Influence of seasonal food abundance and quality on the feeding habits of an opportunistic feeder,the intertidal crab <Emphasis Type="Italic">Pachygrapsus marmoratus</Emphasis>

The abundance of trophic sources on the intertidal zone is discontinuous and their supply can vary both in a predictable or unpredictable way. The Mediterranean semi-terrestrial crab Pachygrapsus marmoratus, is known, as adult, to entirely rely on the intertidal trophic sources, and, consequently, it faces the fluctuations of nutritional sources and quality. To clarify the relationships between the feeding habits of an Italian population of P. marmoratus and the temporal variation of its food sources, we carried out a 2-year sampling protocol. Data on seasonal variation in composition of intertidal food item assemblages, on the average content in N and C of the commonest algae, on seasonal changes in crabs feeding habits were collected and compared using a suite of multivariate and univariate techniques. Results showed that P. marmoratus takes advantage of the recruitment phase of the most common invertebrates, affecting and controlling the abundance even of those species whose adults are out of its reach. It can act both as a herbivore, and as a carnivore that shifts between bivalves, more abundant in spring/summer, and the periwinkle Melaraphe neritoides, during winter. In conclusion, we provide evidences on the food choice of this common rocky shore species, which is very plastic and capable of relying on many trophic sources, possibly influencing the abundance and/or the population structure of a number of intertidal populations.     

Effect of temperature on activity and social behavior of the adult tautog Tautoga onitis under laboratory conditions

Experiments were conducted on the effects of high, sublethal temperature on activity, social behavior, and feeding in the adult tautog Tautoga onitis held under controlled laboratory conditions. Norms of these behaviors were established during acclimation to temperatures at which these fish are commonly found. During acclimation, the fish were active and feeding throughout the day. A dominance hierarchy, based primarily on size, was established for each group, with subordinate fish being displaced from all areas of the aquarium. Under elevated temperature, changes in established norms of these behaviors were observed, with activity, feeding, aggression, and the spacing between fish showing a decrease. Following return to pre-rise temperatures, although aggression remained reduced, activity, interfish distance, and feeding approached levels established during acclimation. A comparison of these results with previous ones on young tautog is made and the significance of the findings is discussed.This work was supported, in part, by a grant from the U.S. Energy Research and Development Administration No. E(49-7) 3045.     

Mechanisms of benthic prey capture in wrasses (Labridae)

Teleost fishes capture prey using ram, suction, and biting behaviors. The relative use of these behaviors in feeding on midwater prey is well studied, but few attempts have been made to determine how benthic prey are captured. This issue was addressed in the wrasses (Labridae), a trophically diverse lineage of marine reef fishes that feed extensively on prey that take refuge in the benthos. Most species possess strong jaws with stout conical teeth that appear well-suited to gripping prey. Mechanisms of prey capture were evaluated in five species encompassing a diversity of feeding ecologies: Choerodon anchorago (Bloch, 1791), Coris gaimard (Quoy and Gaimard, 1824), Hologymnosus doliatus (Lacepède, 1801), Novaculichthys taeniourus (Lacepède, 1801) and Oxycheilinus digrammus (Lacepède, 1801). Prey capture sequences were filmed with high-speed video at the Lizard Island Field Station (14°40′S, 145°28′E) during April and May 1998. Recordings were made of feeding on pieces of prawn suspended in the midwater and similar pieces of prawn held in a clip that was fixed to the substratum. Variation was quantified among species and between prey types for kinematic variables describing the magnitude and timing of jaw, hyoid, and head motion. Species differed in prey capture kinematics with mean values of most variables ranging between two and four-fold among species and angular velocity of the opening jaw differing seven-fold. The kinematics of attached prey feeding could be differentiated from that of midwater captures on the basis of faster angular velocities of the jaws and smaller movements of cranial structures which were of shorter duration. All five species used ram and suction in combination during the capture of midwater prey. Surprisingly, ram and suction also dominated feedings on attached prey, with only one species making greater use of biting than suction to remove attached prey. These data suggest an important role for suction in the capture of benthic prey by wrasses. Trade-offs in skull design associated with suction and biting may be particularly relevant to understanding the evolution of feeding mechanisms in this group. Published online: 11 July 2002     

