First record of anomalous otoliths of Menticirrhus americanus in the South Atlantic

Sagitta otoliths are usually formed of calcium carbonate polymorphs as aragonite. The objective of this study was to verify which carbonate polymorph is predominant in the sagitta otolith of Menticirrhus americanus and check whether this pattern remains in otoliths with morphological alterations. Otoliths of M. americanus were obtained from five sites on the southeast‐south coast of Brazil (São Sebastião (SS) 23°45′S–45°24′O, n = 29; Cananéia‐Iguape Estuarine Complex (CI) 25°02′S–47°54′O, n = 30; Paranaguá Estuarine Complex (PEC) 25°28′S–48°20′O, n = 35; Itapoá (IT) 26°07′S–48°36′O, n = 31; Laguna (LA) 28°28′S–48°46′O, n = 13). The characterization of carbonate polymorphs of otoliths was performed through Raman spectroscopy, a photonic and non‐destructive technique that analyzes molecular vibrations induced by laser. We analyzed 138 pairs of M. americanus otoliths, of which eight otoliths from different pairs presented morphological alterations (SS n = 1, CEP n = 5, IT n = 1, LA n = 1). The Raman spectra show that normal otoliths, that is, without morphological alterations, presented only aragonite in their structure. Among the otoliths that presented morphological alterations, the Raman spectra allowed to identify in six otoliths the deposition of aragonite and in only two otoliths the deposition of vaterite (one specimen of the PEC and one of SS).     

Siberian and Russian sturgeon natal origin in South America: Fish farm or established population?

Sturgeon (Acipenser baerii and A. gueldenstaedtii) specimens, native to the northern hemisphere, were reported in different environments of the La Plata Basin (South America). The objectives of this study were to provide the first insights into the natal origin and habitat use of these sturgeon species in the La Plata Basin through geochemical analysis (⁸⁷Sr/⁸⁶Sr) of fin spines and to review historical catch reports. Spine core-to-edge ⁸⁷Sr/⁸⁶Sr ratios were measured by LA-MC-ICPMS. A Quadratic Discriminant Analysis model based on water ⁸⁷Sr/⁸⁶Sr baseline of the La Plata Basin was run to infer the natal origin. The isotopic profiles indicate a common origin, compatible with the location of the fish farms in the Uruguay Basin. The A. baerii isotopic time series suggested that the fish moved towards the Paraná Basin months before capture, while A. gueldenstaedtii would have survived a longer time (perhaps years). Seventeen reports of sturgeons were recorded and preserved in museum collections between 1998 and 2020. Sturgeons were collected from Río de la Plata Estuary, Paraná and Uruguay basins and Atlantic coastal lagoons. It is recommended to closely monitor sturgeon catches, paying special attention to the appearance of specimens of reproductive age, in order to generate management and management plans if necessary.     

Otolith Sr/Ca ratio complements Sr isotopes to reveal fish migration in large basins with heterogeneous geochemical landscapes

Environmental Biology of Fishes - The potential use of Sr/Ca and Ba/Ca ratios in fish otolith, as a complement to 87Sr/86Sr to study movements of Prochilodus lineatus, was evaluated in the La Plata...     

Reproductive Ecology of Pterapogon kauderni, an Endemic Apogonid from Indonesia with Direct Development

Pterapogon kauderni does not have secondary sexual dimorphism, and has an equal sex ratio (50.8% males:49.2% females). Females first mature at a length of about 34mm. Data from both laboratory-bred and wild-collected eggs and embryos are not consistent with the presence of differential reproductive allocation in this species. Analysis from clutches brooded by wild-collected males shows a significant intra-clutch and among-clutch variation in egg size. Mean individual egg size (diameter, volume, or weight) is not correlated with the size (standard length, head length, or lower jaw length) of the males brooding those eggs. P. kauderni has a lunar reproductive cycle, with a major spawning peak during full moon and a smaller peak during the last quarter. Similarly, it has a major juvenile release (settlement) peak at full moon, with a minor peak at new moon. However, one population, which is located in a site with distinct environmental conditions and which was sampled a year earlier, shows a different reproductive pattern, last quarter being the phase where most of spawn and release events take place.     

