Diet and endogenous carbohydrases in the temperate marine herbivorous fish Kyphosus sydneyanus

Stomach content analysis showed that Kyphosus sydneyanus collected by spearing from coastal reefs near Leigh, north-east New Zealand, is herbivorous throughout its post-settlement life. All size classes collected consumed a wide range of macroalgae, predominantly the phaeophytes Carpophyllum maschalocarpum and Ecklonia radiata , and the rhodophytes Gigartina macrocarpa and Caulacanthus ustulatus . Multivariate analysis of variance and discriminant function analysis showed an ontogenetic diet shift, with gut contents dominated by rhodophytes and chlorophytes in juveniles and by phaeophytes in adults. No significant seasonal variation in diet was apparent for any size class. Amylase and amylopectinase activity was highest in the smaller size classes. Laminarinase activity was relatively low throughout all size classes, and did not correlate with the ontogenetic increase in phaeophyte consumption. The activity of endogenous enzymes hydrolysing starch broadly correlated with rhodophyte consumption in adult specimens of three other species of marine herbivorous fishes: Odax pullus, Girella tricuspidata and Parma alboscapularis; laminarin hydrolysis, however, was negatively correlated with phaeophyte consumption. Overall, the diet and enzyme results suggest that juvenile K. sydneyanus rely mainly on the endogenous digestion of rhodophytes and chlorophytes, while exogenous (microbial) digestion is used to digest the phaeophyte-dominated diet of adults.     

Ontogenetic Development of the Gastrointestinal Microbiota in the Marine Herbivorous Fish Kyphosus sydneyanus

Molecular techniques were used to investigate the composition and ontogenetic development of the intestinal bacterial community in the marine herbivorous fish Kyphosus sydneyanus from the north eastern coast of New Zealand. Previous work showed that K. sydneyanus maintains an exclusively algivorous diet throughout post-settlement life and passes through an ontogenetic diet shift from a juvenile diet which is readily digestible to an adult diet high in refractory algal metabolites. Terminal restriction fragment length polymorphism (T-RFLP) analysis was used to investigate the relationship between bacterial community structure and fish size. Bacterial diversity was higher in posterior gut sections than anterior gut sections, and in larger fish than in smaller fish. Partial sequencing of bacterial 16S rDNA genes PCR amplified and cloned from intestine content samples was used to identify the phylogenetic affiliation of dominant gastrointestinal bacteria. Phylogenetic analysis of clones showed that most formed a clade within the genus Clostridium, with one clone associated with the parasitic mycoplasmas. No bacteria were specific to a particular intestinal section or size class of host, though some appeared more dominant than others and were established in smaller fishes. Clones closely related to C. lituseburense were particularly dominant in most intestine content samples. All bacteria identified in the intestinal samples were phylogenetically related to those possessing fermentative type metabolism. Short-chain fatty acids in intestinal fluid samples increased from 15.6 ± 2.1 mM in fish <100 mm to 51.6 ± 5.5 mM in fish >300 mm. The findings of this study support the hypothesis that the ontogenetic diet shift of K. sydneyanus is accompanied by an increase in the diversity of intestinal microbial symbionts capable of degrading refractory algal metabolites into short-chain fatty acids, which can then be assimilated by the host.     

SEM study of the oral cavity of members of the Kyphosidae and Girellidae (Pisces,Teleostei), with remarks on Crenidens (Sparidae), focusing on teeth and taste bud numbers and distribution

The present study compares dental morphology and taste bud distribution in the oral cavity of four species of the teleost family Kyphosidae, five species of Girellidae and one species of Sparidae. Some of these species are predominantly herbivorous, while others are omnivorous with a high portion of invertebrates in their diets. All the kyphosids feature one row of frontal cusped teeth on their jaws and areas of miniature teeth on the tongue and palate; the girellid species feature 2–5 rows of denticulate teeth, and no teeth inside the oral cavity. The total number of taste buds in the oral cavity is higher in Girella spp. than in the kyphosids, and their number is species-specific, not correlated with fish size. For example, Kyphosus bigibbus of 500 mm standard length bears 1780 taste buds, while the kyphosid Neoscorpis lithophilus of 80 mm bears 3460. The maximum number of taste buds, 7900, is found in Girella punctata of 60 mm standard length, and the minimum number, 1320, in Kyphosus vaigiensis of 175 mm. The higher number of taste buds appears to characterize species that possess a more diversified diet. The present study contributes to our understanding of the differences between the two families Kyphosidae and Girellidae. In particular, it relates the eco-morphological adaptations to the type of diet consumed by the various species.     

