Estructura y dinámica poblacional del Pargo Blanco Umbrina Canosai (Sciaenidae, Pisces) del litoral de Rio Grande do Sul, Brasil

A study of the population structure, dynamics and fishing of the pargo blanco Umbrina canosai was carried out during almost five years in Rio Grande, Rio Grande do Sul, Brazil. The species represents over 27% of the total demersal landings in Rio Grande and yielded up to 18,726 metric tons in 1976. The fishery in southern Brazil is described and the landing statistics for Argentina, Uruguay and Brazil are presented and discussed. The sampling strategy for size frequency distributions in the landings is described and the representativity and presicion of the mean size estimates is discussed. Scales and otoliths were used for ageing. Annual periodicity in the ring and zone formation was demostrated. Aged fish ranged from 0 to 21 years. Growth in length and weigth was described. Females grew faster and slightly larger than males and on the average lived longer. No difference in lengh-weight relation between sexes was observed. Seasonal changes of growth and of stomach content proportions showed that growth and feeding intensity were higher during summer and autumn. Size, sex and age group distributions were studied by means of landing samplings and 3 cruises of the R/V Atlântico Sul. Mean size become increasingly smaller with depth. Fishes under age II largly concentrate at depth over 60 m and older fishes in shallower waters. Yearlings were found in early summer near the coastline. The proportion of females was higher during the spawning season in winter and spring, when the species is more abundant insouthern Brazil platform. Males proportion was higher in the same region in summer and autumn. U. canosai is a serial spawner, larger females start spawning in august and the smaller ones in october and november. Larger females finish spawning and start southward migration first. Smaller females and males remain longer off Rio Grande. Mean size at maturity was 214±5 mm for females a 184±4 mm for males. At age 3, 97,6% of males and 80,1% of females were sexually mature. Fecundity ranged from 44,6 thousand eggs at 187 mm to 1450,6 thousand eggs at 377 mm and correlated positively with size, age and condition factor. Discard of inmature undersized fishes aged between 0 and 2 years was estimated to be 40-50% of the total number caught by trawlers. Most discard occured during the fishing season in areas where fishable socks were present. Age at first capture (tc) is 1,5 years for the cod end mesh sizes in use. Mean age in the landings dropped from 5.5 years during the 1976 fishing season to 3.8 years during 1980 season. Over se same period fishes above 8 years dropped in landings from 11.5% to 3%. Catch per unit effort of a standard fishing boat fell from 5.3 ton/day in 1975 to 2.5 ton/day in 1981. Total mortality (Z) over the study period was estimated to be between 0.6 and 0.8. Small mesh sizes and high fishing preassure are causing growth overfishing and reduction in the reproductive potential of the population which might endanger future recruitments. "Dynamic pool" models showed that 90% maximum yield per recruit for tc=3 years could be obtained at F= 0,2 to 0,38, depending on the natural mortality assumed. Economic yield per recruit for the present fishing mortality (F= 0,5) could increase by 50% if fish under 3 years were allowed to escape. Without management the stock is likely to stabilize at low production levels. If most of the fishing continues to occur in southern Brazil, management should consider a minimum mesh size of 90-100 mm, a minimum legal size of 230 mm and the discoragment in increase of number of fishing boats. Seasonal or regional closures would be difficult to enforce and of doubtful results. If fishing intensity on the species in Uruguay and Argentina increase international management should be considered.Fil: Haimovici, Manuel. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina

Reproductive biology of winter-spring spawners of Illex argentinus (Cephalopoda: Ommastrephidae) off Southern Brazil

The reproduction and fecundity of winter-spring spawners of the shortfin squid Illex argentinus off southern Brazil (27°S-34°S) were studied in samples from bottom trawl surveys on the outer shelf and upper slope from 1986 to 1992. The mantle length-total weight relationships were for males: TW = 0.00002456 ML2.974 for females: TW = 0.00004265 ML 2.842 and pooled: TW = 0.00005376 ML 2.809. Males were heavier than females at the same ML. Fully mature squids were found from July to October. Mantle length and total weight of fully mature males ranged from 188 to 296 mm (mean 252.2 mm) and 195.5 to 611 g (mean 382.7 g) and for females from 225 to 356 mm (mean 307.4 mm) and 234 to 772 g (mean 558.4 g). Total weight was maximum at full maturity and decreased in the subsequent stages of both sexes. Mean weight and mean major axis length of ripe oocytes in the oviducts were 0.48 mg (sd= 0.10 mg) and 1.27 mm (sd= 0.08 mm), respectively. Total and oviduct mean fecundities, in thousands of oocytes larger than 0.4 mm, in ten fully mature females (294-336 mm ML) were 177.2 (93.0 to 294.3) and 118.4 (51.5 to 233.9), respectively. Spawning season in this region seems to be more protracted than in higher latitudes. Our results suggest that a northward migration could take place prior to spawning and that in winter and spring, southern Brazil may be a major spawning ground of Illex argentinus that contributes to the local and to the Uruguay and northeastern Argentina recruitment

Reproductive cycle of Loligo sanpaulensis Brakoniecki, 1984 (Cephalopoda; Loliginidae) in southern Brazil

