André Martins Vaz-dos-Santos

Length-weight relationships of the ichthyofauna associated with the Brazilian sardine, Sardinella brasiliensis, on the Southeastern Brazilian Bight (22°S-29°S) between 2008 and 2010

In this study, estimates of length-weight relationships are presented for twenty-four species caught in association with the Brazilian sardine, Sardinella brasiliensis, during four acoustics surveys carried out under the Program ECOSAR (Prospecting and evaluation of biomass of the stock of Brazilian sardine on the southeast coast by acoustic methods), which was to evaluate the biomass of species that were caught. The model parameters were estimated with the nonlinear iterative method of least squares. The value of the coefficient of determination (r2) and residual analysis were employed to verify the appropriateness of fit. The coefficient b values were tested with respect to isometry (β=3) using a tα1,0.05 test. The values of coefficient b ranged from 2.377 to 3.538. There is a tendency for positive allometry (b) in the sampled ichythyocenose.

Length-weight relationships of the ichthyofauna from a coastal subtropical system: a tool for biomass estimates and ecosystem modelling

Aiming to analyse the growth pattern, to allow biomass estimates and consequently to subsidize the ecosystem modelling, the length-weight relationships (LWR) of 39 fish species from the Araca Bay, a subtropical coastal area chosen as model for a holistic study comprising environmental, social and economic aspects have been estimated. The objective of this study was to provide LWR for the fishes from the area itself, accurately based on the life stages of fish populations present there. Particularly for Albula vulpes, Trachinotus carolinus, T. falcatus, Archosargus rhomboidalis and Kyphosus sectatrix these are the first records of LWR in Brazil.

Displacements of Anchoa tricolor (Spix & Agassiz, 1829) in a subtropical estuary revealed by the otolith microchemistry

This study aimed to describe the displacements of anchovy ( Anchoa tricolor ) in a subtropical estuary in South America, using the otolith microchemistry. We analyzed 198 specimens of A. tricolor in the Paranagua Estuarine Complex (Brazil) and data of salinity and rainfall. The biological and environmental data were grouped into sectors (internal, intermediate and external) and periods (early and late rainy and dry periods). The concentrations of Ca, Ba and Sr were determined using an ICP-OES. The Sr: Ca ratio indicated the existence of two groups of probably different origins that use the estuary at the same time but occupy different sectors of the estuary. In the other periods and sectors, we observed that part of the A. tricolor population used the estuary for feeding and growth, with an increase in the Sr: Ca ratio. The Ba: Ca ratio did not differ groups of use in the estuary, but rather, revealed low values suggesting that this species does not use freshwater environments. However, this ratio showed a high variation in the rainy period, indicating greater availability of barium in the estuarine regions affected by river discharge. Considering our results, it is possible to classify A. tricolor as an estuarine migrant species that uses estuaries for feeding and growth. Also, Sr: Ca and Ba: Ca ratios can be indicative of spatial and temporal displacement, respectively.

Environmental indicators in effluent assessment of rainbow trout (Oncorhynchus mykiss) reared in raceway system through phosphorus and nitrogen

The phosphorus and nitrogen discharge via effluent of intensive trout farming system was quantified through the use of environmental indicators. The nutrient loads, the mass balance, the estimated amount of nutrients in feed and the amount of nutrients converted in fish biomass were calculated based on the concentrations of phosphorus (P) and nitrogen (N) in the feed and in the water. Of the offered feed, 24.75 kg were available as P and 99.00 kg as N, of these, 9.32 kg P (38%) and 29.12 kg N (25%) were converted into fish biomass and 15.43 kg P (62%) and 69.88 kg N (75%) were exported via effluent. The loads and the mass balance show the excessive discharge of nutrients via effluent, corroborated by the feed conversion ratio (2.12:1) due to the low efficiency of feed utilization, therefore, it is proposed the use of this zootechnical parameter as environmental indicator. In addition, feed management practices are not adequate, highlighting the low frequency of feeding during the day, excessive amount and low quality of feed offered. These results demonstrate the need for adequate feed management and the need for careful monitoring of effluent.

Reproduction of the silver John dory Zenopsis conchifer (Actinopterygii: Zeiformes) based on virgin stock condition

This study describes the reproduction of the silver John dory, Zenopsis conchifer, based on data collected before its fishery exploitation in the southwestern Atlantic, Brazil, in the early 2000s. Biological material was collected through bottom-trawl surveys in 2001 and 2002 from depths of 100 to 600 m. A total of 1,056 individuals ranging from 57 to 504 mm Ls were analyzed. A sex ratio analysis showed that males were predominant among the shorter fishes ( 320 mm Ls). Between 240 mm and 319 mm Ls sex-ratio was 1:1. The silver John dory is a multiple spawner. Spawning is protracted and more intensive during August and November, when both females and males in spawning capable actively spawning and in regression/regeneration stages were predominant. In this period average values of gonadosomatic index were also higher. For both sexes, the first maturation occurs at 220 mm Ls and at 240 mm Ls all fish can be considered adult. The recruitment apparently takes place from February to May. The length-weight relationships fitted to all specimens and for both sexes yieldedb coefficients of ∼2.7. The virgin stock ofZ. conchifer here characterized, may serve a basis for future studies on the effects of fisheries on the reproduction of the species.