densities of P. flesus were registered in the middle estuary; a peak density of 9.12 ind 1000 m^?2 was obtained in October 2001. Solea solea densities were low compared with P. flesus; the highest values were also recorded in the middle estuary in October 2001. For both species, the proportion of juveniles was above 90% within the estuary. Highest densities of P. flesus and S. solea were recorded at sites with low water depth and high densities of crustaceans and polychaetes, the main food items in the diet of these species. High values of spatial and diet niche overlap were found between these two flatfishes (0.97 and 0.92, respectively).     

Distribution and dietary relationships of the Japanese temperate bass Lateolabrax japonicus juveniles with two contrasting copepod assemblages in estuarine nursery grounds in the Ariake Sea, Japan

Early juvenile Japanese temperate bass Lateolabrax japonicus samples were collected during four cruises to study the spatial and temporal patterns of distribution and feeding habits of the fish in Chikugo estuary, Ariake Sea, Japan. Gut contents were studied by separating, identifying and counting the prey organisms. Plankton samples were collected during each cruise to study the numerical abundance of copepods in the water. Copepod dry biomass and gut content dry mass were estimated. Juveniles were distributed over wide estuarine areas in salinities ranging from as low as 0·37 to as high as 28·81. Considerable spatial and temporal variations were observed in the copepod distribution in the environment and in the food habits of the fish. Two distinctly different copepod assemblages were identified along the estuary: one in the upper river, dominated by a single species Sinocalanus sinensis, and the other a multi‐specific assemblage in the lower estuary dominated by common coastal copepods such as Acartia omorii, Oithona davisae, Paracalanus parvus and Calanus sinicus. The gut content composition corresponded strongly with the copepod composition in the environment, i.e. a single species (S. sinensis) dietary habit at the upper river and a multi‐specific dietary habit dominated by the common coastal copepods in the lower estuary. Ivlev's electivity index showed that the fish strongly preferred larger copepods and avoided smaller ones. Higher dry biomass of copepods in the water as well as higher dry masses of the gut contents were recorded in the low‐to‐medium saline upper river areas, indicating that these areas are of particular importance as nursery grounds for the juvenile Japanese temperate bass. It was speculated that ascending to the upstream nursery areas to utilize S. sinensis, which is the single dominant copepod in these areas, is one of the most important survival strategies of the Japanese temperate bass juveniles in the Chikugo estuary.     

Importance of the upper estuary as a nursery ground for fishes in Ariake Bay,Japan

To examine the importance of the upper estuarine areas of Ariake Bay as a nursery ground for fish, assemblages of larvae and juveniles were compared among various aquatic habitats. The upper estuaries of the bay (the Rokkaku and Hayatsue estuaries) are brackish, highly turbid waters with high tidal velocities, and differ substantially from the Isahaya area, which has been separated from the bay by a man-made dike, to the middle estuary (the Kikuchi estuary). Abundances of larvae and juveniles were higher in the estuaries than in the open bay and Isahaya areas. Abundant species in the upper estuaries were similar to each other, but differed from those of the middle estuary. This was primarily due to larvae and juveniles of fishes that occurred almost entirely in the upper estuaries, such as Acanthogobius hasta, Boleophthalmus pectinirostris, Coilia nasus, Cynoglossus abbreviatus, Nibea albiflora, Odontamblyopus lacepedii, Trachidermus fasciatus and Tridentiger barbatus. These results suggest that the upper estuaries play an important role as nursery grounds for fishes.     

Nutritional condition, starvation status and growth of early juvenile Japanese sea bass (Lateolabrax japonicus) related to prey distribution and feeding in the nursery ground

The nutritional condition and protein growth rates of Japanese temperate bass larvae and juveniles were studied in relation to prey distribution and feeding habits in the nursery grounds in Chikugo estuary, Ariake Sea, Japan. Samples were collected from a wide spatial area covering the nursery grounds of the fish in March and April 2003. Food habits of the fish were analyzed by examining the gut contents. Fish condition was evaluated by using RNA/DNA ratio and other nucleic acid-based indices and protein growth rates. The nucleic acid contents in individually frozen larvae and juveniles were quantified by fluorometric method. Two distinguished feeding patterns, determined by the distribution of prey copepods, were identified along the nursery ground. The first pattern showed the dependency of the fish on the calanoid copepod Sinocalanus sinensis, which was the single dominant prey in low saline upper river areas and the second pattern involved a multi-species dietary habit mainly dominated by Acartia omorii, Oithona davisae and Paracalanus parvus. Values of RNA, DNA, total protein, growth rates and for all the nucleic acid-based indices were higher in upstream areas than in the downstream areas. The proportion of the starving fish was higher in the downstream areas than in the upstream areas. Condition of juvenile sea bass was not equal throughout the nursery grounds; fish in the upper river were in better condition than those in the lower estuary. We speculated that utilization of S. sinensis, which appears a suitable prey item and provide a better foraging environment in the upstream nursery ground, is one of the key factors for early survival and growth of Japanese temperate bass larvae and juveniles in the Chikugo estuary.     