Spatial variation and effects of habitat on temperate reef fish assemblages in northeastern New Zealand

Reef-associated fishes can respond to changes in habitat structure and the nature of their response can change with different spatial scales of observation. A structured hierarchical mensurative sampling design was used to sample temperate reef fish assemblages in northeastern New Zealand at several spatial scales over 2 years. The three spatial scales examined were tens of meters (transects), hundreds to thousands of meters (sites) and hundreds of kilometers (locations). We tested the hypothesis that fish assemblages differed between kelp forest habitat (relatively dense stands of the kelp, Ecklonia radiata (C. Agardh) J. Agardh, median depth=13.5 m) and barrens habitat (rocky reef dominated by turfing and encrusting red algae and the grazing urchin, Evechinus chloroticus (Valenciennes), median depth=6.7 m). Recently developed multivariate techniques were used to test for and quantify multivariate variation at different spatial scales. There were significant effects of habitat on the spatial distribution of fish assemblages, characterised by greater abundances or frequencies of Parika scaber, Chromis dispilus, Trachurus novaezelandiae, Nemadactylus douglasii, Bodianus unimaculatus, Odax pullus and Pseudolabrus miles in kelp forest habitat, and greater abundances or frequencies of Notolabrus celidotus, Notolabrus fucicola, Girella tricuspidata, Coris sandageri, Chironemus marmoratus, Parma alboscapularis, Scorpis violaceus and Kyphosus sydneyanus in barrens habitat. Some of the more common species, including Upeneichthys lineatus, Scorpis lineolatus and Cheilodactylus spectabilis showed no strong consistent effects of these two differing habitats on their distributions. There was, however, a significant Habitat×Locations interaction: effects of habitat did not occur at all locations. Variability was highest at the scale of individual transects and variability from site to site and from location to location was comparable. Spatial variation was large compared to inter-annual variation, which was minimal, and spatial patterns were consistent in the 2 years examined. Further experiments, including manipulations, are required to understand what mechanisms and processes might be driving these patterns. This study, coupled with results from previous studies, suggests that there may be a dynamic inter-play between effects of habitat on fish and effects of fish on biogenic habitat, such as kelp forests.     

Hindgut Fermentation in Three Species of Marine Herbivorous Fish

Symbioses with gut microorganisms provides a means by which terrestrial herbivores are able to obtain energy. These microorganisms ferment cell wall materials of plants to short-chain fatty acids (SCFA), which are then absorbed and used by the host animal. Many marine herbivorous fishes contain SCFA (predominantly acetate) in their hindgut, indicative of gut microbial activity, but rates of SCFA production have not been measured. Such information is an important prerequisite to understanding the contribution that gut microorganisms make in satisfying the energy needs of the fish. We have estimated the rates of acetate production in the gut of three species of temperate marine herbivorous fish from northeastern New Zealand: Kyphosus sydneyanus (family Kyphosidae), Odax pullus (family Odacidae), and Aplodactylus arctidens (family Aplodactylidae). Ex vivo preparations of freshly caught fish were maintained with their respiratory and circulatory systems intact, radiolabeled acetate was injected into ligated hindgut sections, and gut fluid was sampled at 20-min intervals for 2 h. Ranges for acetate turnover in the hindguts of the studied species were determined from the slope of plots as the log of the specific radioactivity of acetate versus time and pool size, expressed on a nanomole per milliliter per minute basis. Values were 450 to 570 (K. sydneyanus), 373 to 551 (O. pullus), and 130 to 312 (A. arctidens). These rates are comparable to those found in the guts of herbivorous reptiles and mammals. To determine the contribution of metabolic pathways to the fate of acetate, rates of sulfate reduction and methanogenesis were measured in the fore-, mid-, and hindgut sections of the three fish species. Both rates increased from the distal to proximal end of the hindgut, where sulfate reduction accounted for only a small proportion (<5%) of acetate methyl group transformed to CO₂, and exceeded methanogenesis from acetate by >50-fold. When gut size was taken into account, acetate uptake from the hindgut of the fish species, determined on a millimole per day per kilogram of body weight basis, was 70 (K. sydneyanus), 18 (O. pullus), and 10 (A. arctidens).     

