Richard L. Haedrich

Parasitism and ecological relationships among deep-sea benthic fishes

We have studied the metazoan parasite fauna of 52 species of deep-living benthic fishes from depths of 53 to 5000m off the New York Bight (39–49°N; 70–72°W). 17144 parasites were recovered from 1712 fishes. The infestation rate was 80%, with an average of 12.5 worms per host. Percentage occurrence by group among all fishes was Monogenea 12.9%, Digenea 48%, Cestoda 22.1%, Nematoda 54.5%, Acanthocephala 3.8%, and Copepoda 4.5%. Differing composition of the parasite fauna in different fish species reflects differences in diet. Specialized feeders are rather distinct; generalized feeders, which predominate, show overlaps in parasite fauna. In individual species, changes in diet with growth are reflected in changes in the parasite fauna. Infestation rate is directly related to abundance of the free-living fauna; hence, fish from within the submarine canyon are more heavily infested than those living without. Although it contains fewer families and genera than shallow faunas, the deep-sea parasite fauna is not extremely unusual in terms of its abundance, diversity, or host specificity. At the greatest depths, parasite abundance and diversity dramatically decline.

Pelagic food of Coryphaenoides armatus, a deep benthic rattail

Abstract Stomach contents from 79 specimens of the macrourid Coryphaenoides armatus trawled at depths below 2600 m in Hudson Canyon fell into three major categories: benthic animals, pelagic animals, and items of terrestrial or neritic origin. Pelagic cephalopods and fishes, especially Chauliodus and Serrivomer spp., were important components of the diet, particularly of the larger fish, and it is suggested that C. armatus may move off the bottom into mid-depths to feed. The findings of vegetables, insect and bird remains, and strips of rubber and plastic in the stomachs indicate that this species is extremely generalized in its feeding habits. Its activities are important in transferring food energy from mid-depths over the deep-ocean floor, where rather large food items must be originally dispersed as finer particles.

Mesopelagic fishes and thermal fronts in the western Sargasso Sea

Analysis of 25 midwater trawl collections, disposed along the meridian 70°20′W from off Hispaniola to the Gulf Stream, showed a change in the mesopelagic fish fauna at about 27°N. The point of faunal change corresponded to a change in the temperature structure of the upper part of the water column, i.e., at a (the?) so-called “thermal front”, perhaps identical to the so-called “North Atlantic subtropical convergence”. Of 44 species occurring in four or more collections, 13 species were collected only to the north of the front and 1 species only to the south. By most criteria, north-of-the-front collections were larger than southern ones. This is in accord with the north-south difference in primary production noted by other workers which, in turn, seems atributable to the north-south difference in temperature structure. To the north the upper part of the water column is well stratified in summer only, while to the south it is well stratified at all seasons. Taken altogether, what is now known suggests that the thermal front logically divides the upper Sargasso Sea into northern and southern portions that differ in many ways.

Ceratoscopelus maderensis: Peculiar Sound-Scattering Layer Identified with This Myctophid Fish

A sound-scattering layer, composed of discrete hyperbolic echosequences and apparently restricted to the Slope Water region of the western North Atlantic, has been identified from the Deep Submergence Research Vehicle Alvin with schools of the meyctophid fish Ceratoscopelus maderensis. By diving into the layer and using Alvins echo-ranging sonar, we approached and visually identified the sound scatterers. The number of echo sequences observed with the surface echo-soutnder (1/23.76 x 105 cubic meters of water) checked roughly with the number of sonar targets observed from the submarine (1/7.45 x 105 cubic meters). The fish schools appeared to be 5 to 10 meters thick, 10 to 100 meters in diameter, and on centers 100 to 200 meters apart. Density within schools was estimated at 10 to 15 fish per cubic meter.

Pelagic capture of the epibenthic rattail Coryphaenoides rupestris

Abstract Forty-nine specimens of the macrourid fish Coryphaenoides rupestris were captured in the Denmark Strait in large pelagic nets fished from F.R.S. Walther Herwig at depths between 1000 and 2100 m, and 270–1440 m off the bottom. Such capture confirms suspected pelagic excursions, presumed since pelagic organisms are common prey, by this bottom-living animal. Other members of the genus also feed on pelagic organisms. Thus Coryphaenoides may be an important agent in the transfer of food energy from the pelagial to the deep sea floor.

Distribution of bottom fishes in the denmark strait and irminger sea

Abstract 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.

Genetic variability in deep-sea echinoderms

Abstract The electrophoretic mobility of enzymes in polyacrylamide gels was used a measure of genetic variability in deep-sea echinoderms. Both variable and monomorphic species were found. The levels of polymorphism and heterozygosity were similar to those of species living in shallow-water and terrestrial environments, evidence that these are unrelated to climatic stability. We propose that polymorphism is more probably related to the intensity of selection pressures and a reflection of biological fluctuations. A tendency toward a deficiency of heterozygotes from the number expected in Hardy-Weinberg equilibrium suggests that populations of the ophiuroid Ophiomusium lymani may be genetically isolated.

Diversity and overlap as measures of environmental quality

Abstract It is argued that indices of diversity (information function H ) and overlap (percentage similarity PS) can be used together to assess environmental quality. The method is tested using data on demersal fishes from nine Massachusetts estuaries and embayments. Annual diversity ranged from H (log e ) = 0.4–2.4, with low diversities in areas of apparent high pollution and higher diversities in areas of lesser pollution. Where annual diversity is low, little seasonal change is reflected in a high PS from season to season; where annual diversity is high, a relatively lower PS indicates a greater degree of change. For their calculation, both H and PS require the number of individuals in each species in a sample. This data should be considered important in the conduct of faunal surveys that contribute to an environmental impact statement.

Midwater fishes from a warm-core eddy

Abstract On a transect from Slope Water into the Northern Sargasso Sea during August 1967, one daytime midwater trawl was made to 210 metres in a warm-core eddy (200-m temp. 16·1°C) at 40°04′N 67°13′W. The fish catch in the eddy, 5 species at a rate of 0·5 cm 3 /hr, was relatively very poor, for comparable Slope Water trawls (200-m temp. 3 /hr and Northern Sargasso Sea trawls(200-m temp. > 18°C) took 11 species at a rate of 1·0 cm 3 /hr. Qualitatively, the eddy trawl was also distinctive, sharing but one species with the 5 most abundant species in comparable Slope Water collections and one with the 5 most abundant in the Northern Sargasso Sea.