RCAAP Repository

Studies carried out in various localities of the Province of Concepción, Chile (36º40'S; 70º06'W) estabilished the existence of two principal patterns of zonation defined by the populations of Mastocarpus sp. (¿ ?), Tridaea laminarioides, Gelidium pussflum, Ulva lactuca and Perumytilus purpuratus which occupy the lower hydrolittoral. In submerged levels the populations of Gracilaria and Macrocystis. form growths of moderate dimensions and in shallow waters, Iridaea ciliata, Gymnogongrus furcellatus and Gigartina chamissoii in scatterd patches.

The purpose of the present investigation is to evaluate the importance of the contribution of polychaetqus annelids to the feeding habits of fishes, crustaceans and molluscs from an important fishing area to the northern coast of São Paulo. Many of the species of fishes caught by otter-trawl, along the first phase of the present work have shown a remarkable preference for the polychaetes, as food items. Among them Rhinobatos horkelli, Orthopristis ruber. Cynoscion striatus, Menticirrhus americanus, Micropogon furnieri, Paralonchurus brasiliensis, Umbrina canosai, Etropus intermedius and Symphurus trewavasae are the most representative in this respect. The taxonomic analysis of the worms revealed the presence of 32 species, from which the more frequent was Nothria stigmatis, Pherusa laevis, Pherusa parmata, Piromis arenosus, Pectinaria laelia and Thelepus setosus.

30 echinoderm species (the crinoias excepted) have been recorded from the archibenthos off Central Chile. Samples were taken at 5 stations (from Los Vilos to Qutntero). 250-450 m depth range, every 15 days for one year. The concept of Region or Province, usually related to the intertital fauna from high latitudes are showed to be impractical using them with archibenthal echinoderms. The presence oj some species that had been registered as characteristic from the Antarctic Region and/or present in the Argentinian and Magellanic Province is related with the Antarctic Intermediate Water Mass, which is at the capture depth in the sampled area.

This study describes the scheme of the interspecific trophic relationships in the pelagic zone of the Argentine continental shelf in the coastal water region along the Province of Buenos Aires, in which the mackerel occupies the trophic levels corresponding to a plankton feeder of copepods of the zooplankton (third level), and to a small predator of the micronecton fish (fourth and fifth levels). The specific food spectrum is wide in the taxonomic composition and it consists of: Copepods, Amphipods, Euphausiids, Decapods (larval and postlarval stages), Chaetognats, small squids and fish, mainly anchovy in all development stages. The size of food species varies from 1 to 140 mm in length and the maximum diameter of the body from 0,8 to 20 mm; the diet is that of a small carnivorous fish tending to the euphagy characteristics of an opportunistic feeder. During the summer months some qualitative, Quantitative and chronological variations in the specific composition of the diet become erudent; these derive from the relative abundance of food species and the monthly sequence of the dominant modal classes in the shoals in this period, the anchovy is always frequent in the stomach contents of youngs and adults of the mackerel, such as larval and postlarval stages, young and adult fish. The capacity of food ingestion varies considerably between 5 and 22% with respect to the body weight of the consumer and the number of ingested specimens with the size of food species. The trophic equivalences calculated between the different food species also show qualitative and quantitative variations, mostly caloric and gravimetric in relation with the anchovy taken as basic food standard; therefore the adults of this species are considered as having the greatest utilitary value for the feeding of the mackerel during the period from October to April. The trophic habitat of the mackerel is included in the spawning and growing area of the anchovy, that at the same time is characterized by a high productivity of calanoid copepods, common food for both species. The food chain of the mackerel belongs to the intermediate type, between chains of simple disposition and food webs, and the main food is represented by two different successive links, one of the zooplankton crustaceans and other of anchovies. Generally, the intake of food is made by two different mechanisms: by filtration of elements of zooplankton (copepods) and by pursuing and capturing small preys (sergestids, chaetognats, squids, anchovies). From this point of view, the mackerel shows a high trophic adaptation characterized by the alternation and transitory change of trophic level and ecological niche, and by the morphological structure of some parts of the digestive system with regard to feedint habits. This last characteristic is also verified by the determination and statistical analysis of certain morphometric relations, mainly the buccal, mandibular intestinal and coelomatic quotiens.

From monthly zooplankton samples collected during October 1976 to October 1977, the seasonal variation of zooplankton standing crop and its relation to the number offish larvae from Bay of Concepción has been established. The zooplankton standing crop varied between 58 ml/m² in August and 430 ml/m² in January. The number offish larvae in the same sample ranged from 30 larvae /m² in January to 1045 larvae/m² in March. An inverse relationship between the zooplankton standing crop and the number of fish larvae it was checked and this relation is discussed according to the bibliographic antecedents.

