Carácter de desove y fecundidad de la merluza argentina, Merluccius merluccius hubbsi, del sector bonaerense

The present paper deals with the spawning characteristics and the fecundity of the Argentine hake, Merluccius hubbsi from the zone in front of the Buenos Aires Province. More than 500 ovaries were studied and 168 of them were considerd in the statistical calculations.

Alimentación de la merluza en la región del talud continental argentino, época invernal (Merlucciidae, Merluccius merluccius hubbsi)

In the present paper the first results on the food and feeding habityas of hake in the region of the Argentinean continental slope are given. The data were obtained from the hake sampling made on board of the German research ship "Walther Herwig" during his first fishing exploratory trip in the Southwest Atlantic and from the investigation on the collected hake's stomachs.

Can a change in the spawning pattern of Argentine hake (Merluccius hubbsi) affect its recruitment?

Argentine hake (Merluccius hubbsi) inhabit waters of the Southwest Atlantic Ocean between 22° and 55°S, at depths ranging from 50 to 500 m (Cousseau and Perrota, 1998). This species has historically been among the more abundant fish resources in the Argentine Sea, where its biomass has ranged between one and two million metric tons annually since 1986 (Aubone et al., 2000). In this area, there are two identified fishing stocks, limited by the 41°S parallel. The southern group (Patagonian stock) is the more important with an abundance of about 85% of the total biomass estimated for this species in 1999 (Aubone et al., 2000). During the late 1990s, the spawning biomass of both stocks and their recruitment indices declined drastically, both of which were attributed to an increase in exploitation (Aubone et al., 2000).

Maternal effects on fecundity and egg quality of the Patagonian stock of Argentine Hake (Merluccius hubbsi)

The influences of age, size, and condition of spawning females on fecundity and oocyte quality were analyzed for the Patagonian stock of Argentine Hake (Merluccius hubbsi). Samples of mature females were collected in the spawning area as part of 2 research surveys conducted in January 2010 and 2011, during the peak of the reproductive season. Batch fecundity (BF) ranged between 40,500 (29 cm total length [TL]) and 2,550,000 (95 cm TL) hydrated oocytes, and was positively correlated with TL, gutted weight, age, hepatosomatic index (HSI), and the relative condition factor (Kn). Relative fecundity ranged between 85 and 1040 hydrated oocytes g–1 and showed significant positive relationships with gutted weight, HSI, and Kn; however, coefficients of determination were low for all regressions. Dry weights of samples of 100 hydrated oocytes ranged between 1.8 and 3.95 mg and were positively correlated with all variables analyzed, including batch and relative fecundity. Multiple regression models created with data of the morphophysiological characteristics of females supported maternal influences on fecundity and egg weights. Within the studied size range (29–95 cm TL), larger individuals had better somatic and egg condition, mainly revealed by higher HSI and hydrated oocytes with larger oil droplets (275.71μm [standard error 1.49]). These results were associated with the higher feeding activity of larger females during the spawning season in comparison with the feeding activity of young individuals (<5 years old); the better nutritional state of larger females, assumed to result from more feeding, was conducive to greater production of high-quality eggs.

La reproducción de la merluza en el Mar Argentino (Merlucciidae, Meluccius merluccius hubbsi) : 1. Descripción histológica del ciclo del ovario de merluza

