Otoliths are an excellent tool for analysing the pattern of habitat use between adults and juveniles and connectivity between fish populations. Larimus breviceps is a species belonging to the family Sciaenidae, which has an important role in the marine food chain, as it is one of the most abundant and frequent species in the bycatch of coastal shrimp fisheries in Brazil. The present study aimed at comparing the otolith shape of specimens collected in three different Brazilian coastal areas: Sergipe (SE), northeastern region; São Paulo (SP), southeastern region; and Paraná (PR), southern region. In a laboratory, 88 otoliths were extracted, photographed, and the contour was analysed by the wavelet method (32 from SE, 28 from SP, and 28 from PR). The otolith contours varied between sampling sites. Linear discriminant analysis correctly reclassified 60.23% otoliths by the sampled sites, with the best reclassifications occurring in SE (62.5%), followed by PR (60.71%) and SP (57.14%). Multivariate analysis of variance also evidenced significant differences in contours among the sampling sites (F = 2.3; P < 0.005). Thus, two morphotypes of otoliths were found for L. breviceps: one from Sergipe (northeastern Brazil) and the second one from southeastern–southern Brazil, indicating connectivity between the populations off São Paulo and Paraná, to be confirmed by future genetic studies.

The microcotylid Sciaenacotyle pancerii is a pathogenic monogenean infecting Argyrosomus regius, a candidate for species diversification in the Mediterranean aquaculture. Life-history stages of S. pancerii commonly co-occur in field infections, but to date, morphological data have only been provided for oncomiracidia and adults although identifying life-history stages can be useful in infection management. A total of 114 specimens of S. pancerii were analysed to characterize the developmental events and to assess morphological and morphometric variations before and after maturity. The post-larval development of S. pancerii is characterized by: expansion and bifurcation of the gut, loss of the larval haptor, protandrous development of the genitalia and vitellaria formation. The size variability of larval hooks, hamuli and germanium of S. pancerii is firstly reported and dimensional ranges of parasite body, haptor, testes, posteriormost clamps and eggs are widened. The size of most of the diagnostic features of S. pancerii significantly increases after parasite maturity and therefore, only those specimens with more than 116 clamps should be considered for minimising development-related variability in size. The high number of clamps, their fast development and the asymmetry in their size and arrangement suggest that S. pancerii may use a mixed attachment strategy between the closely related microcotylids and heteraxinids. This combination of features may be host related and linked to the gill structure of the sciaenid fish and the phylogenetic position of the genus Sciaenacotyle; distant from other microcotylids while close to heteraxinid species.

The aim of this study was to test the effective separation of shape indices of otoliths of three species belonging to the family Sciaenidae before and after in vitro digestion. We measured 328 sagittal otoliths and applied six shape indices. Before the experiment, the aspect ratio (otolith height/otolith length%), circularity, ellipticity and relative surface of the sulcus acusticus were suitable for differentiating the species of genera Paralonchurus and Stellifer. Among the species of Stellifer, the aspect ratio and rectangularity were suitable. Otoliths exposed to in vitro digestion showed no significant differences in their morphometry before and after the experiment. After in vitro digestion, the aspect ratio and circularity were effective in separating Paralonchurus and Stellifer. However, none of the indices used in the present study were efficient to separate otoliths of congeneric species after in vitro digestion.

Latitudinal patterns of composition, biogeographic affinity and indicators of taxonomic diversity are described for the by-catch fish community in five typical shrimping areas in the Mexican Pacific (Upper Gulf of California, Sinaloa-Nayarit, Jalisco-Colima, Michoacán-Guerrero and Gulf of Tehuantepec). The taxonomic composition included two classes, 20 orders, 65 families, 147 genera and 292 species. The family Sciaenidae was the best represented with 33 species, whereas at the genus level, Anchoa was represented with eight species. A high percentage of the species showed wide distribution ranges (30.2% for Cortez Province ~ Panamic Province; 21.3% for San Diego Province ~ Panamic Province); nevertheless, each ecosystem included a characteristic combination of species, apparently related to the physiographic conditions of the ecosystems. Species richness showed a pronounced decrease from the Upper Gulf of California, which has warm-temperate features, to the Gulf of Tehuantepec, which has tropical conditions; this is an opposite trend to that observed in the taxonomic diversity indicators, suggesting that a taxonomic redundancy was present in tropical areas and higher taxonomic diversity was present in the Upper Gulf of California, despite the lower species richness. This is explained by the prevailing environmental conditions and isolation processes generated during the formation of the Gulf of California.

