Trawl Collections Research Articles

Feeding habits, daily ration and vertical migration of the cape horse mackerel off South Africa

Crustaceans, principally cope pods and euphausiids, were most frequently found in the stomachs of Cape horse mackerel Trachurus trachurus capensis collected during demersal research surveys (1992–1995) in summer on the west coast and in winter on the south coast of South Africa. Fish (mainly pelagic) were infrequent < 10%) in the diet of fish from both coasts. The feeding periodicity, rate of gut evacuation and vertical migration of horse mackerel were investigated from midwater and bottom trawl collections taken during five diel sampling periods between 1993 and 1995 at fixed positions on the South Coast. Horse mackerel feed only during the day, mostly in late afternoon prior to their ascent into midwater at around sunset. Based on the exponential rate of decline in stomach fullness throughout the night, the rate of gut evacuation by horse mackerel was estimated to be 0.22·h−1. Using the Elliott and Persson method, the daily ration was estimated as 3.8% of wet body mass. Horse mackerel appear to migrate vertically for reasons other than feeding, and selective advantages of this behaviour are discussed.

Demersal fish assemblages along the Pacific coast of Costa Rica: a quantitative and multivariate assessment based on the Victor Hensen Costa Rica expedition (1993/1994).

During two cruise legs with the RV Victor Hensen (December 1993, February 1994), the demersal fish assemblages of the Golfo de Nicoya (GN), Bahía Coronado-Sierpe Terraba (ST) and Golfo Dulce (GD) areas were assessed from nearshore (approximately 20 m) to shelf edge (approximately 200 m) waters. 44 Beam- and 29 otter trawl collections were made on an area of 2,119,405 m2, yielding a total of 242 species of fish. Despite the lower number of samples taken, more species were collected by the otter trawl (189 compared to 160), due to a wider area swept. As revealed by the species-area curve and a longnormal-curve constructed from the pooled (log) abundance data, the fish assemblage appeared as well sampled and a theoretical species richness (SR) of-306 was estimated for the whole area. Mean species number per collection and mean biomass per area were much lower in the GD-area (9.3 species, 0.36 g/m2) compared to the ST (15.4, 0.81 g/m2) and GN (17.3, 0.74 g/m2) areas, indicating a depauperate fish assemblage in the former. Lowest species numbers and biomass were found in the central deep part of GD with increasing values towards the sill area at the opening of the gulf and towards the shallow stations above the thermocline. Average biomass was an order of magnitude higher in the interior part of GN compared to the other areas with values up to 18.1 g/m2. Based on results of a multivariate analysis of the collections, the GN area can be divided into (1) an interior shallow area above the thermocline (< 50 m) characterized by scianids, sea carfishes, stingrays, flatfishes, sea robins, (2) an outer part (> 100 m) characterized by cods, scorpionfishes, gobies, cutlassfishes, serranids, anglerfishes and flatfishes and (3) a transition zone of the central and lateral parts with a mixed species assemblage with carangids, pufferfish, snappers, several flatfish species and the lizardfish as common elements. Characteristic for the deep basin of GD were small species of the genera Cynoscion and Porichthys. These occurred in low densities, suggesting a reduced carrying capacity of this deep basin for fish biomass in terms of food and oxygen. Species occurring at the shallow stations of GD are also found at a similar depth in the other areas, but many species are missing, namely ariids and many scianids found in the GN area. The species assemblage of the ST area resembles that of GN. Ariids, however, are missing here too. Biotic station parameters like species richness, biomass, abundance and production were not significantly correlated with abiotic parameters (temperature, oxygen, nutrients) suggesting that other habitat factors not evaluated in this study like habitat heterogeneity, distance to the open ocean, current regime and food availability probably are important factors for the structure of the fish assemblage.

