Feeding habits of the bluemouth, Helicolenus dactylopterus dactylopterus (Delaroche, 1809) (Pisces: Sebastidae) in the Portuguese coast

In order to investigate the feeding habits of Helicolenus dactylopterus dactylopterus along the continental Portuguese coast, a total of 619 individuals were sampled of which 60% contained food in their stomach and 35% had more than one prey item. Among the 81 prey items that were identified in the stomachs, benthic and benthopelagic prey prevail on this species diet. Acantephyra sp, Pasiphaea sp, mysidacea, and teleostei n.i. were the prey with the higher percent index of relative importance (%IRI) value. Three length groups (5?C20?cm, 21?C27?cm, and 28?C48?cm) were defined through cluster analysis of the mean abundance of prey items. A permutational MANOVA detected significant differences in the diet and stomach fullness index for TLG, season, and maturation stage. Smaller fishes had a generalized diet, feeding mainly on mysidacea changing their diet above 20?cm TL, where a major consumption of natantia was found. The larger individuals, >28?cm TL, present a less generalized diet with pisces as dominant prey group. Seasonally, natantia and pisces were the principal prey groups during spring and winter, respectively, while mysidacea and other crustaceans were predominant during the rest of the year. Mysidacea were also the main prey group for immature individuals while natantia and pisces were the principal prey groups to the other maturity stages. The results of this study indicate that H. d. dactylopterus has a diverse diet focused on small crustaceans such as misyds and as specimens grow shrimps and fishes become more consumed, with larger specimens having a more specialized diet. The different nutritional needs during spawning season also seemed to influence the feeding habits of H. d. dactylopterus.     

Feeding habits of grey gurnard,Eutrigla gurnardus (L., 1758), along the Catalan coast (northwestern Mediterranean)

The stomach content of 589 specimens of Eutrigla gurnardus (collected at quarterly intervals) have been analyzed to determine diet according to fish size and season. The results show that crustaceans (% No = 93%, %Weight = 81%) are the basic food and that teleostean fishes are quite important in the adult diet. The importance of nycthemeral migrators decreases significantly as size increases, whilst the importance of benthic prey increases inversely. In every size, the feeding intensity is greater at midday than in the morning. Larger prey are eaten in winter than in summer although feeding intensity is lower in winter.     

Benthic ctenophores (Platyctenida: Coeloplanidae) in South Florida: predator–prey interactions

The primary goal of this study was to demonstrate, from field observations and laboratory experiments, some key trophic roles of benthic ctenophores as predators and prey in subtropical communities. We examined individuals of two benthic platyctenid species: Coeloplana waltoni, a minute epibiont on octocorals in exposed, open‐water settings; and Vallicula multiformis, an associate of calm‐water biofouling communities and floating Sargassum spp. Laboratory observations of individuals of both ctenophore species revealed frequent capture and ingestion of diverse zooplankton taxa, especially crustaceans. Laboratory predation trials demonstrated the capture of dolphinfish (Coryphaena hippurus) eggs and larvae by both ctenophore species. Dolphinfish eggs and larvae larger than individuals of C. waltoni were captured but not ingested during 2‐h trial periods. These prey items were sometimes purloined and ingested by polyps of the ctenophore's octocoral host. Ingestion of dolphinfish eggs and larvae by individuals of C. waltoni was observed, however, after longer periods of exposure to prey. In predation trials, dolphinfish eggs and larvae were both captured and ingested by larger individuals of the ctenophore species V. multiformis. Field and laboratory observations revealed diverse invertebrate and fish taxa that prey on both ctenophore species. In the laboratory, the mean daily per capita consumption of individuals of C. waltoni by a pomacanthid fish ranged 0.5–2.8 individuals, and ranged 2.6–3.6 individuals for predation by an ovulid mollusc. Field population densities of these predators ranged 0.1–0.7 individuals per m² for the pomacanthid, and 0.2–1.1 individuals per m² for the mollusc. Laboratory feeding observations demonstrated frequent consumption of individuals of V. multiformis by a sea anemone, and by three species of brachyuran crabs. Field observations revealed eight fishes that probably feed incidentally on individuals of V. multiformis. These findings add to the limited knowledge base of predator–prey dynamics in both C. waltoni and V. multiformis.     