The present paper deals on the histological description of the hake ovary made on the basis of gonad observations of 394 females during the period April 1966 March 1967. The material was obtained from weekly sampling of commercial catches carried out at the Institute of Marine Biology (Prov. Buenos Aires, Argentina). The anatomical and histological description of the standard ovary and the adopted terminology are given. The maturation process is divided into five periods, from ovocyte formation to yolked ovocyte formation, with its histological description. Ovary changes are analyzed on detail. The following conclusions were outlined: 1. Analysis demonstrated that although some specimens were totally spawned others, at the end of the spawning period, retaining a great number of ovocytes in different maturity stages. Therefore, postspawners have been classified as follows: Postspawned II : This stages is characterized by the empty ovarian structure, with ovocytes in stage II, which will remain in the resting phase untill next spawning season. Postspawned III and IV: Their main characteristics are: tissue destruction, bloody residuals and remaining ovocytes in stage III and IV, respectively. 2. Some transformations were found in ovaries of postspawned III and IV. They are classified as follows, according to its origin and structure: Developed from follicular cell membrane – a) Glandular formations, b) Epiteloid formations - Originated from remaining ovocytes, c) Ovocyte disintegration, d) Ovocyte with follicular cell infiltration. 3. All those structures derived from postpawners III and IV have a temporary character and will be reabsorbed. Their presence delay the recuperation of the organ and its reproductive functions. Consequently, the possibility of those structures acting as control mechanisms is suggested. 4. Transformations pointed out in paragraph Nº 2 prevent the possibility of consecutive spawning originated from the remaining ovocytes (II and IV). 5. No structures originated from postspawners III and IV were found during summer season. 6. Reproductive cycle of hake has been described monthly. It was observed that maturing ovaries predominate in summer (November-December).

La reproducción de la merluza en el Mar Argentino (Merlucciidae, Meluccius merluccius hubbsi) : 2. La reproducción de la merluza y su relación con otros aspectos biológicos de la especie

The paper deals with the spawning cycle of the hake, Merluccius merluccius hubbsi in the fishing area of the Argentine fleet, SW Atlantic (35°- 46° L. S.: 53°- 63° L.W.; 30-160 fathoms depth). It was made on the basis of the weekly sampling of the commercial catch in the period January 1965 - March 1968. The results have been compared with those of the exploratory surveys made by the United Nations Fisheries Development Program (República Argentina - FAO). The histological study, which was made with 741 specimens, was most intensive in females than in males. The results have been compared with the sexual stage determinations of both sexes in the total samples during the period before mentioned. The conclusions are: 1. The analysis of the ovocytes frequency distributions showed a period of resting or slow recuperation (April - August) with a mode of 120 ~k and one of rapid transformation (October - December) from 120 μ tíll 830 ~k. After December it appears again the mode of 120 ~k which indicated the reserve stock. 2. The maturity factor shows in both sexes a period of low values , 0,52 to 2% (April - September) and, another with higher values (October - March). In the first period the values are concentrated, while in the second one a large dispersion is observed produced by the rapidity of the growth process of the gonads. It is more evident between November and December. 3. The liver weight variations, compared with the degree of ingestion and the values of the maturity factor, in time, demonstrated that: a) after two periods of abundant ingestion (March - April and October- November) there are two increases of the liver index; b) the increase of the Iiver index has a direct relation to the maturity factor; c) at the end of the summer season, when the values of the maturity factor decrease, those of the liver index are still high. This demonstrates that the hake does not arrive exhausted at the end of the spawning season and that a rapid recuperation for a new spawning by part of the stock is possible. 4. Females predominate in the samples during most of the year. In the period October - December, when sexual activation occurs, as it is demonstrated by the high values of the maturity factor, proportions are nearly 1 :1, and males at times are more numerous than females. 5. The analisys of the advaneed maturity stages, in relation to total length shows that in the hake, Iike in other fishes, the largest ones mature first. This applies for both sexes. 6. The study of the maturity factor values and the sexual stages of the samples allows the recognition of two spawning periods, the main one in summer (October - March) and another in winter (June - July). 7. Part of the summer spawners, with a rapid recuperation, should be able to spawn again in winter. This indicates that the hake population, acording to our samples, has two different possibilities of spawning. 8. After analysis of the frequency percentages composition of mature specimens it is concluded that during the summer season, when hake is fished in shallow waters and in a wide area (38°– 43° L.S.) the fleet is fishing on the spawning stocks. Some winter spawners specimens have been found at 37°- 38° L.S. and in waters of more than 100 fathoms depth. 9. A new maturity scale of seven stages is proposed, instead of the one of six stages now in use. The new added stage corresponds to the postspawners during its resting period.