Distribution and diet of the roughskin sculpin, <Emphasis Type="Italic">Trachidermus fasciatus</Emphasis>, larvae and juveniles in the Chikugo River estuary,Ariake Bay,Japan

Larvae and juveniles of the roughskin sculpin Trachidermus fasciatus were collected during four cruises in March and April 2001 to study the distribution and diet of the fish in the Chikugo estuary in the northern Ariake Bay, Japan. Sampling was conducted at seven stations covering an area approximately 30 km in length along the estuary, with salinity ranging from nearly 0 to about 30 PSU. Gut contents were analyzed by separating, identifying, and counting the prey organisms. Plankton samples were collected during each cruise to study the numerical composition and abundance of copepods in ambient water. A total of 1790 larvae and juveniles of T. fasciatus were collected; they were distributed in the five uppermost stations, covering approximately 20 km and ranging in salinity from 0.4 to 27.4 PSU. The fish fed almost exclusively on a single calanoid copepod species, Sinocalanus sinensis, which was numerically the most abundant in the ambient water at the upper part of the Chikugo River. At the lower part of the river, the fish positively selected S. sinensis while negatively selecting other species. T. fasciatus larvae experienced a high proportion of empty guts and low feeding intensity at around 9.0 mm body length, which appears to be associated with commencement of exogenous feeding. The proportion of empty guts reduced sharply at subsequent stages and was accompanied by an increase in feeding intensity. The oligohaline and mesohaline areas are important nursery grounds, and S. sinensis is an important prey copepod species for the larval and juvenile T. fasciatus in the Chikugo estuary.     

Biological availability and humic properties of dissolved organic carbon in Lake Balaton (Hungary)

The nursery role of the Mondego estuary for marine fish species was studied between June 2003 and May 2004. The spatial and temporal distribution and abundance patterns of 0-group Dicentrarchus labrax (Linnaeus, 1758), Platichthys flesus (Linnaeus, 1758) and Solea solea (Linnaeus, 1758) were analyzed based on monthly sampling surveys in five stations along the estuarine gradient. Fishing took place during the night at low water of spring tides, using a 2 m beam trawl. The spatial patterns of estuarine colonization were different according to species. D. labrax showed a wider distribution, but the main nursery ground was the same as for S. solea. Highest densities of S. solea juveniles were found in oligohaline areas, with muddy bottoms and high benthic invertebrates availability, while P. flesus occurred mainly in the sandy uppermost areas. D. labrax was found in both these areas. Fish abundance in the estuary mainly reflected seasonal changes.     

The fish assemblage of the Mondego estuary: composition,structure and trends over the past two decades

The fish assemblage of the Mondego estuary was studied from June 2003 to May 2004. Five areas with different environmental conditions were sampled monthly, using a 2 m beam trawl (5 mm mesh size at the cod end). To complement information, sampling was also performed, seasonally, using a 7 m otter trawl with a 10 mm mesh size. Thirty-two species were identified. Dicentrarchus labrax, Pomatoschistus microps, Pomatoschistus minutus, Solea solea, Platichthys flesus and Diplodus vulgaris were the most abundant species. Marine juvenile migrants had the highest number of species, thirteen, followed by estuarine residents with eight species. Marine species that use the estuary as nursery grounds were the most abundant in terms of density and biomass. In spring and summer, juveniles occur in the upper, oligohaline areas, but afterwards, in autumn and winter, they tend to disperse to the middle and lower areas, with higher marine influence. Comparing the results obtained in this study with those reported in the early 1990’s, a marked decrease in species richness can be noticed, which is probably due to anthropogenic factors, namely an increase in depth of the main channel and intense euthrophication processes in the middle and upper areas.     