A comparison of strike and prey capture kinematics of three species of piscivorous fishes: Florida gar ( Lepisosteus platyrhincus), redfin needlefish ( Strongylura notata), and great barracuda ( Sphyraena barracuda)

Ram feeding is the process by which a predatory fish uses a high-velocity lunge or chase to overtake its prey. This study compares the strike and prey capture behaviors and kinematics of three species of ram-feeding fishes: Florida gar Lepisosteus platyrhincus, redfin needlefish Strongylura notata, and great barracuda Sphyraena barracuda. These ram-feeding piscivores are morphologically similar with fusiform bodies, posteriorly placed dorsal and anal fins, and large, conical teeth. Strike and prey capture kinematics for five individuals of each species were recorded with high-speed video. Pre-strike behavior in L. platyrhincus consists of a slow stalk, resulting in the close, lateral positioning of the predators head relative to the prey. Lepisosteus employ a sideways lunge of the head during the strike, which lasts only 25–40 ms and is the most rapid strike among these three species. Strongylura notata and Sphyraena barracuda exhibit longitudinal orientation to the prey before the strike, followed by a high velocity, head-on lunge, initiated by an s-start in Sphyraena barracuda. Prey capture in adult L. platyrhincus and Strongylura notata is characterized by the jaws closing on the prey, with the prey held orthogonal to the jaws. This is followed by manipulation using the inertia of the prey to reposition the prey head first, and then suction transport into the buccal cavity. Prey capture in juvenile Sphyraena is accomplished by closing the jaws after the prey has entered the buccal cavity, resulting in possible ram transport of the prey with no oral manipulation under these experimental conditions. Although these three species all employ ram feeding for prey capture of elusive prey, each species has a unique repertoire that appears to minimize hydrodynamic constraints and prey response, utilize locomotory capabilities, and may be suited to each species specific habitat.Communicated by P.W. Sammarco, Chauvin     

Correlates between number of mates,shelter availability and reproductive behavior in the Tautog Tautoga onitis

Earlier studies on reproductive behavior of the tautog Tautoga onitis under laboratory conditions indicated that differences in courtship and spawning behavior were apparently related to the number of males attempting to spawn with a female. It had also been conjectured that certain ecological factors such as availability and distribution of food and shelter would play a role in the establishment of territoriality and defense of a female, indirectly influencing courtship activities and the resultant spawning mode. In the present work we have examined this question more closely by varying the number of males, females and amount of shelter available. Regardless of the social situation, in every instance single males, through aggression, attempted to limit access to a female and pair spawn. The degree to which this succeeded depended on the male's place in the dominance hierarchy, the number of males in proximity which were actively attempting to spawn and the availability of shelter. Courtship activity of the female was influenced by the amount of male attention. When attention was high, the nuptial shading of the female never developed maximally. On the other hand, when male attention was low, the female showed progressive and maximal shading development to attract males. The significance of the findings is discussed.     

Role of temperature in triggering migratory behavior of the adult tautog Tautoga onitis under laboratory conditions

Adult tautog Tautoga onitis, a marine temperate-water labrid, migrate each fall from inshore summering grounds to offshore overwintering sites. In a previous laboratory study, when adults were held under natural fall-winter cycles of temperature and photoperiod, changes in behavior, indicative of migration, occurred at the same time as their fall migration in nature. In the present study when fish were held under natural photoperiod in summer but with decreasing fall-winter temperature, while highly variable and transient components of migratory behavior were observed, no sustained trend was evident. Then, in the fall, under a naturally changing photoperiod but at simulated summer temperature, no trace of migratory behavior was observed. These findings indicate that temperature appears to play a leading role in triggering the fall migration of the species. The significance of these results and their ecological implications is discussed.     