Feeding ecology of the lesser weever, Echiichthys vipera (Cuvier, 1829), on the western coast of Portugal

The feeding ecology of the lesser weever, Echiichthys vipera, from the adjacent coastal areas of the Douro and Tagus estuaries (Portugal) was studied between October 2000 and July 2002. The stomach contents of 246 individuals were analysed and diet was characterized by the numerical, gravimetric, occurrence and vacuity indices. Variation of feeding habits with fish length (<95 and >95 mm) and geographical area was considered. Diet of the lesser weever comprised a large variety of prey (28 species), the most important of which were crustaceans (numerical index, NI = 93.5%; occurrence index, OI = 75.6%), namely Mysidacea (especially Schistomysis sp.), Amphipoda (mainly Gammarus subtypicus) and Isopoda (Idotea spp.), and also Teleostei (mostly larval stages that posted a gravimetric index, GI = 53.0%). Diet varied with fish length, with large individuals showing a larger diversity of prey items. Furthermore, specimens from Douro also showed a higher diversity of prey items than those from Tagus. More than 50% of the stomachs were empty, being the highest vacuity values relative to smaller fishes as well as to individuals from the Tagus estuary adjacent coastal area.     

Feeding habits of <Emphasis Type="Italic">Bathydraco marri</Emphasis> (Pisces,Notothenioidei, Bathydraconidae) from the Ross Sea,Antarctica

In comparison with other bathydraconids, all species of the genus Bathydraco are poorly known from an ecological perspective. The diet of juvenile Bathydraco marri Norman, 1938 was studied for the first time in specimens collected in the southwestern Ross Sea during summer 1998. Fish were collected in a single otter trawl catch at 330–340 m depth. The stomach content analysis showed that this species fed exclusively on crustaceans. Overall, 20 prey taxa were identified to genus or species level. Mysids, amphipods and copepods were the most important prey in decreasing order of importance. Other prey, such as Euphausia superba, isopods and tanaids were eaten occasionally and in very small amounts. A multivariate analysis was applied to feeding data to assess ontogenetic or sex-related changes in diet. No difference was detected between sexes, whereas diet of small and large fish differed in some degree. An ontogenetic shift from small and pelagic crustaceans such as copepods to benthic–benthopelagic prey such as amphipods and mysids was observed. Relating present results with published data on physiological characteristics of B. marri, it was possible to infer their feeding behaviour and mode of life. Like other bathydraconids, this species appeared to be an inactive and sluggish fish, which relied on more or less motile benthic or epibenthic prey adopting a “sit and wait” feeding strategy. On the other hand, smaller fish seem to be more active, feeding also on pelagic prey such as copepods that can be seasonally abundant, thus reducing the intraspecific competition for food.     

Selective predation by crevalle jack <Emphasis Type="Italic">Caranx caninus</Emphasis> on engraulid fishes in the SE Gulf of California,Mexico

Feeding habits determine many aspects of living organisms, where it lives, the time of day that it is active, energy flow, biomass consumed and intra- and interspecific interactions, it which provides information to make predictions about the effects of fisheries on predator-prey relationships. Accurate predictions require a thorough understanding of predator diets and prey selection. In this study, specimens of the crevalle jack Caranx caninus were obtained between October 2012 and October 2014 in the SE Gulf of California, Mexico, in order to determine its feeding habits and prey selection. A total of 238 specimens were obtained, of which 94 (39.5%) had stomachs containing food and 144 (60.5%) had empty stomachs. A total of 10 prey items were identified, corresponding to seven families that included fishes, crustaceans and cephalopods. According to the Index of Relative Importance (IRI) the most important prey were Anchoa spp. (IRI = 91.2%), Engraulis mordax (IRI = 1.8%), and fish from the Clupeidae family (IRI = 1.0%). The crevalle jack’s diet did not change with the season (warm or cold). The crevalle jack was considered a tertiary predator (trophic level = 4.3) that tends to feed on a reduced number of prey, characterizing it as a specialist and selective predator of engraulid fishes (Levin’s index, Bi = 0.08; E = 0.6).     