Patterns of abundance and size structure in the blue groper, Achoerodus viridis (Pisces, Labridae): evidence of links between estuaries and coastal reefs

Linkages between estuarine nursery areas and coastal reefs are thought to be important for sustaining populations of some reef fishes. Patterns of abundance and size structure in the blue groper, Achoerodus viridis (Pisces: Labridae), were documented at sites extending from sheltered reefs and seagrass, Zostera capricorni, habitats, in shallows of estuaries, to adjacent exposed reefs in New South Wales, Australia. Numbers of juvenile fish (< 200 mm SL) decreased from shallow to deep areas of reef within a site and from inner to outer estuarine sites within two estuaries. Increased numbers of large fish (> 400 mm SL) were found on the more exposed coastal reefs. These patterns were consistent over the 21/2 year study (May 1991–December 1993). Recruits were found in both seagrass and rocky reef habitat, and showed similar patterns of abundance to juveniles. Recruitment of A. viridis to seagrass habitat occurred in distinct seasonal pulses each year; peak recruitment occurred in September and October of each year. Patterns of abundance and size structure were consistent with a model of estuarine recruitment and movement to the open coast, but alternatives, such as differential mortality, could not be discounted.     

Geographical distribution and abundance of postlarval and juvenile Pleuragramma antarcticum (Pisces,Notothenioidei) off the Antarctic Peninsula

Summary The early life history of Pleuragramma antarcticum off the Antarctic Peninsula is described from extensive material collected during four expeditions between 1975/76 and 1982 by means of an RMT 1+8. Postlarvae occurred frequently on the northern continental shelf in February and March except during the 1977/78 season when they were almost absent. Abundance varied mainly between 1.8 and 14.7 postlarvae per 10³ m³ with maxima between 32.6 and 143.3 per 10³ m³. Juveniles were less abundant with 0.1–4.9 and maxima between 9.8 and 28.3 per 10³ m³, but formed a consistent, predominant proportion (83–97%) of the pelagic juvenile fish fauna throughout the years of the study. They were distributed over the whole Bransfield Strait and adjacent waters in the top 200 m. Postlarvae and juveniles showed different patterns of vertical distribution; more than 70% of postlarvae occurred in the top 135 m of the water column whereas 83% of juveniles were encountered between 70 and 200 m with increasing abundance towards the lower depth. Three length groups were identified corresponding to age groups 0, 1, and 2. Hatching was estimated to occur in December. Postlarval distribution patterns and the prevailing transport of water masses suggest that coastal waters south of the tip of the Antarctic Peninsula and in the north-eastern Bellingshausen Sea are probable spawning areas. The Bransfield Strait and adjacent waters represent nursery grounds for the early stages of P. antarcticum from these sites.     

Trophic ecology of juvenile bull sharks (Carcharhinus leucas) in the Coyote estuary,Costa Rica

Bull shark (Carcharhinus leucas) is a near-threatened elasmobranch species capable of moving between the fresh and salty waters of tropical and subtropical coastal areas, for which we still lack important ecological information. During their first years of life, bull sharks use estuarine systems as nursery areas, making them highly susceptible to environmental and anthropogenic pressures. We studied the trophic ecology of juveniles found in the Coyote estuary, a potential nursery area in Costa Rica, to understand the potential impact of further bull shark declines and gain knowledge that could aid in their conservation. We analysed the trophic ecology of juvenile bull sharks [81–103 cm total length (TL)] in the Coyote estuary, Costa Rica, using stable isotopes of δ¹⁵N and δ¹³C. Since one problem using this technique in juveniles is the confounding effect of the maternal signature, we sampled different tissues (muscle and plasma), verified the status of the shark's umbilical scar and identified the size at which the isotope signature is a result of the animal's current diet. The isotopic values of the muscle tissue reflected the maternal isotopic signature. In contrast, plasma values reflected the diet of juvenile bull sharks >95 cm TL and with a closed umbilical scar. Juvenile bull sharks fed primarily on teleost fishes of the order Anguilliformes and Siluriformes, and have a high trophic position (≥4.0) in the Coyote estuary. Our findings suggest that this estuary is an important feeding site for juvenile bull sharks of the Pacific of Costa Rica. Thus, the protection of essential habitats such as the Coyote estuary will benefit not only bull shark conservation, but also the conservation of an array of fish species that also use this habitat as a rookery, many of which are of commercial interest.     