Arrival sequence and diet mediate interspecific competition in an ant community

The arrival sequence of organisms in a habitat and their diet are two factors that are thought to modulate animal performance, affect the outcome of behavioural interactions, and shape communities. In New Zealand, two species that seldom co-occur in field populations are Prolasius advenus and Monomorium antarcticum. Herein we tested the hypotheses that arrival sequence and diet influence the strength of interactions between these two species. These ant species presented asymmetric responses to arrival sequence and diet variations. When arriving first P. advenus displayed increased aggression and M. antarcticum a defensive reaction. Changes in carbohydrate and protein availability modulated colony activity rates of both species. Colonies of M. antarcticum fed on a high carbohydrate and low protein diet displayed higher activity rates than colonies fed on a low carbohydrate and high protein diet. In contrast, control colonies of P. advenus fed on a high carbohydrate and low protein diet displayed lower activity rates than colonies fed on a low carbohydrate and high protein diet. These results indicate that arrival sequence can modulate the agonistic reaction displayed by interacting species in situations of conflict. This work also demonstrates that species adjust activity rates in response to diet, but different species do so differently. Therefore, arrival sequence and diet could explain species mutually exclusive distribution patterns observed in nature.     

Diversity among Macroalgae-Consuming Fishes on Coral Reefs: A Transcontinental Comparison

Despite high diversity and abundance of nominally herbivorous fishes on coral reefs, recent studies indicate that only a small subset of taxa are capable of removing dominant macroalgae once these become established. This limited functional redundancy highlights the potential vulnerability of coral reefs to disturbance and stresses the need to assess the functional role of individual species of herbivores. However, our knowledge of species-specific patterns in macroalgal consumption is limited geographically, and there is a need to determine the extent to which patterns observed in specific reefs can be generalised at larger spatial scales. In this study, video cameras were used to quantify rates of macroalgae consumption by fishes in two coral reefs located at a similar latitude in opposite sides of Australia: the Keppel Islands in the Great Barrier Reef (eastern coast) and Ningaloo Reef (western coast). The community of nominally herbivorous fish was also characterised in both systems to determine whether potential differences in the species observed feeding on macroalgae were related to spatial dissimilarities in herbivore community composition. The total number of species observed biting on the dominant brown alga Sargassum myriocystum differed dramatically among the two systems, with 23 species feeding in Ningaloo, compared with just 8 in the Keppel Islands. Strong differences were also found in the species composition and total biomass of nominally herbivorous fish, which was an order of magnitude higher in Ningaloo. However, despite such marked differences in the diversity, biomass, and community composition of resident herbivorous fishes, Sargassum consumption was dominated by only four species in both systems, with Naso unicornis and Kyphosus vaigiensis consistently emerging as dominant feeders of macroalgae.     

The relative impacts of grazing by caribbean coral reef fishes and Diadema: effects of habitat and surge

The effects of grazing on fleshy algal turfs by large herbivorous fishes and by the black spiny urchin, Diadema antillarum (Philippi), were investigated in three shallow (<3 m), moderately exposed, reef flat habitats in the San Blas Islands on the Caribbean coast of Panama. Grazing by Diadema was found to be a primary determinant of the biomass of fleshy algae in this shallow reef environment, and its impact was exposure-dependent. Feeding activity of Diadema was inhibited during the protracted periods of heavy wave action that characterize the dry season when strong north winds (24–27 kph) are typical. In the shallowest, most exposed elkhorn bluff habitats urchin grazing was minimal even during calm periods due to the effects of waves generated by unpredictable, light winds. In a relatively protected backreef habitat, water movement was inadequate to discourage grazing significantly, even during the turbulent dry season. As a result, algal biomass (decalcified dry weight) was typically three-fold greater in the elkhorn bluff habitat than on the ackreef. In habitats of intermediate exposure (elkhorn fields) algal biomass was reduced during calm periods, but increased to the level characteristic of the elkhorn bluff habitat during protracted rough periods that inhibited grazing by Diadema.A caging experiment in the backreef habitat demonstrated a relatively minor effect of grazing by herbivorous fishes in comparison to that of grazing by Diadema. Observations on the distributions and abundances of herbivorous fishes also indicated a relatively minor role for these grazers as determinants of algal biomass in the more exposed habitats.     