Feeding habits of alfonsino Beryx splendens

The diet of the alfonsino Beryx splendens was determined from examination of stomach contents of 287 specimens of 17 to 48 cm fork length (L_F) sampled by bottom trawl on the Chatham Rise to the east of New Zealand. Prey items were predominantly crustaceans and mesopelagic fishes. The most important prey species by mass was Sergestes spp. prawns, followed by the myctophid Lampanyctodes hectoris, and then Pasiphaea spp. prawns. Multivariate analyses indicated that small crustaceans (euphausiids and amphipods) were most important in the diet of smaller B. splendens (100–424 g, 17–26·5 cm), with larger prawn species and mesopelagic fishes most important for larger fish (425–2070 g, 27–46 cm). Moon phase and bottom temperature also explained some of the variability in diet, but the moon phase effect was difficult to explain, and the bottom temperature effect may have been confounded, to some extent, with L_F. The results indicated that B. splendens were moderately selective feeders that foraged primarily in the mesopelagic layers. The diet of New Zealand B. splendens is generally similar to those reported from other areas, i.e. dominated by mesopelagic crustaceans and fishes, and with a transition from small crustaceans to fishes with increasing predator size.     

Diet composition of the Persian sturgeon <Emphasis Type="Italic">Acipenser persicus</Emphasis> at the coast of the Guilan Province,Caspian Sea

Sturgeons are one of the most important and valuable species in the Caspian Sea. This investigation (2000–2002) was aimed at determining the feeding habits and the main and secondary prey organisms consumed by the Persian sturgeon (Acipenser persicus Borodin, 1897) living at depths less than 10 m in the Caspian Sea (Guilan Province). The food spectrum of immature A. persicus was comprised of benthic invertebrates of seven genera and fishes of three genera. The main prey items of immature A. persicus were polychaete worms and the secondary prey were crustaceans. The study of stomach contents showed that polychaetes were the most important component of the diet of immature A. persicus of the length class up to 25 cm.     

Food habits of fishes in the surf zone of a sandy beach at Sanrimatsubara, Fukuoka Prefecture, Japan

To clarify the feeding habits of fishes in surf zones, the gut contents of 19 fish species collected in the surf zone of a sandy beach at Sanrimatsubara, western Japan, were examined. Ontogenetic changes in food preference were recognized in seven species (Mugil cephalus cephalus, Lateolabrax latus, Sillago japonica, Paralichthys olivaceus, Paraplagusia japonica, Takifugu poecilonotus, and Takifugu niphobles). A cluster analysis based on dietary overlaps showed that the surf zone fish assemblage comprised six trophic groups (zooplankton, benthic and epiphytic crustacean, detritus, polychaete, fish, and insect feeders). Of these, the most abundant trophic group was zooplankton feeders, along with benthic and epiphytic crustacean feeders.     

Feeding patterns of the dominant benthic and demersal fish community in a temperate estuary

The diet and feeding relationships of the 12 most abundant benthic and demersal fish species of the Mondego Estuary, Portugal, were studied between June 2003 and May 2006. Fishes were caught during the night using a 2 m beam trawl. The stomach contents were analysed for prey identification, counting and weighing. According to prey importance in diets, three main feeding guilds were identified: (1) invertebrate feeders, (2) invertebrate and fish feeders and (3) plankton and invertebrate feeders. Besides these main feeding guilds, some fishes also presented fractions of algae and zooplankton in their stomach contents. The most abundant prey items were macroinvertebrates, with several polychaetes ( Nephtys spp., Capitellidae, Spionidae and Eunicidae), Corophium spp. and Crangon crangon among the dominant prey. Pomatoschistus spp. were the most preyed on fishes. Several fish species showed a tendency for a specialized diet, but almost all also showed some degree of opportunistic feeding by preying on other food resources. High diet overlap was found between some fish species, yet exploitative competition could not be concluded.     

Marine reserves indirectly affect fine‐scale habitat associations,but not overall densities,of small benthic fishes