Loligo sanpaulensis the most abundant coastal squid in southern Brazil. The reproduction of the species was studied from 2,340 specimens obtained in eight groundfish surveys from 198 1 to 1987 along the coast of southern Brazil (28"35' S to 34"40' S), at depths from 10 to 587 m. On the shelf,' ripe specimens and mated females were found in all seasons, being less frequent in autumn. Most squids caught on the slope during all seasons were immature. The high frequency of fully mature females, and the occurrence of spent males, egg masses and loliginid paralarvae suggested that the species spawns off Southern Braz il. Mature individuals were mostly smaller than 80 mm mantle length (ML) in summer and autumn. In winter and spring, two spawning groups, with 50 - 80 mm ML and larger than 100 mm ML, were detected at depths under and over 40 m respectively. Off southern Brazil , the species has a long spawning period, with peaks in summer and winter/spring. The squid migrates across and along the shelf, taking advantage of the Brazil and Malvinas currents system to reach suitable spawning and feeding grounds. It is hypothesized that summer spawners may find adequate feeding grounds in winter in the outer shelf while winter spawners may recruit in part to the southern range of the species in northern Argentina in spring, eventually returning northward to reproduce

Eledone gaucha, a new species of eledonid octopod (Cephalopoda: Octopodidae) from southern Brazil

A new species of Eledone is described from the southwestern Atlanlic at deptlis of 60 to 160m, off Rio Grande do Sul, Brazil. The characters that dislinguish this species trom the other species of the genus are presented, as well as a morphometric comparison with the sympatic Eledone massyae Voss, 1964

Edad y crecimiento del lenguado Paralichthys orbignyanus (Teleostei: Pleuronectiformes) en el sur de Brasil

The red flounder Paralichthys orbignyanus is a large pleuronectiform fish endemic in coastal waters, coastal lagoons and estuaries in the southwestern Atlantic. Although less abundant than other Paralichthys spp., its high price makes it a valuable resource for small-scale fishers that have been intensely fished in the last decades. To study its growth and lifespan in southern Brazil, we examined thin otolith sections collected for age determinations of both young-of-the-year (YOY) and older fishes. Opaque bands form mainly in spring and summer, coincident with the reproductive season. Larger and older males reached 601 mm and eight years, while females reached 985 mm and 11 years. The assumed daily microincrements counts ranged from 127 to 196 for YOY of 135 to 184 mm TL. The common weight-length equation for grouped sexes was TW♀♂=0.000015TL2.93 (mm, g). The von Bertalanffy growth equations were: TL♀=1076(1–e–0.15 (t+0.78)); TL♂=652(1–e–0.28 (t+0.48)); and TL♀♂=839(1–e–0.20 (t+0.67)). Therefore, P. orbignyanus is a fast-growing and relatively short-living species for which females attain larger length and older ages than males, characteristics that have to be taken into account for its stock assessment and management.El lenguado Paralichthys orbignyanus es un pez pleuronectiforme de gran tamaño, endémico de aguas costeras, lagunas costeras y estuarios del Atlántico sudoccidental. Aunque menos abundante que otros Paralichthys spp., su alto precio lo convierte en un recurso valioso para los pescadores artesanales que los han pescado intensamente en las últimas décadas. Para estudiar su crecimiento y edad en el sur de Brasil, examinamos secciones delgadas de otolitos para realizar determinaciones de edades tanto de juveniles menores a un año como de peces más viejos. Las bandas opacas se forman principalmente en primavera y verano, coincidiendo con la época reproductiva. Los machos más grandes y mayores alcanzaron los 601 mm y los ocho años de edad, mientras que las hembras alcanzaron los 985 mm y los 11 años. Los recuentos de microincrementos diarios asumidos oscilaron entre 127 y 196 para los juveniles de 135 a 184 mm TL. La ecuación peso-longitud para sexos agrupados fue TW♀♂=0.000015TL2.93 (mm, g). Las ecuaciones de crecimiento de von Bertalanffy fueron: TL♀=1076(1–e–0.15 (t+0.78)); TL♂=652(1–e–0,28 (t+0,48)); y TL♀♂=839(1–e–0.20 (t+0.67)). Por lo tanto, P. orbignyanus es una especie de crecimiento rápido y vida relativamente corta, cuyas hembras alcanzan mayor longitud y edad que los machos, características que deben tenerse en cuenta para la evaluación y gestión de su población

Cephalopod paralarvae around tropical seamounts and oceanic islands off the north-eastern coast of Brazil

