Alejandra V. Volpedo

Ecomorphological patterns of the sagitta in fish on the continental shelf off Argentine

Abstract Morphology and morphometry of the sagittae otolith were studied in fish associated with different substrates. The shape, margins and rostrum of three groups of otoliths from several species were analyzed: group 1 (fish associated with soft substrates, N =10 species), group 2 (fish associated with hard substrates, N =10 species) and group 3 (pelagic fish, not associated with the bottom, N =6 species). E and R indexes were calculated for each species. The value of E =maximum width of the sagitta (WO)/maximum length of the sagitta (LO)%, expresses the relative tendency in the shape otolith (from circular to elongate). The value of R =length of the rostrum (LR)/LO%, expresses the percentage in the total length of the otolith that corresponds to the rostrum. The sagittae of group 1 were circular or polygonal with rounded borders. The rostrum can be absent or poorly developed. The sagittae shape of group 2 was elongated, with ornamented borders and a rostrum. The sagittae of group 3 possessed a prominent rostrum, a deep V-shaped cisure and ornamented borders. Statistical analysis showed no significant differences in the E index of groups 1 and 2, while R values of the three groups were significantly different. These results were compared with 80 other species, belonging to 12 families, from the publisher literature. E and R values could be used to characterize the sagittae of the marine fish and could be considered a useful tool for fish ecology studies.

Heavy metals and trace elements in muscle of silverside (Odontesthes bonariensis) and water from different environments (Argentina): aquatic pollution and consumption effect approach

The concentrations of As, Ag, B, Ba, Bi, Ca, Cd, Co, Cr, Fe, Ga, Hg, K, Li, Mg, Mn, Mo, Na, Ni, Pb, Rb, Sb, Se, Sn, Sr, Te, Ti, U, V and Zn were determined in water and silverside (Odontesthes bonariensis) muscle samples from four important commercial fishing sites (Argentina) by ICPMS. Trace element concentrations in water with well-documented human health effects were above the recommended maximum levels established by Argentinean and international guidelines for the aquatic biota protection in three sampling sites (e.g. As: 28.4-367 μg L(-1); Cd: 0.17-1.05 μg L(-1); Hg: 0.07-0.63 μg L(-1); Zn: 71.3-90.0 μg L(-1)). High concentrations of As, Hg and Pb (0.03-0.76; 0.03-0.42 and 0.04-0.19 mg kg(-1) wet weight, respectively) were found in silverside muscle. Fishing communities associated with contaminated environments are likely to have higher consumption rates and are thus more likely to be exposed to higher concentrations of the toxic elements (As, Hg and Pb).

Use of otolith strontium:calcium ratio as an indicator of seasonal displacements of the silverside (Odontesthes bonariensis) in a freshwater) marine environment

Strontium:calcium (Sr:Ca) ratios were measured in sagittal otoliths of silverside (Odontesthes bonariensis) from a freshwater-marine environment (ParanaRiver Delta and Ro´o de la Plata River, South America) in order to understand its seasonal movements. Conductivity was recorded and the water Sr:Ca ratio was determined by inductively coupled plasma-atomic emission spectrometry (ICP-OES). A calibration curve of water Sr:Ca ratio versus otolith Sr:Ca ratio from four isolated lentic water bodies was made to predict silverside displacements in the lower section of the Plata Basin during summer (lotic water bodies). Otolith Sr:Ca ratio of silversides from the ParanaRiver Delta was associated with the conductivity of water at the locations where the sample was collected. According to this association and the obtained results in the calibration curve, the silversides were displaced from zones where conductivity was 7.45 (mScm � 1 ), corresponding to the water Sr:Ca ratio in the outer section of the Ro´o de la Plata River (1.92mmolmol � 1 ). The high values of otolith Sr:Ca ratio found for some fish may indicate that during summer they moved from estuarine waters where salinity increases gradually to the Argentinian Sea. Additional keywords: estuarine, Odontesthes bonariensis.

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.

Use of lapillus otolith microchemistry as an indicator of the habitat of Genidens barbus from different estuarine environments in the southwestern Atlantic Ocean

The marine catfish Genidens barbus is an anadromous species from South America. The aim of the present study was to evaluate the use of lapillus otolith microchemistry (Sr:Ca; Ba:Ca and Mg:Ca ratios) as an indicator of changes in habitat use and identify the potential breeding areas and fish stocks of G. barbus populations from the Plata Basin (Paraná River Delta and De la Plata River estuary-Argentina) and Lagoa dos Patos coastal lagoon (southern Brazil). Sr:Ca, Ba:Ca and Mg:Ca ratios were measured in the core area (inner 4 rings) and external area (outer 3–4 rings) of the otoliths by ICP-OES. The Sr:Ca ratio tended to be higher in the otolith external area than in the core area, while the Ba:Ca ratio followed the opposite pattern. This suggests the displacement of fish toward higher salinity areas. The Sr:Ca, Ba:Ca, Mg:Ca ratios in the core and external areas of the otoliths from the Plata Basin differed significantly from those of the otoliths from Lagoa dos Patos. This may indicate the occurrence of two different breeding sites and at least two fish stocks in the study region.