Diel feeding periodicity, daily ration and vertical migration of juvenile Cape hake off the west coast of South Africa

Feeding periodicity, daily ration and vertical migration of juvenile Cape hake Merluccius capensis are investigated from midwater and bottom trawl collections taken during a 42‐h period between 29 February and 2 March 1992 at a fixed position off the west coast of South Africa. Feeding of 10‐20 cm hake intensified during the night when they ascended into subsurface layers to prey on recruits of anchovy Engraulis capensis. Larger hake remained close to the bottom, were partially cannibalistic and exhibited no diel feeding periodicity. M. capensis appear to migrate vertically and feed asynchronously in midwater, as individuals, and not as a population, returning to the bottom when satiated. Based upon the exponential rate of decline in stomach fullness throughout the day, the evacuation rate by hake &lt;20 cm was estimated as 0.054 h−1; 90% evacuation of anchovy prey required an estimated 43 h. Using the Elliott &amp; Persson and Eggers methods, the daily ration was estimated as 5.51 and 4.15% of wet body weight respectively. The effect of the foraging behaviour of M. capensis on the appropriateness of acoustic sampling for estimates of their abundance is discussed.

The south-western limit for the warm-water, mesopelagic ichthyofauna of the Indo-West Pacific: lanternfish (Myctophidae) as a case study

The south-western limit for the warm-water, mesopelagic ichthyofauna of the Indo-West Pacific was investigated using tropical and broadly tropical lanternfish (Myctophidae). Two distribution patterns for these species are currently recognized in the eastern South Atlantic. Extended Agulhas Pattern species are distributed as sexually mature specimens from south-west of the Cape of Good Hope to about 19°S; Agulhas Pattern species (juveniles and expatriate adults), have a more restricted distribution. It has been hypothesized that the Extended Agulhas Pattern originates via the system of rings and incursions, which are generated at and inshore of the Agulhas retroflection, and that the Agulhas Pattern arises from larval drift across the Agulhas Bank and subsequent entrainment in the shelf-edge jet. The two hypotheses were tested mainly on the basis of trawl collections of juveniles and adults in the region 17–45°S, 10–40°E, and on larval collections over the shelf and slope regions of the west coast of southern Africa and the western Agulhas Bank. The east-to-west passage of Indo-West Pacific warm-water, oceanic myctophids into the eastern South Atlantic takes place only between the 200 m isobath of the Agulhas Bank (to the north) and the Subtropical Convergence (to the south). The probability for larval drift across the Agulhas Bank appears to be low. Both patterns can be broadly correlated with the dynamics of the Agulhas Current. Differences may reflect seasonality in the penetration of Agulhas Current water into the region and in the reproductive cycles of western South Indian Ocean myctophids, as well as differences in the coherency and lifetime of the rings, filaments and intrusions.

The Fish Community of a Shallow Tropical Lagoon in Belize, Central America

Trawl collections indicate that the fish community of the Belize barrier reef lagoon is dominated numerically and in biomass by grunts (Haemulidae), especiallyHaemulon sciurus andHaemulon flavolineatum. Although the gear selected for small sizes, length frequency analysis indicated seasonality in recruitment of the dominant species of grunts. Apogonids and tetraodontiform fishes were also dominant components of the community. Most fishes collected were juveniles of species that occur as adults on the main reef, or were small species that are resident in the lagoon. Of three habitats sampled, the mangrove creek had the greatest relative abundance and biomass of fishes, followed by the seagrass bed and the sand-rubble zone. There were no significant seasonal differences in fish relative abundance or biomass. Community structure analysis indicated a uniqueness in the mangrove fish community. Diversity (H′) was high, and was due to high species richness and evenness of distribution of individuals among species. The Belize barrier reef lagoon serves as an important nursery habitat for juvenile fishes.