Beetles in the diet of six species of deep‐sea fish

Abstract

Four scarab beetles (Acrossidius tasmaniae) and two unidentified weevils were recovered from the guts of a single individual of six deep‐sea fishes trawled from depths of 326–418 m, c. 30–40 km off the Wairarapa coast, North Island, New Zealand. These constitute the first records of terrestrial arthropods in the diet of deep‐sea fishes from the New Zealand region. Possible reasons describing how these terrestrial beetles came to be eaten by these fishes are discussed.     

Effect of UV radiation on habitat selection by Girella laevifrons and Graus nigra (Kyphosidae)

The effect of UV radiation on habitat use of two species of intertidal fishes that inhabit the same pools but exhibit different activity levels and diets was measured: the highly active omnivorous Girella laevifrons and the cryptic carnivorous Graus nigra. Individuals of each species were acclimated to a tank divided in three sections with different illumination; no light (NL), ultraviolet light (UV) and white light (WL), and the time spent and number of visits to each section were recorded. Although both species preferred the NL section, G. laevifrons spent more time in UV and less time in WL compared with G. nigra; G. laevifrons also displayed higher number of visits to UV, suggesting a different tendency in space use in response to UV exposure in intertidal fishes.     

Contrasting digestive strategies in four New Zealand herbivorous fishes as reflected by carbohydrase activity profiles

Enzymatic degradation of algal carbohydrates was examined in the New Zealand herbivorous fishes Parma alboscapularis (Pomacentridae), Aplodactylus etheridgii (Aplodactylidae), Girella tricuspidata and G. cyanea (Girellidae). Enzyme extract taken from the anterior gut wall, gut fluid and microbial pellet from sections sampled along the gut were tested for activity against starch, carrageenan, agarose and carboxymethylcellulose. Hydrolysis of starch was greater than for all other substrates tested. Endogenous (host-produced) activity in the anterior gut fluid varied between species in the order G. tricuspidata (7700 units mL(-1))>G. cyanea (2300 units mL(-1))>P. alboscapularis (2000)>A. etheridgii (1400 units mL(-1)) where one unit is equivalent to 1 mug of reducing sugar released per minute. Activity decreased markedly along the gut in all cases, so that at the posterior end of the gut only 0.3-8% of the anterior activity remained in the gut fluid. Enzyme activity against structural carbohydrates was lower than that against starch, and was of exogenous (produced by resident microbiota) origin in all species although the location of activity along the gut differed. The microbial extract of A. etheridgii displayed the highest activity against carrageenan and agarose in all gut sections, reaching maxima of 47 units mL(-1) against carrageenan and 35 units mL(-1) against agarose in the mid-gut microbial extract. Carrageenase and agarase activity in the other three species was <10 units mL(-1) for all gut sections. Results suggest that carrageenan and agarose are potentially important substrates for microbial fermentation, particularly in A. etheridgii, and that there is microbial activity in the mid-gut of this species, rather than primarily in the hind-gut as in other herbivorous species.     

Pterostilbene,a dimethylated analog of resveratrol,promotes energy metabolism in obese rats

Pterostilbene (trans-3,5-dimethoxy-4-hydroxystilbene) is a dimethylated analog of resveratrol and has been reported to exert various pharmacological effects. In this study, we evaluated the effect of pterostilbene on the pathogenesis of obesity and energy metabolism in obese rats.Pterostilbene significantly activates silent mating type information regulation 2 homolog-1 and peroxisome proliferator-activated receptor-alpha in vitro. At 4 weeks a 0.5% pterostilbene diet markedly suppressed the abdominal white adipose tissue (WAT) accumulation in obese rats. The oxygen consumption and energy expenditure were significantly higher in the pterostilbene group, and pterostilbene increased the fat metabolism rather than the carbohydrate metabolism in obese rats. The mRNA level of uncoupling protein, a thermogenic regulator, was increased and the mRNA levels of fatty acid synthase and leptin, which are involved in lipogenesis and fat storage, were markedly decreased in WAT after the pterostilbene feeding. These results suggest that pterostilbene prevents WAT accumulation through the enhancement of energy metabolism and partly the suppression of lipogenesis in obese OLETF rats.     