Many large, fishery‐targeted predatory species have attained very high relative densities as a direct result of protection by no‐take marine reserves. Indirect effects, via interactions with targeted species, may also occur for species that are not themselves targeted by fishing. In some temperate rocky reef ecosystems, indirect effects have caused profound changes in community structure, notably the restoration of predator–urchin–macroalgae trophic cascades. Yet, indirect effects on small benthic reef fishes remain poorly understood, perhaps because of behavioral associations with complex, refuge‐providing habitats. Few, if any, studies have evaluated any potential effects of marine reserves on habitat associations in small benthic fishes. We surveyed densities of small benthic fishes, including some endemic species of triplefin (Tripterygiidae), along with fine‐scale habitat features in kelp forests on rocky reefs in and around multiple marine reserves in northern New Zealand over 3 years. Bayesian generalized linear mixed models were used to evaluate evidence for (1) main effects of marine reserve protection, (2) associations with habitat gradients, including complexity, and (3) differences in habitat associations inside versus outside reserves. No evidence of overall main effects of marine reserves on species richness or densities of fishes was found. Both richness and densities showed strong associations with gradients in habitat features, particularly habitat complexity. In addition, some species exhibited reserve‐by‐habitat interactions, having different associations with habitat gradients inside versus outside marine reserves. Two species (Ruanoho whero and Forsterygion flavonigrum) showed stronger positive associations with habitat complexity inside reserves. These results are consistent with the presence of a behavioral risk effect, whereby prey fishes are more strongly attracted to habitats that provide refuge from predation in areas where predators are more abundant. This work highlights the importance of habitat structure and the potential for fishing to affect behavioral interactions and the interspecific dynamic attributes of community structure beyond simple predator–prey consumption and archetypal trophic cascades.     

Community structure of fishes attracted to shallow water fish aggregation devices off South Carolina,U.S.A.

Synopsis Twenty-two fish aggregation devices were deployed in 14 m of water off South Carolina. Species composition and abundance were determined by diver visual census on eight occasions from May through November, 1985. A total of 21 families and 36 species of fishes was observed at 121 stations. Pelagic fishes dominated the fauna with a 99.3% relative abundance, and Decapterus punctatus accounted for 97.6% of the individuals. Caranx crysos, Diplectrum formosum, Decapterus punctatus, Centropristis striata and Monacanthus hispidus were the most frequent species. Total fish abundance, number of species and abundance of four of the six most common species were significantly affected by season. Hurricane activity may have caused a significant drop in pelagic fish abundance at the FADs in July. No significant correlations among species abundances were found after removal of season and FAD type effects. Spatial zonation and seasonal occurrence patterns suggest some competition among pelagic fishes. Several factors that regulate FAD faunal abundance and composition are hypothesized, including: juvenile fish availability, availability of shelter, availability of adequate food resources, interspecific and intraspecific competition, severe sea conditions, and sporadic intrusions of large predatory fishes. It is hypothesized that the abundances of benthic and pelagic FAD fishes are correlated and that there is a direct or indirect energetic link between shallow water pelagic and benthic fish assemblages near FADs.     

Feeding ecology of larval and juvenile black seabream (Acanthopagrus schlegeli) and Japanese seaperch (Lateolabrax japonicus) in Tolo Harbour, Hong Kong

Black seabream, Acanthopagrus schlegeli, and Japanese seaperch, Lateolabrax japonicus, are important commercial species in the coastal waters of western Pacific Ocean, including Japan, Korea and China. In Hong Kong, larvae and juveniles of these two species occur in bays and estuaries during late winter and spring. This study reports on the ontogenetic changes in food habits in larvae and juveniles of these species in an artificial rocky shore area. Copepods and cladocerans were the most numerous food items for black seabream. There was a shift to larger and benthic prey as the fishes grew. Japanese seaperch <2.1cm fed predominantly on copepods and cladocerans, while larger prey were added as fish size increased. Japanese seaperch >6.0cm were piscivorous. Maximum prey width increased with fish standard length and mouth gape width in both species. Overall, black seabream showed greater diet breadth than did Japanese seaperch. In black seabream, diet breadth increased with fish size. In Japanese seaperch, diet breadth increased with size for fishes <4.0cm, then decreased as the fishes became piscivorous. Prey selectivity in black seabream was determined using information on prey availability in plankton samples. In general, preference was stronger for cypris larvae, Penilia avirostris and decapod larvae than for copepods and podonids. In recent years, overfishing and environmental degradation have led to the decline of fish populations in Tolo Harbour. Absence of fishes with empty gut indicates that inner Tolo Harbour is still an important nursery area for these two commercial species.     