Deep-sea fish assemblages in the Catalan Sea (western Mediterranean) below a depth of 1000 m

The analysis of 48 bottom trawl collections from the Catalan Sea below a depth of 1000 m has allowed the identification of two distinct demersal fish assemblages, occurring on the middle and lower slope. The Middle Slope Assemblage (MSA) and Lower Slope Assemblage (LSA), restricted to the middle (1000–1425 m) and lower (1425–2250 m) slope, respectively, each consist of two groups with distinct structures. While one group is relatively homogeneous, the other can be considered as comprising a faunal transition. Each assemblage is dominated by species possessing very different characteristics. The preponderance of middle and large size fish with high energy requirements in the MSA is replaced, in the LSA, by smaller and more passive species with lower energy requirements. These differences are reflected in a series of ecological parameters such as abundance, biomass, mean fish weight, species richness and mean species richness. A pronounced decrease in the value of these parameters is generally seen with increasing depth, reflecting the increasingly oligotrophic conditions. Furthermore, the highly stable environmental conditions of the western Mediterranean (where water temperature and salinity rarely change below a depth of 150 m), suggest that the observed zonations may be determined by biological factors. It is possible to relate the observed faunistic changes with the vertical distribution of mesopelagic organisms. These organisms play a fundamental role in the feeding ecology of demersal fish species of the slope, either directly as prey or indirectly by enriching the sediments, and thus determining the distribution of sedimentivorous invertebrate species.

Northern pipefish, Syngnathus fuscus, occurrences over the Mid-Atlantic Bight continental shelf: evidence of seasonal migration

Data from several areas in the northern Mid-Atlantic Bight indicate northern pipefish, Syngnathus fuscus, undergo seasonal, inshore-offshore migrations. Resident in estuaries during spring through fall, they move into nearshore continental shelf waters off Cape Cod in late September–October and off Long Island and New Jersey in November. Return to estuaries occurs in March–April. Most (> 90%) continental shelf otter trawl collections in fall (September–November) were at water temperatures of 10–15°C. Most (> 80%) spring (March–May) collections occurred at water temperatures of 3–6°C. The majority of offshore collections were within 20 km of the coast and over 90% were in depths between 10 and 20 m. Length frequency data reveal both young-of-year and older fish migrate, possibly to avoid colder estuarine water temperatures in winter.

Inter-Annual Distributions of Larval and Pelagic Juvenile Cod (Gadus morhua) in Southwestern Nova Scotia determined with two Different Gear Types

Ichthyoplankton surveys conducted during 1979 on the Scotian Shelf have shown coincident egg and larval distributions for cod (Gadus morhua) and other related groundfish species. These data have been used by other investigators to support the larval retention hypothesis, in spite of three limitations: the exclusive use of a single type of small sampling gear, limited sampling landward of the 50-m isobath, and analysis of data collected in a single year. During May of 1985, 1986, and 1987 two gear types were used, from the shelf to coastal waters in southwestern Nova Scotia to assess the horizontal distributions of larval and pelagic juvenile cod. Tucker trawl collections made in each year revealed a cohort of cod [Formula: see text] that was not evident in the smaller gear, which effectively sampled cod larvae &lt; 10 mm. During 1985 and 1986, when both larvae and juveniles were abundant, their distributions coincided. The mixture of sizes of cod from 3–45 mm reduced the importance of using multiple gear types. The interannual location of young cod shifted markedly between the nearshore and offshore demonstrating that a single year of sampling effort is inadequate to assess their distribution. Nearshore sampling revealed high densities of young cod as much as three-fold greater than offshore. The inshore waters may serve as a nursery area for young cod originating from offshore spawning sites. Our results confirm the existence of two important sampling limitations of previous cod ichthyoplankton surveys that reduce their utility as empirical support for the retention hypothesis.

Gulf of Mexico hydrocarbon seep communities—I. Regional distribution of hydrocarbon seepage and associated fauna

A series of otter trawls demonstrate that communities based on chemosynthesis are broadly distributed across the northwestern Gulf of Mexico continental slope in hydrocarbon seep areas. Thirty-nine trawls were taken at 33 locations reported to exhibit transparent or chaotic seismic “wipe-out” zones. The sites, in water depths from 180 to 900 m, span an area from offshore the Mississippi River delta to the upper Texas continental slope. Endosymbiont-containing organisms or their remains (either tube worms, mussels and/or clams) were recovered at 21 sites on the northern Gulf of Mexico slope. Tube worms, clams and mussels known to be associated with symbionts were retreived at 18, 12 and 5 sites, respectively. Carbon isotope analysis of selected animal tissues confirmed the chemosynthetic association. Animals containing isotopically light chemosynthetic carbon were collected at 21 sites. Piston cores at each site were used to determine the presence of mature hydrocarbons. Nine of 30 piston cores were visibly oil-stained. Trawl collections at locations where visibly oil-stained cores were recovered contained at least one species of chemosynthetic-associated organism and generally represented the most abundant catches of endosymbiont-containing animals. The chemical environment (oil and gas seepage) necessary to support chemosynthetic-based ecosystems is widespread on the northern Gulf of Mexico continental slope.