A review of the biology and ecology of key fishes targeted by coastal fisheries in south-east Australia: identifying critical knowledge gaps required to improve spatial management

Knowledge of the population biology, life-history ecology and scales of pre and post-settlement movement of marine species are needed to inform effective conservation management strategies, particularly when spatial information is required for management purposes such as zoning in Marine Protected Areas. This review provides the most current summary from primary and grey literature on the biology and ecology of several coastal fishes of economic and ecological significance in south-east Australia; identifies key knowledge gaps which may impede the development of effective spatial management; and recommends future research directions and methods. Reviewed species are luderick (Girella tricuspidata), eastern rock blackfish (Girella elevata), yellowfin bream (Acanthopagrus australis), tarwhine (Rhabdosargus sarba), snapper (Pagrus auratus), red morwong (Cheilodactylus fuscus) and eastern blue grouper (Achoerodus viridis). The species have a diverse range of life-histories and population traits, and selected parameters were well studied in several species, such as growth (blue groper, luderick, yellowfin bream, tarwhine, snapper), post-settlement movement (red morwong), and larval ecology (yellowfin bream). However, empirical data on levels of pre- and post-settlement connectivity and real-time movements are not available for most species, and this represents a significant gap for improved spatial management. A multidisciplinary approach incorporating a range of methods including acoustic tracking and telemetry, otolith chemistry, intergenerational markers, and biophysical modelling will provide a more comprehensive understanding of life history parameters, movement and connectivity at scales relevant to MPA planning and monitoring.     

Physiological responses to short-term fasting among herbivorous,omnivorous, and carnivorous fishes

We explored the integrated role of dietary specialization and feeding periodicity on the response of the gastrointestinal tract of teleosts fishes to short-term (7–10 days) fasting and refeeding. Fasted and fed herbivorous grass carp (Ctenopharyngodon idella), omnivorous channel catfish (Ictalurus punctatus), and carnivorous largemouth bass (Micropterus salmoides) were compared for digestive organ masses, intestinal morphology, gastrointestinal pH, and the specific activities and total intestinal capacities of the intestinal hydrolases aminopeptidase (APN) and maltase and intestinal nutrient transporters. All three species experience intestinal hypertrophy with feeding as noted by significant increases in enterocyte dimensions. Of the three, only I. punctatus experienced a postprandial increase in intestinal length, and only C. idella experienced significant modulation of intestinal microvillus length. Feeding resulted in acidification of the stomachs of I. punctatus and M. salmoides. Predicted to exhibit a relatively modest set of postprandial responses because of their more frequent feeding habits, C. idella only experienced increases in APN and maltase activity with feeding and no significant regulation of nutrient uptake. Significant regulation of hydrolase activities and nutrient uptake were exhibited by I. punctatus and M. salmoides, with I. punctatus experiencing the most comprehensive set of responses. As predicted by food habits, there was an interspecific gradient in intestinal length and glucose uptake extending from longer intestines and greater glucose uptake for the herbivorous C. idella, intermediate lengths and glucose uptake for the omnivorous I. punctatus, and shorter intestines and reduced glucose uptake for the carnivorous M. salmoides. Among teleosts fishes, short episodes of fasting lead to significant alterations in intestinal form and function that are rapidly restored with feeding.     

Reversal of obesity-induced hypertriglyceridemia by (R)-α-lipoic acid in ZDF (fa/fa) rats

Controlling elevated blood triacylglycerol translates into substantial health benefits. The present study aimed to evaluate the triacylglycerol-lowering properties of (R)-α-lipoic acid (LA) once circulating triacylglycerol levels have become elevated, and identify the molecular targets of LA. Nine-week old male ZDF (fa/fa) rats were fed a chow diet supplemented with 3 g LA per kg diet or pair fed for two weeks (8 rats per treatment). We determined changes in blood triacylglycerol, insulin, non-esterified fatty acids, and ketone bodies concentrations. We analyzed the expression of genes and proteins involved in fatty acid and triacylglycerol metabolism in liver, epididymal fat, and skeletal muscle. Feeding LA to ZDF rats (a) corrected severe hypertriglyceridemia, (b) lowered abdominal fat mass, (c) raised circulating fibroblast growth factor-21 and Fgf21 liver gene expression, (d) repressed lipogenic gene expression of ATP-citrate synthase (Acly), acetyl-coA carboxylase 1 (Acaca), fatty acid synthase (Fasn), sn-glycerol-3-phosphate acyltransferase 1 (Gpam), adiponutrin (Pnpla3) in the liver and adipose tissue, (e) decreased hepatic protein levels of ACC1/2, FASN and 5′-AMP-activated protein kinase catalytic subunit α (AMPKα), (f) did not change phospho-AMPKα/AMPKα and phospho-ACC/ACC ratios, (g) stimulated liver gene expression of PPARα target genes carnitine O-palmitoyltransferase 1β (Cpt1b) and acyl-CoA thioesterase 1 (Acot1) but not carnitine O-palmitoyltransferase 1α (Cpt1a). This is evidence that short-term LA feeding to obese rats reverses severe hypertriglyceridemia. FGF21 may mediate the beneficial metabolic effects of LA.     

