Adaptive response of Peruvian Hake to overfishing

Compensatory mechanisms of the Peruvian hake population (Merluccius gayi peruanus) in response to heavy exploitation and changes in species interaction are discussed. Changes in the rate of cannibalism, diet composition, maximization of fecundity and behavioral adaptation are noted.

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.

Feeding habits of European hake (Merluccius merluccius) in the central Mediterranean Sea

European hake (Merluccius merluccius) is an important predator of deeper shelf-upper slope Mediterranean communities. It is a nectobenthic species distributed over a wide depth range (20−1000 m) throughout the Mediterranean Sea and the north east Atlantic region (Fisher et al., 1987). Notwithstanding the ecological and economic importance (Oliver and Massutí, 1995) of hake in the Mediterranean, many aspects of its biology (e.g., recruitment and reproduction), due to multiple spawning (Sarano, 1986) and the current state of exploitation, are poorly understood (Arneri and Morales-Nin, 2000).

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).

Pacific Hake, Merluccius productus, Autecology: A Timely Review

Pacific hake, Merluccius productus, the most abundant groundfish in the California Current Large Marine Ecosystem (CCLME), is a species of both commercial significance, supporting a large international fishery, and ecological importance, connecting other species as both predator and prey. Coastal Pacific hake migrations are characterized by movements between northern summer feeding areas and southern winter spawning areas, with variations in annual abundance, distribution, and the extent of these movements associated with varying climate-ocean conditions. In general, warm (cool) years with enhanced (reduced) stratification and poleward (equatorward) transport are often related to good (poor) recruitment, increased (decreased) northward distribution, and reduced (enhanced) growth. However, the classic periodic pattern of annual migration and distribution may no longer be fully representative. Based on recent advances in the understanding of climate-ocean variability off the U.S. west coast, we hypothesize that the annual movements of Pacific hake are more responsive to climate-ocean variability than previously thought, and further, that changes observed in Pacific hake distributions may reflect long-term changes in climate-ocean conditions in the CCLME. Therefore, an updated model of these relations is key to effective monitoring and management of this stock, as well as to devising scenarios of future change in the CCLME as a result of climate variations. The current state of knowledge of the relationship between the Pacific hake and its environment is reviewed, highlighting emerging ideas compared to those of the past, and priorities for future research are suggested.

Inhibition of Protease Activity in Muscle Extracts and Surimi from Pacific Whiting, Merluccius productus, and Arrowtooth Flounder, Atheresthes stomias

Muscle extracts of Pacific whiting, Merluccius productus, and arrowtooth flounder, Atheresthes stomias, were assayed for proteolytic activity using azocasein as a substrate. Pacific whiting extracts showed maximum activity at pH 5.0-5.2 and a temperature of 50°C, while arrowtooth flounder extracts had maximum activity at pH 5.5 and 55°C. Three sources of inhibitors (potatoes, egg white, beef plasma protein) were evaluated in vitro for inhibition of protease activity. All three were found to be effective inhibitors in crude muscle extracts. Further studies utilizing these inhibitors in surimi showed that potato was equivalent to both egg white and beef plasma protein in preserving the gel forming characteristics ofheated kamaboko in both species.

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.

A note on some parasites of Merluccius capensis (Pisces) and their zoogeographical significance

During the Southeastern Atlantic Expedition of the German fishery research vessel "Walther Herwig" in 1967 the main emphasis lay on selective fishing of the South African hake Merluccius capensis (von BRANDT 1967). Some of the fish were found to be infested by ecto-and endoparasites both of which were collected whenever possible. Large plerocercoids of Dibothriorhynchus grossum whose adult stage lives in the South Atlantic Ocean in Lamna cornubica (L.SZIDAT, personal communication) were quite common as were cysticercoids of a Tetrarhynchus sp., which had also been reported in Cynoscion striatus off the Argentinian coast (MACDONAGH 1927, cited in Szidat, personal communication). Brownish nematodes were infesting the ovaries of several fish, but could not be identified. The most common ectoparasite to be observed was the parasitic isopod Livoneca raynaudii (fam. Cymothoidae) whose early larval stages were also found.

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.