An Ostracode Commensal of an Ophiuroid and Other New Species of Pontocypria (Podocopida: Cypridacea)

Pontocypria hendleri, new species, is a commensal of the ophiuroid, Ophioblenna antillensis Liitken, collected from a reef in Belize. Pontocypria calva, new species, and Pontocypria sp. B occur in trawl collections from the southwest Pacific and North Atlantic, respectively. Pontocypria helenae Maddocks, previously found on Antarctic asteroids, now has been collected apparently free-living at seven localities in the South Atlantic and South Pacific. The ostracode genus Pontocypria was established by Miiller (1894) for the freeliving, actively swimming, Mediterranean species P. spinosa, collected among calcareous algae and detritus of Posidonia. Maddocks (1968, 1979) reported three commensal species of Pontocypria: P. helenae on three species of Antarctic asteroids, P. humesi from a sponge in Madagascar, and P. sp. (hereafter called P. sp. A) on a spatangoid echinoid in the North Atlantic. The Challenger lectotype of P. meridionalis (Brady, 1880), collected near the Falkland Islands, also belongs to this genus (Maddocks, 1968). In 1985 Gordon Hendler discovered that one specimen of an ophiuroid collected in Belize was infested with an ostracode, Pontocypria hendleri, new species. Each of the ostracodes was clinging by one antennal hook to the external integument of the disk or an arm of the brittle star, in the same manner illustrated earlier for P. helenae (Maddocks, 1968, pl. 2, fig. 2). The skin of this brittle star, Ophioblenna antillensis Liitken, has abundant sieve-like spicules small enough to be ingested, but none of these spicules are visible in the gut of the ostracodes, nor is there other evidence of harm to the host. As in other species of Pontocypria, the mouthparts are weakly constructed and the gut contents unidentifiable. Maddocks (1968) suggested that these species might feed on the soft organic detritus trapped by mucus secretions of the host or even on the mucus itself. Dr. Hendler reported (letter of 9 March 1987) that "the slimy skin and other characteristics of Ophioblenna antillensis indicate that the species should be referred to the Ophiomyxidae rather than the Ophiacanthidae as heretofore presumed. Ostracods that require hosts with relatively thick, mucus-producing integument would more likely occur with ophiomyxids than with ophiuroids that have a relatively thin layer of tissue covering the skeletal plates." The deliberate nature of this association is supported by the inclusion of a young juvenile as well as adult ostracodes of both sexes. Because there is no evidence that this association is either harmful or beneficial to the host, it is here classified as commensal. Perhaps any mucus-secreting echinoderm can be infested, and we should hasten to search holothurians and crinoids to see whether they, too, harbor these ostracodes! So far, each new class of host echinoderm has yielded a different species of Pontocypria, suggesting some antiquity for this relationship. The eurybathyal, cosmopolitan distribution of this genus further indicates significant geologic age, although the weakly calcified valves are poor candidates for preservation and have not been recognized as fossils. Two additional new species of Pontocypria, either free-living or detached from their hosts, have turned up in some trawl samples and are described below.