Population demographics of Palaemon peringueyi (Macpherson 1990) (Decapoda: Palaemonidae) in a small intermittently open Eastern Cape estuary

The population demographics of the caridean shrimp Palaemon peringueyi was investigated monthly at four sites over a period of one year in the small, intermittently-open Grants River Estuary situated on the south-east coastline of southern Africa. Mean total abundance and biomass of P. peringueyi ranged between 0 and 23.2 ind m^?2 and 0 and 2.3mg wwt m^?2, respectively. A peak in its abundance coincided with a breaching event that occurred in December 2004, and could be attributed to the mass recruitment of juveniles (carapace length <9mm) into the estuary. Minor peaks in abundance were also associated with marine waters overtopping the sandbar that separates the estuary from the marine environment. The highest biomass values were recorded when the estuary was separated from the sea. Maximum abundance and biomass values of P. peringueyi were generally recorded in the middle reaches of the estuary where extensive beds of submerged vegetation, mainly Potamogeton pectinatus, predominated. Pearson correlation analysis indicated that the total abundance of P. peringueyi was significantly correlated (r = 0.49; p < 0.05) to percentage cover of submerged vegetation. The spatial pattern in abundance and biomass values of the shrimp is thought to reflect the availability of refuge areas against predation. A distinct spatial pattern in the community structure of the shrimp was evident, with juveniles numerically dominating the samples in the lower reaches of the estuary, while mature females predominated in the upper reaches of the system. In the middle reaches, the community comprised both juveniles and adults.     

Ontogenetic habitat preferences of the narrownose smooth-hound shark, Mustelus schmitti, in two Southwestern Atlantic coastal areas

The aim of this study was to determine the ontogenetic habitat preferences of the narrownose smooth-hound shark, Mustelus schmitti, in Río de la Plata and El Rincón coastal areas. There, canonical correspondence analyses of fishery research survey data showed that M. schmitti ontogenetic stages were differentially affected by depth, temperature and salinity. Neonates and juveniles were more abundant and remain in nearshore waters, suggesting the presence of nursery areas in which food availability and environmental conditions allow a faster growth. Adults M. schmitti presented different environmental associations mainly associated with depth and temperature. During non-reproductive season they were associated with deeper coastal waters. With the arrival of the reproductive season, adults migrate from deep to nearshore waters and show sexual segregation associated with pre- or post-mating behaviors. Hence, the year-round presence of neonates and juveniles and the seasonal occurrence of adults in nearshore waters make this habitat essential to M. schmitti population dynamics since key ontogenetic stages will be vulnerable if a direct impact occurs there.     

The mysid-feeding guild of demersal fishes in the brackish zone of the Westerschelde estuary

The demersal fish fauna of the mesohaline zone of the Westerschelde estuary (south-west Netherlands) was sampled intensively in the period 1990–1992. Almost 500 beam trawl samples were taken in both subtidal (330 samples) and intertidal (144 samples) habitats. These yielded 44 fish species, mostly as juveniles. The area functioned as a nursery for several demersal fish species, and harboured large populations of hyperbenthic mysids. Three gobies, three flatfish, one clupeoid and one gadoid dominated the fish fauna, while three mysid species were important components of the holohyperbenthos. From c. 1500 stomach contents of 25 fish species, 44 prey species were identified, the most abundant of which were also common in the hyperbenthal. The demersal fish community consisted of a group that foraged subtidally on fast-moving epi-and hyperbenthic prey (for example gadoids, gobies and clupeoids) and a group that foraged on slow-moving or sessile endobenthic organisms, mainly in intertidal areas (for example most flatfish species). Mysidacea occurred in >50% stomachs analysed and were taken as prey by 19 of the 25 fish species. Mysids were most important in the diets of Pomatoschistus minutus, P. lozanoi, Trisopterus luscus and Merlangius merlangus, and were present in appreciable numbers in Pleuronectes flesus, Trigla lucerna, Clupea harengus and Pleuronectes platessa. These species fed mainly on the brackish water endemic Neomysis integer. Mesopodopsis slabberi (present in 35% of the gobiid stomachs) and Gastrosaccus spinifer(present in 25% of the gadoid stomachs) were of secondary importance. P. minutus and T. luscus showed a diet shift from calanoids (Eurytemora aYnis and Temora longicornis) to mysids at L_S of 30 and 50 mm, respectively. Only 1% of the standing stocks of the N. integer and M. slabberi populations was removed by the local demersal fish community, so top–down control of mysid populations in estuaries seems unlikely.     