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 34 mm. 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.

A Review of the Application of Otolith Microchemistry Toward the Study of Latin American Fishes

ABSTRACT In developed countries, otolith microchemistry has been used for more than three decades for studies of life history, migration, and environmental ecology of fish stock of commercial importance. Although Latin America produces 16% of the annual fish capture, most of their fishery resources have not been well studied and handled. Modern methodologies related to microchemistry have not been applied to the underdeveloped countries of Latin America due to its high cost. In the last decade, there have been several studies on Latin American resources, carried out mainly by first world countries. Currently, some regional economies are strong and stable enough to ensure the training of specialized human resources and to generate opportunities for the exchange of projects and acquisition of state-of-the-art technology. In this work, all available literature associated to Latin American resources in relation to the use of otolith microchemistry has been reviewed. The use of different methodologies in the region in relation to global trends has been discussed. In addition to that, the extent of collaboration between underdeveloped and developed countries has been evaluated. This review shows a promising future in the application of otolith microchemistry to study biology of fishes, which will impact on the medium and long term to ensure the sustainability of certain resources and, therefore, the strengthening of regional economies.

Assessment of the morphometry of saccular otoliths as a tool to identify triplefin species (Tripterygiidae)

In the present work we describe nine saccular otolith morphometric indices (circularity, rectangularity, aspect ratio, percentage of the otolith surface occupied by the sulcus, percentage of the sulcus length occupied by the cauda length and ostium length, otolith length relative to the length of the fish, rostrum aspect ratio and percentage of the rostrum length occupied by the otolith length) of 41 species of the Tripterygiidae family collected mainly from New Zealand, Australia, Chile, South Africa, Mediterranean Sea and North America. The principal component of analysis showed that the indices that best explain the variability between species were related to sulcus and rostrum morphometry. According to cluster analysis, otolith morphometry could reflect the diversity of microenvironments for some genera such as Notoclinops and Forsterygion , while this does not happen to genera like Enneapterygius and Ruanoho . The discriminant analysis showed that the species Helcogrammoides cunninghami, Karalepis stewarti, Lepidoblennius haplodactylus, Notoclinus compressus, Ucla xenogrammus can be discriminated by using the morphometric indices. Two new indices related to the sulcus that were of great value for the discrimination of these species are described for the first time. This information will be a useful tool for palaeontological, taxonomic and trophic ecology studies.

Use of otolith strontium:calcium and zinc:calcium ratios as an indicator of the habitat of Percophis brasiliensis Quoy & Gaimard, 1825 in the southwestern Atlantic Ocean

Fish were collected in three sampling sites: Argentine-Uruguayan Common Fishing Zone (AUCFZ), El Rincon (ER) and San Matias Gulf (SMG). The otolith Sr:Ca and Zn:Ca ratios were determined by ICP-OES and EDTA volumetric method. The otolith Sr:Ca ratio was similar in the three sampling sites, while the Zn:Ca ratio was significantly higher in AUCFZ than in ER and SMG for all age groups. The discriminant analysis showed an association between the otolith Sr:Ca and Zn:Ca ratios from ER and SMG. Present results suggest the potential occurrence of two fish stocks of

Nursery areas and connectivity of the adults anadromous catfish (Genidens barbus) revealed by otolith-core microchemistry in the south-western Atlantic Ocean

The anadromous catfish, Genidens barbus, is a commercial and vulnerable species from South America. The aims of the present study were to assess whether the nursery areas can be discriminated by using microchemical signatures of lapillus otoliths, to assess the accuracy of classifying fish in relation to natal nursery area and to discuss the possibility of existence of homing behaviour. Thus, the otolith-core chemical signatures (barium (Ba):calcium (Ca), lithium (Li):Ca, magnesium (Mg):Ca, manganese (Mn):Ca, strontium (Sr):Ca, and zinc (Zn):Ca ratios) of adult fish were compared among different estuaries (De La Plata River in Argentina, and Patos Lagoon, Paranagua Bay and Guanabara Bay in Brazil). PERMANOVA analysis showed significant differences in the multi-element signatures of the otolith core among sampling sites for all cohorts (2002, 2003, 2006 and 2007), indicating that the technique has considerable potential for use in future assessments of population connectivity and nursery areas of G. barbus. Via quadratic discriminant function analysis, fish were classified to natal nursery areas with 80–100% cross-validation classification accuracies. These results suggested that a high level of spatial segregation exists in adult catfish life and homing behaviour could not be ruled out on the basis of our data.