Spatio-temporal variations in the diet and stable isotope composition of the Argentine hake Merluccius hubbsi Marini, 1933 of the continental shelf of southeastern Brazil

The feeding ecology of Merluccius hubbsi was investigated in 2 regions of SE Brazil. The major food sources for the hakes were fish, crustaceans, and squid. In the upwelling system of Cabo Frio, the diet was very similar in the summers of 2001/2002 and spring 2002; fish were the most important prey followed by crustaceans. In Ubatuba, euphausiids were an important prey during the winter 2001 (100 m), while in the summer 2002, fish and amphipods predominated in the diet in the shallower site (40 m) and squid in the deeper site (100 m). The hakes showed temporal differences in stable isotope signatures in both regions, while C:N ratios varied only in Cabo Frio. delta(15)N and delta(13)C (bulk and corrected for lipid content) increased with fish length, which seems to be related to the increasing importance of fish and decreasing importance of euphausiids and amphipods in the diet of larger hakes. The mean trophic level of 3.7 for M. hubbsi was estimated using delta(15)N of bivalves as baseline and the fractionation of 3.4aEuro degrees between trophic levels.

Chartered Trawling on the Brazilian Slope

Commercial trawling on the Atlantic slope areas off Brazil intensified in the late 1990’s owing to the expansion of coastal trawling areas and the operations of a chartered foreign fleet. Between 2000 and 2003, 59 fishing trips conducted by 10 chartered trawlers were intensely monitored by observers and satellite vessel monitoring systems, totaling 9,069 tows and 30,085.2 trawling hours. Fishing operations occurred in northern, northeastern, southeastern, and southern sectors of the Brazilian coast in 60–1,173 m depths. Total retained and processed catch were 8,074.6 t and 6,479.8 t, respectively. Argentine hake, Merluccius hubbsi; and Argentine shortfin squid, Illex argentinus, were the primary species taken contributing to 41.1% and 28.6% of the overall catch, respectively. The silver John dory, Zenopsis conchifera; monkfish, Lophius gastrophysus; Brazilian codling, Urophycis mystacea; and the black grouper, Epinephelus nigritus, composed 23% of total processed catch, and the remaining 7.2% was composed of deep-sea shrimps (family Aristeidae) and other teleosts and elasmobranches. The occupation of slope areas included an early exploratory phase, followed by directed phases of the upper slope (300–500 m), aiming principally at the Argentine hake, and the lower slope (>700 m), targeting valuable concentrations of deep-sea aristeid shrimps. The role of chartering for slope trawling development was critically addressed. We conclude that chartered vessels were efficient explorers and were particularly important in areas not available to the technologically limited national fleet. Because the charters were market-oriented and had elevated profit demands, however, those vessels quickly turned from exploration to exploitation and competed with national trawlers in shallower areas and produced significant impacts on Brazil’s modest deep-sea resources.

Feeding habits of the atlantic spotted dolphin, Stenella frontalis, in southeastern Brazil

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Ecosystem fragmentation drives increased diet variation in an endemic livebearing fish of the Bahamas

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

The trophic role of the squid Loligo plei as a keystone species in the South Brazil Bight ecosystem

The issue of whether loliginid squid can influence the average structure of marine ecosystems in a keystone role, i.e. a strong effect with relatively low biomass, has not yet been examined. Here, the diet of Loligo plei in inner shelf waters of the South Brazil Bight was examined, as a first step, based on the stomach contents of 2200 squid hand-jigged in shallow water (, 30 m) and taken as bycatch of shrimp trawlers in deeper water (30-100 m). Diet varied by size, season, and fishing zone. Stomachs were not empty in similar to 12%, with more empty during winter. The range of mantle lengths of squid caught by jigging (101-356 mm) appeared to differ from the squid trawled (30-236 mm), and the diet also differed. Food categories recorded in deeper water did not include amphipods or polychaetes, but in both fishing areas, fish were the most common prey. The fish prey identified included Trachurus lathami, small pelagic species, trichiurids, and Merluccius hubbsi. Demersal species, such as Ctenosciaena gracilicirrhus, and flatfish were also present. An ecosystem network model is updated through which a mixed-trophic impact matrix and ""keystoneness"" indicators were calculated. Loligo plei represents an important link between pelagic and demersal energy pathways, with high indices of keystoneness.