Species composition and dynamics of larval and juvenile fishes in the surf zone of Mauritius

The importance of the surf zone as a nursery ground for larval and juvenile fishes has been widely recognized, however the zone has yet to be studied in Mauritius. Recently, the coastal area of the island has been increasingly affected by human activities, especially by tourism. We collected fish samples with a hand pulled seine net during the period of August 2001 to March 2003 to clarify the fish fauna and the dynamics of fishes in the surf zone. Two sampling sites adjacent to river mouth areas and one sampling site adjacent to a mangrove area were selected for comparison of fish fauna in relation to environmental conditions. A total of 9,429 fish larvae and juveniles, representing at least 112 species from 48 families were collected. The abundant species were hardyhead silverside, Atherinomorus lacunosus, bluespot mullet, Valamugil seheli, and Ambassis spp., each contributing 16.2, 12.4, and 11.8% of the total number of individuals, respectively. Estuarine species dominated in the surf zone adjacent to the river mouth areas. Species composition and diversity changed seasonally. The number of fish increased during the rainy season. Species diversity increased at the turn of the seasons from the dry season to the rainy season. We conclude that species composition in each site was affected by environmental factors, such as the scale of the flux from the rivers, which is related to the precipitation. The results indicated that freshwater from the river is a trigger to aggregate larvae and juveniles in the surf zone.     

Estuarine colonization, population structure and nursery functioning for 0-group sea bass (Dicentrarchus labrax), flounder (Platichthys flesus) and sole (Solea solea) in a mesotidal temperate estuary

The function of the Mondego estuary as a fish nursery habitat was investigated from June 2003 to June 2004 by comparing the timing of estuarine colonization with juveniles of sea bass Dicentrarchus labrax, flounder Platichthys flesus, and sole Solea solea, while also analysing their population structure, growth and diet composition. Differences in the onset of estuarine colonization were observed, since sole juveniles were the first to enter the estuary (in January), followed by flounder in April and sea bass in June. The estuarine population of these species consisted of several age‐groups, although the majority of individuals belonged to age‐groups 0 and 1. The growth rates determined for 0‐group fish were within the range of those reported for other European estuarine systems. Some differences were also recognized regarding the timing of estuarine colonization and the length of the growing season. Diet of 0‐group sea bass consisted mainly of Crustacea, Polychaeta and Mollusca. Flounder juveniles fed chiefly on Amphipoda (especially Corophium spp.), with Polychaeta, Isopoda and Decapoda also being common prey. The diet of 0‐group sole was dominated by Polychaeta, with Amphipoda, Mollusca and Decapoda ranking highest, with other important benthic organisms also being present. Dietary overlap among these species was relatively low.     

Distribution patterns of the fish assemblage in the Mamanguape River Estuary,North-eastern Brazil

The Mamanguape River Estuary was studied along a continuum ranging from shallow sandstone reefs adjacent to the river mouth up to the limit of influence of seawater, the upper portions of the estuary. Fish samples were gathered using three types of nets along 17 sample sites, grouped in four regions according to salinity range (reefs and low, middle and upper estuaries), to seasonality (dry and rainy seasons) and to habitat usage (marine visitor, marine estuarine-opportunist, marine estuarine-dependent, estuarine resident and estuarine &; marine). Differences were found in the fish assemblages along the estuarine-reef gradient, with most species (n?=?30) being considered marine, estuarine-opportunists or estuarine-dependent, according to its abundance and distribution. A low number of species (n?=?11) were considered estuarine residents. Some species exhibited significant differences in spatial distribution pattern, in which juveniles and adults predominated in different portions of the estuary, suggesting an ontogenetic migration both in relation to the adjacent reef area and across estuarine regions. Several species were newly recorded in the Mamanguape Estuary: Anchoa spinifer, Halichoeres poeyi, Hyporhamphus roberti, Scomberomorus cavalla, Sphyraena barracuda and Ocgocephalus vesperilio.     