Distribution, Abundance, and Biological Characteristics of Groundfish off the Coast of Washington, Oregon, and California, 1977-1986

We compare results of bottom trawl surveys off Washington, Oregon, and California in 1977, 1980, 1983, and 1986 to discern trends in population abundance, distribution, and biology. Catch per unit of effort, area-swept biomass estimates, and age and length compositions for 12 commercially important west coast groundfishes are presented to illustrate trends over the lO-year period. We discuss the precision, accuracy, and statistical significance of observed trends in abundance estimates. The influence of water temperature on the distribution of groundfishes is also briefly examined. Abundance estimates of canary rockfish, Sebastes pinniger, and yellowtail rockfish, S. Jlavidus, declined during the study period; greater declines were observed in Pacific ocean perch, S. alutus, lingcod, Ophiodon elongatus, and arrowtooth flounder, Atheresthes stomias. Biomass estimates of Pacific hake, Merluccius productus, and English, rex, and Dover soles (Pleuronectes vetulus, Errex zachirus, and Microstomus pacificus) increased, while bocaccio, S. paucispinis, and chilipepper, S. goodei, were stable. Sablefish, Anoplopoma fimbria, biomass estimates increased markedly from 1977 to 1980 and declined moderately thereafter. Precision was lowest for rockfishes, lingcod, and sablefish; it was highest for flatfishes because they were uniformly distributed. The accuracy of survey estimates could be gauged only for yellowtail and canary rockfish and sablefish. All fishery-based analyses produced much larger estimates of abundance than bottom trawl surveys-indicative of the true catchability of survey trawls. Population trends from all analyses compared well except in canary rockfish, the species that presents the greatest challenge to obtaining reasonable precision and one that casts doubts on the usefulness of bottom trawl surveys for estimating its abundance. (PDF file contains 78 pages.)

Age determination methods for northwest Atlantic species

The successful application of techniques to enhance detection of age marks in biological specimens is of vital importance in fisheries research. This manual documents age determination techniques used by staff at the Woods Hole Laboratory, National Marine Fisheries Service. General information on procedures for preparing anatomical structures is described, together with criteria used to interpret growth patterns and assign ages. Annotated photographs of age structures are provided to illustrate criteria. Detailed procedures are given for the following species: Atlantic herring (Clupea harengus), haddock (Melanogrammus aeglefinus), Atlantic cod (Gadus morhua), pollock (Pollachius virens), silver hake (Merluccius bilinearis), red hake (Urophycis chuss), black sea bass (Centropristis striata), weakfish (Cynoscion regalis), Atlantic mackerel (Scomber scombrus), butterfish (Peprilus triacanthus), redfish (Sebastes fasciatus), summer flounder (Paralichthys dentatus), winter flounder (Pseudopleuronectes americanus), witch flounder (Glyptocephalus cynoglossus), American plaice (Hippoglossoides platessoides), yellowtail flounder (Limanda ferruginea), surf clam (Spisula solidissima), and ocean quahog (Arctica islandica). (PDF file contains 142 pages.)

Food habits and dietary variability of pelagic nekton off Oregon and Washington, 1979-1984

The food habits of 20 species of pelagic nekton were investigated from collections made with small-mesh purse seines from 1979-84 off Washington and Oregon. Four species (spiny dogfish, Squalus acanthias; soupfin shark, Galeorhinus zyopterus; blue shark, Prionace glauca; and cutthroat trout, Salmo clarki) were mainly piscivorous. Six species (coho salmon, Oncorhynchus kisutch; chinook salmon, O. tshawytscha; black rockfish, Sebastes melanops; yellowtail rockfish, S. f1avidus; sablefish, Anoplopoma fimbria; and jack mackerel, Trachurus symmetricus) consumed both nektonic and planktonic organisms. The remaining species (market squid, Loligo opalescens; American shad, Alosa sapidissima; Pacific herring, Clupea harengus pallasi; northern anchovy, Engraulis mordax; pink salmon, O. gorbuscha; surf smelt, Hypomesus pretiosus; Pacific hake, Merluccius productus; Pacific saury, Cololabis saira; Pacific mackerel, Scomber japonicus; and medusafish, Icichthys lockingtom) were primarily planktonic feeders. There were substantial interannual, seasonal, and geographic variations in the diets of several species due primarily to changes in prey availability. Juvenile salmonids were not commonly consumed by this assemblage of fishes (PDF file contains 36 pages.)