Diet and food preferences of the adult horseshoe crab Limulus polyphemus in Delaware Bay,New Jersey,USA

Adult horseshoe crabs Limulus polyphemus (L.) feed on a wide variety of infaunal and epifaunal invertebrates during their spring spawning migration in Delaware Bay, New Jersey, USA. Comparison of the gut contents with estimates of available prey showed that the most abundant potential prey item, the bivalve Gemma gemma, was avoided. The thinner shelled but comparatively scarce clam Mulinia lateralis was a preferred prey item. In the laboratory, crabs fed on G. gemma when it was the only available item but not when M. lateralis or soft-shell clams, Mya arenaria, were offered in conjunction. Large M. lateralis (>10mm) were preferred to small M. lateralis; there was no discrimination between M. lateralis and M. arenaria of the same size. Male and female horseshoe crabs had similar gut contents and laboratory feeding preferences, despite the fact that females are larger than males. Crabs spawning later in the summer contained more food than did crabs collected at the peak of spawning activity.     

Reduced planktotrophy in larvae of <Emphasis Type="Italic">Clypeaster</Emphasis><Emphasis Type="Italic">rosaceus</Emphasis> (Echinodermata,Echiniodea)

Phylogenetic analyses have demonstrated that nonfeeding larvae have evolved from feeding larvae many times among marine invertebrates. In light of this observation, it is surprising that an intermediate strategy, a larva that can feed but is provisioned with enough energy to metamorphose without acquiring exogenous food (i.e., facultative planktotrophy), is rare. A hypothesis for the lack of facultative planktotrophic species among marine invertebrates is that the transition from feeding to nonfeeding is rapid due to this intermediate stage being evolutionarily unstable. Evidence that would support this hypothesis is if species with facultative planktotrophy have reduced food assimilation when compared with obligate planktotrophs. We studied a species with facultative planktotrophic larvae, Clypeaster rosaceus, that is very near the boundary between facultative and obligatory planktotrophy, to answer two questions: (1) does feeding during the larval stage result in energy gains in larval or juvenile stages and (2) if not, are larvae capable of assimilating exogenous food at all. Our measurements of energetics in larval and juvenile stages show that C. rosaceus larvae accumulate very little if any energy when fed, but stable isotope data indicate that larvae are able to assimilate some food. Our results are consistent with similar studies on facultative planktotrophic larvae suggesting poor food assimilation and rapid loss of larval feeding after a population evolves the ability to reach metamorphosis without feeding (lecithotrophy).     

Stable isotope analysis of two species of anguilliform leptocephali (<Emphasis Type="Italic">Anguilla japonica</Emphasis> and <Emphasis Type="Italic">Ariosoma major</Emphasis>) relative to their feeding depth in the North Equatorial Current region

Anguilla japonica leptocephali are transported from their offshore spawning area to their recruitment areas in East Asia, but their depth distributions, food sources and feeding are still poorly known. This study analyzed carbon and nitrogen stable isotope ratios of leptocephali of A. japonica, Ariosoma major and Ariosoma spp., and of particulate organic matter (POM), their likely food source, at five different depths in 2004–2009. We used mixing models to show that A. japonica appeared to be feeding at depths between 5 and 50 m, but sometimes deeper. A. major appeared to have a tendency of mostly feeding at depths of 50 m or shallower. Although the A. japonica and Ariosoma spp. collected in the same area during the leptocephalus stage appeared to have different feeding ecologies possibly related to different types of POM, their different depth distributions, sizes and transport histories may also help explain these differences.     