Isocaloric manipulation of macronutrients within a high-carbohydrate/moderate-fat diet induces unique effects on hepatic lipogenesis,steatosis and liver injury

Diets containing excess carbohydrate and fat promote hepatic steatosis and steatohepatitis in mice. Little is known, however, about the impact of specific carbohydrate/fat combinations on liver outcome. This study was designed to determine whether high-energy diets with identical caloric density but different carbohydrate and fat composition have unique effects on the liver. Four experimental diets were formulated with 60% kcal carbohydrate and 20% kcal fat, each in nearly pure form from a single source: starch-oleate, starch-palmitate, sucrose-oleate and sucrose-palmitate. The diets were fed to mice for 3 or 12 weeks for analysis of lipid metabolism and liver injury. All mice developed hepatic steatosis over 12 weeks, but mice fed the sucrose-palmitate diet accumulated more hepatic lipid than those in the other three experimental groups. The exaggerated lipid accumulation in sucrose-palmitate-fed mice was attributable to a disproportionate rise in hepatic de novo lipogenesis. These mice accrued more hepatic palmitate and exhibited more evidence of liver injury than any of the other experimental groups. Interestingly, lipogenic gene expression in mice fed the custom diets did not correlate with actual de novo lipogenesis. In addition, de novo lipogenesis rose in all mice between 3 and 12 weeks, without feedback inhibition from hepatic steatosis. The pairing of simple sugar (sucrose) and saturated fat (palmitate) in a high-carbohydrate/moderate-fat diet induces more de novo lipogenesis and liver injury than other carbohydrate/fat combinations. Diet-induced liver injury correlates positively with hepatic de novo lipogenesis and is not predictable by isolated analysis of lipogenic gene expression.     

Trophic Interactions and Distribution of Some Squaliforme Sharks,Including New Diet Descriptions for Deania calcea and Squalus acanthias

Squaliforme sharks are a common but relatively vulnerable bycatch in many deep water fisheries. Eleven species of squaliforme shark are commonly caught at depths of 200–1200 m on Chatham Rise, New Zealand, and their diversity suggests they might occupy different niches. The diets of 133 Deania calcea and 295 Squalus acanthias were determined from examination of stomach contents. The diet of D. calcea was characterised by mesopelagic fishes, and S. acanthias by benthic to pelagic fishes, but was more adaptive and included likely scavenging. Multivariate analyses found the most important predictors of diet variability in S. acanthias were year, bottom temperature, longitude, and fish weight. The diet of the nine other commonly caught squaliforme sharks was reviewed, and the spatial and depth distribution of all species on Chatham Rise described from research bottom trawl survey catches. The eleven species had a variety of different diets, and depth and location preferences, consistent with niche separation to reduce interspecific competition. Four trophic groups were identified, characterised by: mesopelagic fishes and invertebrates (Centroselachus crepidater, D. calcea, and Etmopterus lucifer); mesopelagic and benthopelagic fishes and invertebrates (Centroscymnus owstoni, Etmopterus baxteri); demersal and benthic fishes (Centrophorus squamosus, Dalatias licha, Proscymnodon plunketi); and a generalist diet of fishes and invertebrates (S. acanthias). The trophic levels of the species in each of the four groups were estimated as 4.18–4.24, 4.20–4.23, 4.24–4.48, and 3.84 respectively. The diet of Oxynotus bruniensis and Squalus griffini are unknown. The different niches occupied by different species are likely to influence their vulnerability to bottom trawl fisheries. Some species may benefit from fisheries through an increased availability of scavenged prey.