Early life cephalopod stages were collected around tropical seamounts and oceanic islands off the north-eastern coast of Brazil. A total of 511 specimens was caught with oblique Bongo net hauls between 150 m depth and the surface during a joint Brazilian/German oceanographic expedition with the RV VICTOR HENSEN in January/February 1995. Mean density of cephalopods was low with 24 ind 1000 m−3. Fifteen families representing at least 21 genera, from which 11 species were identified. The findings revealed a typical tropical and oceanic cephalopod assemblage. The most abundant families were Enoploteuthidae (27.6%), Ommastrephidae (20.9%), Onychoteuthidae (11.2%), Cranchiidae (10.4%) and Octopodidae (9.2%). Less abundant families were Octopoteuthidae, Thysanoteuthidae, Cthenopterygidae, Lycoteuthidae, Mastigoteuthidae, Tremoctopodidae, Argonautidae, Chiroteuthidae and Bolitaenidae. Highest cephalopod densities occurred along the Fernando de Noronha Chain (34 ind 1000 m−3). Small-sized Enoploteuthidae and Onychoteuthidae dominated in that region. Around the North Brazilian Chain overall cephalopod density was 31 ind 1000 m−3 where again, Enoploteuthidae were most abundant, closely followed by Ommastrephidae. Cephalopod abundance was the lowest (13 ind 1000 m−3) around the St. Peter and St. Paul Archipelago. However, cephalopod diversity was highest in this region (17 genera) with Enoploteuthidae dominating, followed by Cranchiidae. Cephalopod mantle lengths (ML) ranged from 0.8 mm to 25 mm. The majority of specimens were small-sized with 65% below 3 mm ML, and 81% below 4 mm ML. All major genera and species are illustrated and their meso-scale distribution patterns are discussed. The results provide new information on the species composition and distribution patterns of early life cephalopods in tropical seas

The population dynamics of the red porgy Pagrus pagrus along southern Brazil, before its fishery collapse in the 1980s: a baseline study

The intense exploitation since 1972 of the formerly only slightly exploited protogynous hermaphroditic fish Pagrus pagrus (L.) in southern Brazil has led in less than a decade to the collapse of the fishery, with no recovery four decades later. In this study we analized the age structure, growth, reproduction and mortality of the species were studied based on samples collected from 1976 to 1985 to provide a baseline before the onset of overexploitation. Maximum estimated ages were 21 and 26 years based on scale and otolith readings, respectively. Mean total length (TL) at age did not differ between males and females, while hermaphrodites were smaller. The von Bertalanffy growth coefficients for all fish (immature, females, hermaphrodites and males) were L∞ = 447 mm, k = 0.204 and t0 = −1.134 yr. Change in growth was observed during the study period. Females were dominant at all sizes, hermaphrodites were only present up to intermediate sizes, and males, despite being infrequent at small sizes, made up over 40% among the larger specimen (TL > 400 mm). Spawning took place mainly in late spring and condition factors were lower after spawning. Natural mortality was estimated as M = 0.173 yr−1 based on the von Bertalanffy growth parameters. Total mortality (Z) and exploitation rate (E) estimated from catch curves of fully recruited red porgies aged five to ten years increased from 0.24 yr−1 and 28% before 1973 to 0.49 yr−1 and 63% in the following years. Two distinct scale and otolith patterns, one with well-marked annuli and another with faint or absent annuli, suggested that the red porgy stock off southern Brazil might not be homogeneous and may include subpopulations that do not fully mix

Molecular Phylogeny of the Genus Lolliguncula Steenstrup, 1881 Based on Nuclear and Mitochondrial DNA Sequences Indicates Genetic Isolation of Populations from North and South Atlantic, and the Possible Presence of Further Cryptic Species

Squid of the genus Lolliguncula Steenstrup, 1881 are small bodied, coastal species capable of tolerating low salinity. Lolliguncula sp. are found exclusively in the New World, although only one of the four recognized species (Lolliguncula brevis) occurs in the Atlantic Ocean. Preliminary morphological analyses suggest that Lolliguncula brevis populations in the North and South Atlantic may represent distinct species. The principal objective of the present study was to verify the phylogenetic relationships within the genus and test for the presence of possible cryptic species. Both gene and species tree topologies indicated that Lolliguncula brevis specimens from the North and South Atlantic represent distinct phylogenetic clades. In contrast with previous studies, L. panamensis was identified as the basal species of the genus. Our results provide important insights into the phylogenetic relationships among the Lolliguncula specimens analyzed, and confirm the genetic separation of Lolliguncula brevis populations of the North and South Atlantic at the level of sister species

Otolith atlas for marine fishes of the southwestern Atlantic occurring along southern Brazil (28° S-34° S)

Otoliths are acellular apposition structures composed of approximately 90% of calcium carbonate and other inorganic salts, which develop over a protein matrix located in the inner ear of bony fishes playing an essential role in the senses of balance and hearing. These structures grow throughout a fish’s lifetime. Owing to their species-specific shape, otoliths are an important tool for the identification of fish species in the diet of predators when collected from stomachs and, due to their low water content, are helpful for archaeological, paleontological and anthropological studies for its presence in fossilized remains. This atlas is aimed at the identification of abundant or frequent bony fishes otoliths in the diet of predators and in fossilized remains from the continental shelf and upper continental slope of southern Brazil between Santa Marta Grande cape (28° S) and Chuí (34° S) on the border with Uruguay. It includes the otolith description of 136 bony fishes species, including most of the abundant and frequent species in the region. Easy to use graphics are provided to infer fish size based on otolith measurements. Vouchers of different sizes of otolith of all species included in this atlas are deposited and available for consultation at the Demersal Fisheries Resources and Cephalopods Laboratory (IO-FURG)