Parasite transfer from crustacean to fish hosts in the Lübeck Bight,SW Baltic Sea

Four helminth parasites out of 19 species found in the Lübeck Bight, Baltic Sea, were chosen for investigations on the transfer from invertebrate to small-sized fish hosts: larvae of the tapewormsSchistocephalus sp. andBothriocephalus sp. (Cestoda) living in planktonic copepods as primary hosts;Podocotyle atomon (Digenea) andHysterothylacium sp. (Nematoda) were found in benthic crustaceans, especiallyGammarus spp. These hosts were the prey of 3 gobiid fishes,Gobiusculus flavescens (feeding mainly on plankton),Pomatoschistus minutus (preferring benthos), andP. pictus (feeding more on plankton than benthos). Because the fishes selected smaller sizes of crustaceans, they ingested all stages of the copepods but only the smaller-sized groups of gammarids which were often less infested by parasites. In order to evaluate the probability for a fish to be parasitized by a helminth, an infestation potential index (IP) was calculated.Podocotyle atomon andHysterothylacium sp. revealed an IP which was far lower in gobies than expected when the prevalences of the previous hosts were taken into consideration. The IP of tapeworm larvae was mainly influenced by the feeding pressure of the gobiid predators, which might change with developmental stage and season. It is concluded that parasite transfer to the next host decreases when sizes of prey and predator differ only moderately. This mechanism can reduce the numbers of parasites transferred to less suitable or wrong hosts.     

Feeding interactions and diet of carnivorous fishes in the Shelikhov Bay of the Sea of Okhotsk

The food spectra, trophic statuses, and feeding interrelations of three most abundant benthic carnivorous fish species inhabiting the Shelikhov Bay—the Pacific cod Gadus macrocephalus, the great sculpin Myoxocephalus polyacanthocephalus, and the Okhotsk sculpin M. ochotensis—are considered based on materials collected during the complex survey of the RV Professor Kaganovsky of the TINRO-Center, in September 2004. It was found that these species were facultative predators with wide food spectra. The significance of prey objects in the diet of the Okhotsk sculpin was as follows: crustaceans, fish, and mollusks. Great sculpin and Pacific cod preyed mostly on fish, then on crustaceans, and mollusks. Pacific cod ate equal proportions of fish and decapods. All the species had age-related variability of diet. The potential competition of great sculpin and Okhotsk sculpin for food was mitigated by the difference in the depths of their ranges, as well as by morphological (body size) and behavioral peculiarities in the areas where their habitats overlapped, and in microecosystems. The most probable competition was among Pacific cod 30–60 cm long and Okhotsk sculpin 20–50 cm in length, as well as among cod and great sculpins of all sizes.     

Feeding habits of bearded seals (Erignathus barbatus) from the Svalbard area, Norway

The objective of the present study was to assess the feeding habits of bearded seals (Erignathus barbatus) from the Svalbard area, Norway. Stomach and/or intestine contents were collected from 47 individuals shot between May and September (1989–1996). Prey specimens were identified from whole specimens or hard items such as fish otoliths, crustacean exoskeletons, cephalopod beaks, polychaete jaws, gastropod operculae and mollusc shell remains. To show the dietary contribution of the different prey items found in the gastrointestinal tracts, the frequency of occurrence and the numerical frequency methods were used. Fifty-nine percent or more of the gastrointestinal tracts contained five or more prey organisms. The most frequent fish species recorded was polar cod (Boreogadus saida), which was found in 49% of the gastrointestinal tracts, followed by sculpins (Cottidae spp.) (44%), long rough dab (Hippoglossoides platessoides) (28%) and the stout eelblenny (Lumpenus medius) (18%). The most frequent crustaceans were the spider crab (Hyas araneus) (59%), Sabinea septemcarinatus (54%), Sclerocrangon boreas (46%) and Lebbeus polaris (18%). Of the molluscs, the whelk Buccinum spp. occurred in 18% of the gastrointestinal tracts. Other species such as cephalopods, polychaete worms, amphipods and echiuran worms occurred in small amounts. There were no significant differences in foraging behaviour between males and females. This study also shows that in the Svalbard area bearded seals are benthic feeders and utilise a wide variety of organisms. Accepted: 26 August 1998     

Temporal variations in the diet of pearly razorfish Xyrichtys novacula (Osteichthyes: Labridae)

The diet of pearly razorfish Xyrichtys novacula, caught monthly along the shores of the Island of Lampedusa, appeared to be mainly composed of crustaceans, followed by colonial ascidians, molluscs and polychaetes. Among prey, sand dwellers and phanerogam‐associated species were recorded. In winter months, the diet was characterized by a small number of prey items, dominated by colonial ascidians, while in spring and summer a wider prey array was recorded. Dietary indices show that X. novacula do not strictly exploit benthic prey but also pelagic organisms, such as copepods. This feeding behaviour reached its peak in March and October, when the abundance of primary consumers was at its highest after phytoplankton blooms. Furthermore, X. novacula caught prey organisms according to their availability and seasonal patterns during their life cycles, irrespective of fish size.     