AN OSTRACODE COMMENSAL OF AN OPHIUROID AND OTHER NEW SPECIES OF PONTOCYPRIA (PODOCOPIDA: CYPRIDACEA)

Pontocypria hendleri, new species, is a commensal of ophiuroid, Ophioblenna antillensis Liitken, collected from a reef in Belize. Pontocypria calva, new species, and Pontocypria sp. B occur in trawl collections from southwest Pacific and North Atlantic, respectively. Pontocypria helenae Maddocks, previously found on Antarctic asteroids, now has been collected apparently free-living at seven localities in South Atlantic and South Pacific. The ostracode genus Pontocypria was established by Miiller (1894) for freeliving, actively swimming, Mediterranean species P. spinosa, collected among calcareous algae and detritus of Posidonia. Maddocks (1968, 1979) reported three commensal species of Pontocypria: P. helenae on three species of Antarctic asteroids, P. humesi from a sponge in Madagascar, and P. sp. (hereafter called P. sp. A) on a spatangoid echinoid in North Atlantic. The Challenger lectotype of P. meridionalis (Brady, 1880), collected near Falkland Islands, also belongs to this genus (Maddocks, 1968). In 1985 Gordon Hendler discovered that one specimen of an ophiuroid collected in Belize was infested with an ostracode, Pontocypria hendleri, new species. Each of ostracodes was clinging by one antennal hook to external integument of disk or an arm of brittle star, in same manner illustrated earlier for P. helenae (Maddocks, 1968, pl. 2, fig. 2). The skin of this brittle star, Ophioblenna antillensis Liitken, has abundant sieve-like spicules small enough to be ingested, but none of these spicules are visible in gut of ostracodes, nor is there other evidence of harm to host. As in other species of Pontocypria, mouthparts are weakly constructed and gut contents unidentifiable. Maddocks (1968) suggested that these species might feed on soft organic detritus trapped by mucus secretions of host or even on mucus itself. Dr. Hendler reported (letter of 9 March 1987) that the slimy skin and other characteristics of Ophioblenna antillensis indicate that species should be referred to Ophiomyxidae rather than Ophiacanthidae as heretofore presumed. Ostracods that require hosts with relatively thick, mucus-producing integument would more likely occur with ophiomyxids than with ophiuroids that have a relatively thin layer of tissue covering skeletal plates. The deliberate nature of this association is supported by inclusion of a young juvenile as well as adult ostracodes of both sexes. Because there is no evidence that this association is either harmful or beneficial to host, it is here classified as commensal. Perhaps any mucus-secreting echinoderm can be infested, and we should hasten to search holothurians and crinoids to see whether they, too, harbor these ostracodes! So far, each new class of host echinoderm has yielded a different species of Pontocypria, suggesting some antiquity for this relationship. The eurybathyal, cosmopolitan distribution of this genus further indicates significant geologic age, although weakly calcified valves are poor candidates for preservation and have not been recognized as fossils. Two additional new species of Pontocypria, either free-living or detached from their hosts, have turned up in some trawl samples and are described below.

Seasonal Occurrence of Larval and Juvenile Fishes in a Virginia Atlantic Coast Estuary with Emphasis on Drums (Family Sciaenidae)

The seasonal occurrence and relative abundance of larval and juvenile fishes, particularly members of the family Sciaenidae, from a Virginia Atlantic coast estuary were determined from ichthyoplankton and otter trawl collections made from March 1979 to March 1980. The larvae of 19 species in 14 families were identified in the ichthyoplankton. Larvae of the engraulid, Anchoa mitchilli (bay anchovy), and the atherinid, Menidia menidia (Atlantic silverside), dominated the samples and made up 13 and 22%, respectively, of the 9,440 larvae collected. Peak occurrence of all larvae was from May to August. The juveniles of 28 species in 19 families were identified from otter trawl collections. Juvenile sciaenids numerically dominated the trawl collecions and made up 68% of the trawl catch. Juvenile density peaked during September through December.