Origin here,impact there—The need of integrated management for river basins and coastal areas

This study highlights the effect that estuarine polluted waters may have on adjacent coastal waters and the need of an integrated management of the coastal area. Pollution of land-to-sea water plumes varies spatially and temporally, being difficult, costly and time consuming to determine. However, the reduction in water quality of both estuarine and coastal environments and the consequent degradation of its biological communities is at issue. Chlorophyll-a analysis from water and stable nitrogen isotopic analysis (δ¹⁵N) from opportunistic macroalgae Ulva species were respectively used as proxies to detect phytoplankton proliferation and nitrogen related nutrient fluxes in the water. These analytical techniques were combined with the use of three-dimensional hydrodynamic models, and revealed to constitute reliable early warning instruments, able to identify coastal areas at risk, and supporting an integrated management of coastal and river basin areas. The approach detected synchronized δ¹⁵N signal variations along time between estuarine sites (Mondego estuary, Portugal) and nearby adjacent coastal shore sites (NE Atlantic coast). The higher values recorded by macroalgal tissues’ δ¹⁵N signals, which occurred simultaneously to higher chlorophyll-a values, were linked to the anthropogenic contamination of the water, probably related with the Mondego valley land use patterns throughout the year (reflecting the opening of sluices that drain agriculture fields). Modeling scenarios point to a Mondego’s influence that is able to reach its adjacent coastal shores in about 7 km from its river mouth. The methodology used here is replicable elsewhere and allowed to track nutrients from the source, inside the estuary, until the final area of impact, where primary producers may use those for growth, and to define vulnerable areas on adjacent coastal zones.     

A nursery Area for Sharks and Rays in Northeastern Brazil

Synopsis Elasmobranch nurseries are habitats where females give birth to their young and juveniles spend their early life history. Hypotheses concerning nurseries suggest that these provide the young a better source of food and protection against predation, however the degree of exposure to predatory risk in nursery areas vary. According to Branstetter hypothesis, slow growing species are either born at relatively large sizes or use protected nursery grounds, whereas faster growing species tend to rely more on growth rates than others factors. Primary nurseries are habitats where parturition occurs and in which the young live for a short time and secondary nurseries are habitats in which juveniles are found after leaving the primary nursery and before reaching maturity. Rhizoprionodon porosus and Carcharhinus acronotus use coastal waters off Cai?ara do Norte as both primary and secondary nurseries, while Carcharhinus limbatus makes use of the area as a seasonal primary nursery in late spring and early summer. C. falciformis apparently makes use of the end of inner continental shelf and the outer continental shelf as a primary nursery. Gymnura micrura, Rhinobatos percellens and Narcine brasiliensis makes use of coastal and turbid waters of region as both primary and secondary nurseries throughout the year, while Dasyatis guttata utilizes the area as a primary nursery. Aetobatus narinari and Rhinoptera bonasus, although caught in lesser number, appear to use the region as both primary and secondary nurseries and only primary nursery respectively. Dasyatis marianae (endemic from Northeastern Brazil) may use coastal sandbanks as a primary nursery, while Dasyatis Americana apparently exploits waters about 10 – 20 m in depth with rocky reef substrate only as secondary nursery. There was a measurable degree of temporal and spatial separation among sharks’ species, which may effectively create separate ecological niches, whereas among rays, with the exception of the stingray D. marianae, a spatial and temporal overlaps were observed. The Branstetter’s hypothesis was supported.     

Habitat specific growth rates and condition indices for the sympatric soles Solea solea (Linnaeus, 1758) and Solea senegalensis Kaup 1858, in the Tagus estuary, Portugal, based on otolith daily increments and RNA-DNA ratio

Habitat specific growth rates and condition indices were estimated for Solea solea and Solea senegalensis, in two nursery areas within the Tagus estuary, at the end of the estuarine colonization process, in 2005. While in the uppermost nursery area the two species of sole live in sympatry, in the lower nursery only S. senegalensis is present. Daily increments of left lapillar otoliths were used to estimate age (in days) and determine growth rates (mm per day). Condition indices were assessed through RNA‐DNA ratio in muscle samples. Growth rates were higher for S. senegalensis (0.970and 1.180 mm per day in nursery A and B, respectively) than for S. solea (0.767 mm per day in nursery A). Growth rates of S. senegalensis from the uppermost nursery area were lower when compared to those obtained for the other nursery. The RNA/DNA condition index followed the general trend given by the growth rate estimates, i.e. values were higher for S. senegalensis than for S. solea. However, no significant differences were detected in S. senegalensis from the two nurseries. Larger variations in salinity (10‰ amplitude in the uppermost nursery vs 0.2‰ in the lower nursery) and highest pollution loads may be important factors lowering the habitat quality of the uppermost nursery in comparison to the lower nursery. The use of growth rate estimates based on otolith readings and the RNA/DNA index as tools for habitat quality assessment was discussed.