Feeding ecology and prey preferences of a piscivorous fish in the Lagoa do Peixe National Park, a Biosphere Reserve in Southern Brazil

We investigated the diet, feeding strategy, size-related dietary shifts and prey preferences of South American Hoplias aff. malabaricus in an internationally recognized but poorly investigated Biosphere Reserve in southern Brazil. Fish were caught between April 2008 and March 2009 using a variety of fishing gear. The analysis of 113 individuals revealed a diet essentially composed of fish (16 species), particularly characid species (9). The diet became more diverse and contained larger fish prey with increasing predator size. Feeding strategy analysis revealed a clear specialization towards the consumption of fish. However, individuals did not prey upon particular prey species, instead opportunistically consuming many different fish species, which could be a strategy to avoid intraspecific competition. Characid species were the most important prey, followed by poecillids. A multi-gear sampling of the ichthyofauna revealed that these prey species were the most abundant (Characidae: 61.3%, Poeciliidae 18.8%) of the 14 fish families occurring at the study site, suggesting that the predator exploits the most abundant fish resources available rather than the rarer fish prey. These findings suggest that potential top-down controls exerted by H. aff. malabaricus in this system follow specific food web pathways that seem to be mediated by the abundance of prey resources.     

Feeding habits of young predatory fishes in marsh creeks situated along the salinity gradient of the Schelde estuary, Belgium and The Netherlands

Fish and macrobenthos were sampled in four different marshes along the salinity gradient of the Schelde estuary, Belgium/Netherlands, to investigate the importance of marsh creeks as foraging grounds for the dominant, larger fish species. The total density and biomass of all the main macrobenthic taxa (Corophium volutator, Nereis diversicolor, Oligochaeta, Macoma baltica and Heteromastus fliliformis) were measured. The feeding habits of the larger predatory fishes (Platichthys flesus, Dicentrarchus labrax) were investigated. Qualitative and quantitative stomach analyses included the calculation of different indices, showing the niche breadth (as diet diversity) and the niche overlap (as similarity between the predators diet) for this habitat. These analyses showed that the two most important benthic prey species for P. flesus were C. volutator and N. diversicolor. D. labrax preyed upon a wider range of species, including C. volutator, N. diversicolor, Crangon crangon, Carcinus maenas and Orchestia spp. The stomach diversity of D. labrax and P. flesus showed differences between the marshes although there was no consistent pattern in diet composition, reflecting the opportunistic nature of feeding by these large predators. The fullness indices of both flounder and sea bass did not differ significantly along the salinity gradient and the estimated minimum consumption by these predators did not indicate a top-down control of the macrobenthic community. The salt marsh creeks seem to provide excess food for the visiting fish species. The benthic prey was present in very high abundances, which may suggest that the typical nursery species such as C. crangon and C. maenas, and early juveniles of P. flesus, D. labrax and Pomatoschistus microps were not preyed upon significantly. This supports the hypothesis that salt marsh creeks provide good refuge areas for nursery species against predation by larger fish.     

Why do juvenile fourhorn sculpin, Triglopsis quadricornis, appear in the pelagic habitat at night?

Synopsis Challenging the generally accepted view of the fourhorn sculpin Triglopsis quadricornis as a cold-stenothermal and true benthic species, novel findings of juveniles in the pelagic habitat of Lake Vättern, Sweden, have been examined and critically evaluated. Young-of-the-year and small-sized, sexually mature individuals, ranging 27–45 and 82–110 mm in total length, were recorded in nocturnal trawl catches from pelagic midwater in August. The sculpin had fed extensively on both benthic and semi-pelagic crustaceans, including large cyclopoid copepods, Mysis relicta, Pallasea quadrispinosa, Monoporeia affinis, Gammaracanthus lacustris, and Saduria entomon. Based on an extensive literature review a series of ecological and evolutionary reasons for a pelagic behavior of this profundal coldwater fish is suggested. Nocturnal, semi-pelagic feeding, and consecutive, thermotactic, vertical migrations up in midwater as shown by Wurtsbaugh & Neverman (1988) in order to maximize energy intake after feeding, are possible adaptations of these juvenile sculpin for minimizing size-dependent mortality due to intra- and interspecific predation and competition from other deepwater fishes.