NOTES ON THE DISTRIBUTION AND BIOLOGY OF GALATHEIDAE AND CHIROSTYLIDAE (DECAPODA: ANOMURA) FROM THE MIDDLE ATLANTIC BIGHT

ABSTRACT Twelve species of Galatheidae and one species of Chirostylidae numbering 6,928 individuals were retrieved from trawl collections made on the continental shelf, slope, and rise in the Middle Atlantic Bight. The most abundant species collected was Munida iris iris which constituted >90% of the total catch of galatheoidean anomurans. Three other species (Munidopsis rostrata, Munida valida, and Munida longipes) comprised > 1% of the total number of Galatheoidea. The bathymetric distribution of Munidopsis spp. was confined to depths >500 m, whereas all except two Munida spp. were collected from the continental shelf and upper slope. Munida spp. and Eumunida picta produced large numbers of small eggs, whereas eggs from Munidopsis spp. were large and few in number. Ovigerous females of all species examined, except Munida microphthalma and Eumunida picta, had larger carapace lengths than males and other females. For most species, there was little evidence of reproductive seasonality since ovigerous females were collected throughout the year; however, ovigerous females of Munida longipes, Munidopsis bairdii, and Eumunida picta were collected only in fall or winter. Parasites of Galatheoidea were mainly bopyrid isopods and rhizocephalan barnacles. The incidence of parasitism was low for all species examined.

Abundance and Distribution of Juvenile Alosa Species off Southern New Jersey

Blueback herring (Alosa aestivalis) comprised 79%, alewife (A. pseudoharengus) 16%, and American shad (A. sapidissima) 4% of the juvenile Alosa taken in 221 bottom trawl collections made during December-April from 1972 to 1975 in coastal, southern New Jersey waters. Most of these fishes were less than 100–120 mm FL. All three species were most numerous in March. Coastal waters out to at least 8 km offshore provide a continuum of estuarine conditions favorable for overwintering by these fishes.

Structural Components of Eelgrass (Zostera marina) Meadows in the Lower Chesapeake Bay: Decapod Crustacea

Otter trawl collections of eelgrass habitats in the lower Chesapeake Bay during 1976–1977 produced 14 species of decapod crustaceans. These collections were dominated by palaemonid shrimp (Palaemonetes spp.), blue crabs (Callinectes sapidus), and sand shrimp (Crangon septemspinosa), each of which exhibited unimodal seasonal abundance curves with large summer peaks. Decapod abundance was positively correlated with plant biomass throughout the year. Decapod densities on vegetated bottoms were greater than on unvegetated bottoms, and nighttime abundance on each bottom type was greater than corresponding daytime abundance. Total decapod abundances in Chesapeake Bay eelgrass meadows appear to be much greater than those reported in North Carolina eelgrass or Gulf of Mexico turtlegrass habitats.

Deep-Water Sipuncula from the Gulf of Gascogne

An intensive study of the benthos at six deep-water stations in the Gulf of Gascogne was undertaken by the Centre Océanologique de Bretagne, Brest (during 1972–4) (Laubier &amp; Sibuet, 1977, fig. 1). These stations were repeatedly sampled with a variety of gear during seven different ‘Biogas’ cruises, and over 1900 sipunculans belonging to 16 species including one new to science were collected. Table 1 lists these species and their abundance at the six stations. Specific station data on the samples can be obtained from the authors.The ubiquitous nature of sipunculans is well documented by this work. Of the 72 dredge hawls made, 86% contained sipunculans, while 80% of the 54 trawl collections yielded sipunculans. Sample CP 01 with 165 sipunculans belonging to five species was the richest collection. The efficiency of the collecting gear and richness of the fauna is indicated by the fact that 24% of the individual collections yielded four or five species while 12% yielded 6–9 species, compared with the usual 1–3 species often collected. At Sample DS 62 a single haul yielded nine out of the 12 species at Station 1.The following section contains brief comments on the species and their distribution. Full descriptions of these species and additional references can be found in Stephen &amp; Edmonds (1972) and Cutler (1973). The subgenera of Golfingta follow Cutler &amp; Murina (1977) and Cutler (1979).

Mesopelagic fishes of the Bering Sea and adjacent northern North Pacific Ocean

Fourteen midwater trawl collections to depths of 450 m to 1,400 m were taken at eleven stations in the Bering Sea and adjoining regions of the northern North Pacific by the R/V Hakuho Maru during the summer of 1975. A total of 29 kinds of fishes were identified. Mesopelagic fishes of the families Myctophidae, Gonostomatidae and Bathylagidae predominated in the catches, contributing 14 species (94%) of the fishes caught.