Trace metal contents in water and sediments in Samborombón Bay wetland,Argentina

Samborombón Bay is the most extensive myxohaline wetland of Argentina. This Ramsar site is considered a priority area for the conservation of biodiversity in the country. Numerous rivers and channels that drain the Pampean plain, such as the Salado River and the channels Lower Salado, 15, 9, A, 1, and 2, cross this wetland and flow into Samborombón Bay. Trace metal concentration (As, Cd, Cr, Cu, Mn, Ni, Pb, and Zn) in water and sediments were determined in low and high water periods. In the first case, contents were higher than the Guide Levels for the Protection of the Aquatic Biota (GLPAB) in most of the sampling stations. In high water period, only As and Zn were detected. Relevant physico-chemical parameters were analyzed by a principal component analysis (PCA). Trace metal concentrations in sediments suggest, as a whole, that this wetland has been so far exposed to low to moderate levels of anthropic influence. It must be emphasized however, that the presence of metals in both the water and sediments of this bay might have negative effects on the biota and on the regional trophic web.     

White mullet Mugil curema population structure from Mexico and Brazil revealed by otolith chemistry

The white mullet Mugil curema supports several fisheries in the neotropical region; nevertheless, the population structure is still elusive. The aim of this study was to assess the presence of adult management units and nursery areas from five sampling sites throughout the Gulf of Mexico and northern Brazil using otolith microchemistry. The Li/Ca, Na/Ca, Mn/Ca, Sr/Ca, Ba/Ca and Pb/Ca ratios were measured in otolith core (juvenile stage) and edge (adult stage) (N = 131) using laser ablation–inductively coupled plasma–mass spectrometry. Several ratios were significantly different between sampling sites for core and edge (P < 0.05). For otolith edge, permutational multivariate analysis of variance showed significant differences (P < 0.05) between all sampling sites from Mexico (except between Mecoacán and Tamiahua, P > 0.05) and between Mexico (pooled samples) and Brazil. Quadratic discriminant analyses showed jackknifed classification higher in the edge (66.6% and 99.5% for Mexico and Brazil plus Mexico, respectively) than in the core (46.3% and 76.5% Mexico and Brazil plus Mexico, respectively). The two cluster analyses based on the core microchemistry (Mexico and Brazil plus Mexico) produced three main clusters, which did not coincide with catchment areas. These results support the segregation of the M. curema adult life stages among several sampling sites from Mexico and Brazil; moreover, core analysis suggested that the nursery areas did not correspond to the capture sites or adults stocks.     

Fishes and environment in northwestern Argentina: from lowland to Puna

The fish fauna and its relationships with physiography and climate were studied in northwestern Argentina from 21°30′ S to 26°30′ S and 63°30′ W to 65°50′ W, an area about 10,276 km². Along a southeast–northwest gradient, the Chaco forest at low altitudes gives way to the Yungas cloud forest in highlands, and then, to an increasing desertic landscape, with xerophytic vegetation and scarce rainfall along the Grande River. Finally, extreme desert conditions prevail in the most northern part at the Puna plateau. Water chemistry was sampled from sites from 400 to over 3800 m a.s.l. In all 3278 fish specimens of 52 species were collected. Previous lists included 84 species. Only 19 were shared, meaning that 40 species are new for the area and/or particular localities, including 7 reports from Aguas Calientes. These results increase by one third the number of species in northwestern Argentina. The fish fauna was represented by eurytopic species of Paranensean genera as Astyanax, Bryconamericus and other characoids, mixed with locally distributed siluriforms. Under extreme climatic conditions, species of Trichomycterus predominate. Species assemblages show a combination of a large number of species typical of, sometimes endemic to or rather abundant in, the area, combined with a few species of Paranensean character. Fish assemblages were clearly defined by faunistic composition and distribution related with physiography and climate traits. A significant negative correlation is observed between both species number and abundance, and increasing altitude, and positive relationships exist with mean annual temperature and other climate traits. Diversity values (Shannon index) agree with the described pattern of increasing impoverishment of the fish fauna of northwestern Argentina, along gradients of increasing altitude and dryness and decreasing temperature.A first version of this paper was submitted at the XXVII Congress of the Societas Internationalis Limnologiae, Dublin, Ireland, 1998.