The hydrographical conditions founded in Port Foster (Deception Island) and Chile Bay (Greenwich Island) both belong to the South Shetlands Islands group, Antarctic Peninsula, has been described. This survey has been carried out from the Chilean Navy Oceanographic vessel "YELCHO" in January 1978. An stratification in the area closed with the Antarctic surface waters has been observed. The temperature ranged between -1,60 º C to 1,30º C in Port Foster and 0,46ºC to 1,70ºC in Chile Bay; the salinity ranged between 33.80 ‰ to 34,24‰ in Port Foster and 33,61‰ to 34 ‰ in Chile Bay; the dissolved oxygen varied between 3,47 to 7,02 ml O2/l in both area. The characteristic density (Sigma t) of Antarctic Surface waters in the area, i.e., 26,92 and 27,58 has been observed.

Based on the information obtained from the Gulf of Fos, France, we propose herewith a generalized model to characterize the physical, chemical and biological parameters and their interrelationship in the eutrophic coastal system. This system is characterized by having high concentration of suspended materials, especially the mineral fraction (C/N >; 30). Nutrients concentrations are very high, except in diluted basins. The N-NO3/P-P04 ratio is usually low, due to the preferential assimilation of nitrates and the presence of polyphosphates from sewage waters. The concentrations of phaeopigments are always high (more than 50%), due to the mortalities of freshwater originated phytoplankton, the resuspension of dead vegetal materials, and the grazing of zooplankton. We noted in diluted water of eutrophic system the biomass is high, but the diversity is relatived low, among adapted cells with low " energetic charge". Whereas in oceanic water, the biomass is less, the diversity and energetic charge are increasing. This may indicate that phytoplankton communities have to make an effort to grow and duplicate. In comparing zooplankton populations from eutrophic to oligotrophic waters, biochemical diferentiations were observed for a same species, which may due to the difference in salinities and the presence of chemical pollutants.

This research has been done on the basis of samples obtained at depths between 21 and 63m by trawling in Golfo Triste. The stomach content of 153 specimens of Tethyaster vestitus and 981 specimens of Astiopecten riensis were analyzed. A.riensis seems to be an important element within the trophic structure of the community under study, constituting the second and third level of consumers. T.verstitus is, within the above-mentioned community one of the rare constitiuents of the 4th level consumers despite the fact that it takes part in the 3rd level as well.

Samples cited in the papers of Björnberg (1963, 1965) and some taken recently off Santos, Rio de Janeiro and Cabo Frio (Brazil) were restudied. The distribution of the several species of the genus Paracalanus (carassirostris, nanus, quasimodo, parvus s. str., indicus, aculeatus), of the genus Clausocalanus (furcatus, mastigophorus, pergens, ingens, paululus, parapergens and arcuicornis) were surveyed in Brazilian waters. Two new species Paracalanus campaneri and Delius sewelli were described. Two Ctenocalanus were found in Brazilian waters not corresponding to the description of Ctenocalanus citer. The distribution of these especies was compared off South America.

Growth discontinuity in molluscs result in the formation of rings on their shells. Two kind of rings may be formed: disturbance and growth rings. Growth rings can be used to determine the age of molluscs with long life span. For this, it is necessary to know how many growth rings are formed per year. It has been demonstrated experimentally, using marked specimens, that F. crassa forms two growth rings per year at Huayquique, Northern Chile. They are formed during winter and summer. Disturbance ring formation has also been observed as a result of sawing marks on their shells. A growth curve for this species is proposed on the basis of Watford's line.

A circalitoral muddy bottom community is studied off Punta del Este, Uruguay. From this study a relevant fact is observed: the coexistence between deposit-feeders and suspension-feeders. It has long been thought that they are excludent trophic groups. The coexistence may be explained by the deposit stability favourished by a dense population of the tube-building polychaete Onuphis setosa.

A taxonomic revision of some diatom species of the genera Biddulphia Gray and Triceratium Ehrenberg is made. The species are: B. azorica Pavillard, B. schroederiana Schussnig, B. membranacea Cleve. T. formosum Brightwell f.formosum, T. formosum f. quadrangularis (Hustedt), T. formosum f. quinquelobulata (Hustedt), T. shadboltianum Greville, T. shadbottianum f. elongata (Grunow) Hustedt and T. pelagicum (Schroder) Sournia. These species have poor siliciflcation of the frustules, reduced valvar apendixes and spines or none; these features could be regarded as adaptations to pelagic life. Descriptions and microphotographies of the species were made. These Biddulphia spp were found to be very close and some morphometric differences in the relation apical axe/pervalvar axe were taken in order to identify them quickly. All forms were found to be more frequent in no rain season and in high salinity waters (36 ‰). For T. formosum f. quadrangularis (Hustedt) and T. formosum f. quinquelobulata (Hustedt) some explanations were made about its real infrasnecific position, so that T. quadrangulare Greville and T. quinquelobutarum Greville should be regarded as different species of that forms of T.formosum Brightwell. B. azorica Pavillard and B. schroederiana Schussnig are first reported for the Caribbean Sea area.