Distribution of bottom fishes in the Denmark Strait and Irminger Sea

Analyses of 27 bottom trawl collections from the Denmark Strait and Irminger Sea show that five faunal assemblages of fishes can be identified. There are separable on the basis of faunal composition, diversity, evenness, catch rate, and the combination of depth and temperature at which each occurred. One group is found at 2026- to 2058-m depth and temperatures of 1.3 to 3.4°C, a second at 763 to 1503m and 3.9 to 5.6°C, a third at 280 to 776 m and 1.4 to 7.4°C, a fourth at 493 to 1519 m and 0.1 to 3.0°C, and a fifth at 330 to 693 m and −0.7 to +0.5°C. The assemblages are quite like those described for fishes trawled on the Iceland-Faeroe Ridge in 1960. Cold-water assemblages and species are found along the path of the Norwegian Sea water that flows south on the bottom through the Denmark Strait and down across the continental slope to the west. The percentage of primary deep-water species in each assemblage increases evenly with depth, suggesting a gradual and continuing invasion of the deep sea in this region by phylogenetically younger secondary deep-water forms. The smooth transition from an essentially shallow-water fauna to an essentially deep-water one as seen in the demersal fishes contrasts with the more abrupt transition found in pelagic fishes. The meso- and bathypelagic forms, presumably more highly specialized and finely tuned to their environment, are more successful in resisting invasion and colonization from newer groups. In the demersal assemblages, there is a good correlation between the number of species present and the heterogeneity of the local environment as reflected in the temperature range over which each of the assemblages occurs.

Larvae and Pelagic Juveniles of Blackgill Rockfish, Sebastes melanostomus, Taken in Midwater Trawls off Southern California and Baja California

Examination of 217 midwater trawl samples from the coastal basins off southern California and Baja California revealed a recurring group of rockfish species. The late larvae and pelagic juveniles of the blackgill rockfish, Sebastes melanostomus, constituted 16% of the total number of rockfish specimens. The life-history stages of this species are described, with emphasis on the pelagic juvenile stage. Late stage larvae and pelagic juveniles develop a distinctive pattern of melanophore bands which, by disrupting the body outline, may help conceal the young during their midwater existence. Evidence from midwater trawl collections suggests that 30-mm pelagic juveniles migrate or are carried shoreward at a depth of ~ 200 m to the appropriate habitat for settling. The high relative abundance of blackgill rockfish pelagic juveniles in midwater trawl samples suggests that this species may represent a potential resource. Key words: blackgill rockfish, Sebastes melanostomus, larvae, pelagic juveniles, midwater trawls, developmental stages, melanophore patterns, life-history strategy, head-spine development

Comparative biology of four species of glyphocrangonid and crangonid shrimp from the continental slope of the middle Atlantic Bight

Distribution, reproduction, food, and parasites of glyphocrangonid (Glyphocrangon sculpta and Glyphocrangon longirostris) and crangonid (Sabinea hystrix and Metacrangon jacqueti agassizi) shrimp were studied from otter trawl collections on the continental slope of the middle Atlantic Bight. Glyphocrangon sculpta and G. longirostris were found at depths of 2068–2679 m and 1111–2427 m respectively; S. hystrix was found from 452 to 2100 m and M. j. agassizi occurred from 616 to 1430 m. Among all four species, ovigerous females were significantly larger and more numerous than males. Sex ratio patterns expressed as percent male for depth and size are discussed for these species. Reproduction of all species was asynchronous and year-round; ovigerous females were captured during every month. Ovarian growth was continuous, enabling multiple spawnings of small numbers of large eggs. Stomach contents consisted almost entirely of benthic organisms and sediment, but the majority of stomachs were empty. Epibranchial bopyrid isopods were found on G. sculpta, G. longirostris, and M. j. agassizi. Parasite incidence among the species was low but, when present, retarded gonad development in female hosts.