FEEDING HABITS OF THE ATLANTIC SPOTTED DOLPHIN, Stenella frontalis, IN SOUTHEASTERN BRAZIL

This study presents new information on the feeding habits of the Atlantic spotted dolphins, Stenella frontalis, in the Western South Atlantic. Nine stomach contents of S. frontalis incidentally caught in fishing operations conducted by the gillnet fleet based on main harbour of Cananeia (25 degrees 00' S; 47 degrees 55'W), southeastern Brazil, were analyzed. These specimens were captured between 2005 and 2007. A total of 1 422 cephalopod beaks, 147 otoliths and three crustaceans were recovered from the stomach contents. The dolphins assessed preyed on at least eight different fish species of the families Trichiuridae, Carangidae, Sparidae, Merluccidae, Engraulidae, Sciaenidae, Congridae and Scombridae, five cephalopod species of the families Loliginidae, Sepiolidae, Tremoctopodidae and Thysanoteuthidae, and one shrimp species of the Penaeidae family. Based on the analysis of the Index of Relative Importance (IRI), the Atlantic cutlassfish, Trichiurus lepturus, was the most important fish species represented. Of the cephalopods, the squid Doryteuthis plei was by far the most representative species. Several items were reported for the first time as prey of the S. frontalis: Xiphopenaeus kroyeri, Tremoctopus violaceus, Semirossia tenera, Merluccius hubbsi, Pagrus pagrus and Paralonchurus brasiliensis. S. frontalis presented teuthophagous and ichthyofagous feeding habits, with apparent predominance of the first, and preyed mainly on pelagic and demersal items.

Feeding habits of the atlantic spotted dolphin, Stenella frontalis, in southeastern Brazil

This study presents new information on the feeding habits of the Atlantic spotted dolphins, Stenella frontalis, in the Western South Atlantic. Nine stomach contents of S. frontalis incidentally caught in fishing operations conducted by the gillnet fleet based on main harbour of Cananéia (25°00'S; 47°55'W), southeastern Brazil, were analyzed. These specimens were captured between 2005 and 2007. A total of 1 422 cephalopod beaks, 147 otoliths and three crustaceans were recovered from the stomach contents. The dolphins assessed preyed on at least eight different fish species of the families Trichiuridae, Carangidae, Sparidae, Merluccidae, Engraulidae, Sciaenidae, Congridae and Scombridae, five cephalopod species of the families Loliginidae, Sepiolidae, Tremoctopodidae and Thysanoteuthidae, and one shrimp species of the Penaeidae family. Based on the analysis of the Index of Relative Importance (IRI), the Atlantic cutlassfish, Trichiurus lepturus, was the most important fish species represented. Of the cephalopods, the squid Doryteuthis plei was by far the most representative species. Several items were reported for the first time as prey of the S. frontalis: Xiphopenaeus kroyeri, Tremoctopus violaceus, Semirossia tenera, Merluccius hubbsi, Pagrus pagrus and Paralonchurus brasiliensis. S. frontalis presented teuthophagous and ichthyofagous feeding habits, with apparent predominance of the first, and preyed mainly on pelagic and demersal items.

Estrategias de la anchoíta en un mar de tiburones : Las pymes conserveras marplatenses durante la valoración financiera (1975-2006)

Desde los años 70' Argentina se consolidó como un país pesquero, siendo la merluza hubbsi la principal especie capturada y exportada. Desde fines de la década de 1990 pequeñas y medianas empresas supieron conciliar extracción, manufactura y mercados explotando especies costeras, entre las cuales se destaca la anchoíta. El presente trabajo se centra en las estrategias de gestión, organización e innovación de Coomarpes e Indupesa, empresas que han subsistido en un mercado dominado por un poderoso oligopolio interno y por capitales foráneos que depredan el mar argentino y exportan productos con escaso agregado de valor hacia mercados europeos y asiáticos