The marine worm Paraprionospio pinnata population of a mud-bottom station at a depth of 65 m off Conception Bay, Chile, has been studied over the period October 1976 to October 1977. The epscies were counted, divided into year groups and the biomass of each group estimated as ash-free dry weight. Production estimate has been made by compunting mortality and residual biomass. Two year-class were present. The biomass, averaged over the year, was 1886 mg/m² and the production 4529 mg/m²/year, giving a P: B ratio of 2,4:1.

Qualitative and quantitative aspects of the benthic algal populations on the coastal reefs of Paraíba, Brazil, are given together with the distribution of the species along a transect from the beach to the outer edge of the reefs. A discussion is presented concerning the economic potential of the species found in the area.

The results of a study on the feeding habits of L. olivacea and C. mydas agassizi from the Pacific coast, located at 19ºN and 105ºW, are presented. A preference for feeding on crustacea was observed on L. olivacea, proving to be essentially a carnivorous specie. In the case of C. m. agassizi a certain balance between algae and animal feeding was appreciated, beeing the plants in a greater volume and animals more diversified. Related to animal preying C m. agassizi bucal structure, seems to be adapted toward the retention of animals captured with algae. Apparently there is no competition for food between both species,, given that L. olivacea feeds on organisms from sandy bottoms, while C. m, agassizi feeds on arrecifal or rocky bottoms.

A female Blainville's beaked whale, Mesopiodon densirostris, 4.4m long was found stranded at 42km, South of Cassino, Rio Grande do Sul, Brazil. The triangular shape and dimensions of the pair of unerupted teeth (60 x 45 x 11 mm) in the lower jaw, together with the distance (180mm) from the alveoli to the hinder edge of the mandibular symphysis proved to be a good systematic character for females of this species. The vertebral formula is C 7 + D 10 + L 11 + Ca 15 (+2) =45. It presents 10 pairs of ribs, 6 being double headed. M. densirostris is the only species of Mesopiodon which seems normally to occur both north and south of the equator and also the onlv species of this genus to strand on oceanic island of tropical and warm-temperature waters. The present record is the first for the Soutn West Atlantic waters.

The spring hydrographic conditions of Magellan flords region were described (i.e., Seno Almirantazgo, Bahía Inútil, Seno Otway and Golfo Xaultegua). The large differences in the water body observed among the fjords were related to the distance between the fjords to the shore and the influence of the coastal waters. Furthemore a seasonal variations analysis with spring and fall data has been carried out. The result shows that the most important parameter in the seasonal fluctuations of the water body was temperature.

The static biossays were performed to determine lethal concentration (LC50) values of four heavy metals (Cd++, Cr+++. Cu++. and Zn++) of spotted brown shrimp (Penaeus brasiliensis) The test animals were collected from the Laguna of Restinga, Nueva Esparto, and were acclimated in the laboratory condition for 11-21 days. Temperature and salinity were 22 ºC and 36 ppt, respectively. The LC50 values (mg/l) determined by probability-logarithm transformation were as follows-cadmium: 38 (24 -h), 21 (48 -h), and 12 (60 -h);chromium:40 (48 -h), 23 (60 -h), 13 (86 -h), and 10 (96 -h); copper: 24 (48 -h), 19 (60 -h), 16 (72 -h), 14 (86 -h), and 10 (144 -h); and zinc: 69 (24 -h), 25 (36 -h), 15 (48 -h) and 8 (60 -h). The LC50 values of 48 -h and 60 -h indicate that the most toxic heavy metals to P. brasiliensis in order are zinc, cadmium, copper, and chromium.

The critical thermal maximum (CTM) and the first equilibrium loss (FEL) of six tropical marine fishes were determined. CTM were Mugil curema (41.4º C), Genres sp. (39.2ºC), Orthopristis ruber (38.7ºC), Archosargus rhomboidalis (39.39ºC), Gobioides sp. (38.6ºC).and Chilomycterus sp (39.3ºC). FEL's were Mugil curema (40.7ºC), Gerres sp. (38.5ºC), Orthopristis ruber (37.2ºC), Gobioides sp. (36.0ºC), and Chilomycterus sp. (38.3ºC). The mean difference between CTM and FEL ranged from 0.93 to 2.66ºC and was significantly different.

The present paper deals with the results obtained on the basis of studies on the feeding and growth of juveniles of the croaker, Micropogon opercularis in experimental conditions. The following, more important results, were obtained: 1. - The values of the daily food requirement for the juveniles of 79-126 mm in total length and of 4.1-22 g in weight, at the beginning of the experiments, oscillated between 1,29 and 6,88%, with the average of 3,58 %. 2. -The efficiency of conversion of food is rather high and was calculated; for "normal" specimens as 19,45 % in average. 3. -Very big individual differences were observed in the growth of the juveniles. In the case of the total lengths, the rate of annual growth oscillated between 15,2 and 114,2% and. in the case of the weights, between 23,5 and 1114.5%. 4. -It was observed that in the scales of the juveniles under experiments the first annulus is not formed or is formed not always in a regular way.