A comparative analysis on various aspects of the reproductive biology of 7 Sciaenidae family species was done. In addition the reproductive parameters needed for stock assessment models were provided. The research covered the analysis of the duration of the breeding season and the estimation of reproductive variables such as size at maturity, fecundity and spawning frequency. When all species were considered together, some aspects of reproduction were similar, regarding the reproductive strategy; all species are batch spawners with indeterminate fecundity and an extensive reproductive season (approximately six months) except for Pogonias cromis, which showed a more limited spawning season (three months). With regard to reproductive potential, wide differences in fecundity values mainly due to the different sizes attained by each species were observed (range in batch fecundity values between 5000 and 2,800,000 hydrated oocytes). However, when relative fecundity was compared, average values were generally similar, ranging approximately between 150 and 200 hydrated oocytes per female gram. Pogonias cromis is the exception within this group, because the mean relative fecundity ranged between 75 and 98 hydrated oocytes per ovary-free female gram. This difference may be a consequence of the greater oocyte size reached by P. cromis eggs (1100–1400 μm) compared to the rest of sciaenid analysed (750–900).

Patterns of annual freshwater flows in the Murray River and recruitment of mulloway, Argyrosomus japonicus (Scianidae) were reviewed in terms of recent age structures and historical catches and CPUE. Age distributions from the nearshore marine fishery were dominated by the 1993 age class which comprised 35% and 41% of 2001 and 2002 catches, respectively. In 1993 annual freshwater inflow was 2.4 times the 25 year average. Freshwater inflow explained 28% and 35% of the variability in year class strength in the nearshore marine fishery in 2001 and 2002, respectively. Over 80% of the current South Australian commercial catch of mulloway comprises juveniles taken from the remnant estuary of the Murray River. Our results suggest that recent low levels of recruitment in South Australia's fisheries for A. japonicus may reflect low fresh water inflows since 1993. Since 2000, southern Australia has experienced the worst drought in recorded history and management strategies for this fishery must take into account effects of both environmental factors and fishing mortality on this vulnerable sciaenid population. We suggest that the population of A. japonicus located about the Murray River system is estuarine dependent, that the estuary provides important refuge for juveniles, and that strong year classes, or their absence, may be related to freshwater inflow to this environment. We also suggest that age distributions of this apex predator may provide an indicator of environmental health for the Murray River estuary.

Age and growth of the brown meagre Sciaena umbra (Sciaenidae) collected (n = 532) in the north-western Adriatic Sea was studied by means of transverse otolith sections. The maximum age estimated was 19 and 16 years for males and females, respectively. The length at age estimated for each sex indicated that females attain a larger size and grow slightly faster than males. Both marginal increment analysis and edge analysis confirmed that annuli are formed once a year, with opaque zones laid down in summer (June-July). Age readings were very precise, with a percentage agreement of 98% between readers and low values of the index of average percent error (0.9%) and coefficient of variation (1.3%). Von Bertalanffy growth function was fitted to age-length data, and growth parameters were estimated for males (L ∞ = 44.9 cm; k = 0.27,t 0 = −2.17 years) and females (L ∞ = 47.2 cm; k = 0.28, t 0 = -1.82 years). In both sexes of brown meagre, growth rate was high until they attain 2–3 years of age, i.e. at sexual maturity. Most of catches were obtained in late summer-early autumn. On the basis of present data, the sampled population of brown meagre mostly consisted of small fish younger than three years of age (about 90%). In addition, landings of this species in recent years largely decreased. As reported elsewhere in north-western Mediterranean, brown meagre stock in the Adriatic Sea showed clear signs of depletion, thus specific management measures for this species are urgently required.