Behavior of juvenile American lobsters, Homarus americanus, under predation risk

The influence of predation risk and food deprivation on the behavior and activity of juvenile American lobsters, Homarus americanus Milne Edwards, was examined in single and paired individuals in laboratory experiments performed during 1988 and in the winter of 1991/92. In the presence of a predator (the tautog Tautoga onitis Linnaeus) restrained behind a barrier, single lobsters significantly reduced the time spent feeding at night, consumed fewer mussels, and quickly brought them back to shelter. Single lobsters did not forage during the day in any treatment. If deprived of food for 60 h, they consumed more mussels and spent more time walking than recently fed (12-h food-deprived) lobsters. Paired lobsters did forage during the day in the presence of a predator. The smaller lobsters (subdominant) in the pairs foraged for a longer time in the presence than in the absence of a predator and significantly longer than single individuals. Shelter occupancy was significantly shorter in single, recently fed lobsters in the presence of a predator compared to time spent sheltering in its absence. Among food-deprived lobsters, paired individuals spent a significantly shorter time within the shelter than single lobsters in the absence of a predator. Larger (dominant) lobsters, however, spent more time than subdominant lobsters within the shelter during all periods of the day. Without a predator, paired lobsters spent significantly more time than single ones in shelter-related activities. Under predation risk, subdominant lobsters concentrated shelter-building time during the day and built a higher percent of alternative shelters than either single or dominant lobsters. In the absence of a predator, paired lobsters walked in the open area for a significantly longer time than single ones in the absence of a predator. This apparently was associated with fighting between dominant and subdominant lobsters and the attempts of the larger lobster to drive the smaller one from its shelter. During the day, lobsters fought for a significantly longer time in the presence than in the absence of a predator. When the tautog was not constrained, mortality rate was similar in both single and paired lobsters. Mortality rate among subdominant lobsters, however, was seven times higher than among dominant lobsters. We suggest that the risk of predation interferes with the ability of single juvenile lobsters to acquire and consume food. They appear to trade off energetic consideration against risk of predation when foraging away from the shelter. The introduction of a conspecific competitor to the system may further increase risk (of the subdominant) to the predator. Intraspecific interactions tend to increase the risk of predation to smaller lobsters but increase the survival rate among larger lobsters. Received: 6 February 1995 / Accepted: 2 September 1997     

Diets of fishes of the upper continental slope of eastern Tasmania: content,calorific values,dietary overlap and trophic relationships

Diets of 15 species of demersal and pelagic fishes on the upper continental slope (420 to 550 m) were determined, based on samples taken every two months over 13 mo (April 1984 to April 1985) off eastern Tasmania. The calorific contribution of each prey item to the diets was determined. The fish could be divided into four trophic categories: pelagic piscivores, epibenthic piscivores, epibenthic invertebrate feeders and benthopelagic omnivores. Dietary overlap between the groups was low. The pelagic piscivores Apogonops anomalus, Trachurus declivis, Brama brama, Lepidopus caudatus and Macruronus novaezelandiae primarily consume the shelf-break myctophid Lampanyctodes hectoris; their diet is narrow, with a large overlap between species. The epibenthic piscivores Deania calcea and Genypterus blacodes both take a greater variety of prey, but have little dietary overlap. The fish feeding on epibenthic invertebrates, Coelorinchus sp. 2 and Centriscops humerosus, obtain most of their energy from benthic Crustacea and Ophiuroidea, supplemented with Lampanyctodes hectoris; the diet is broad, with little overlap. Among the benthopelagic omnivores (Cyttus traversi, Coelorinchus sp. 4, Lepidorhynchus denticulatus, Neocyttus rhomboidalis, Helicolenus percoides, Epigonus denticulatus and E. lenimen), most diets are broad and show slight overlap. All but E. denticulatus consume significant quantities of Lampanyctodes hectoris as well as Crustacea, particularly Polychaeta, Euphausiacea and Pyrosoma atlanticum. Seasonal changes in diet occurred in G. blacodes, T. declivis, Lepidopus caudatus, Coelorinchus sp. 4, Lepidorhynchus denticulatus, H. percoides, E. denticulatus and E. lenimen; these were related to changes in abundance of particular prey species, not to alterations in feeding habits. Only three species, Lepidopus caudatus, Coelorinchus sp. 2 and H. percoides, showed significant diel feeding periodicity. Ontogenetic dietary changes were evident in Cyttus traversi, Coelorinchus sp. 2, Lepidorhynchus denticulatus and H. percoides. Cyttus traversi and H. percoides progressively changed from crustaceans to fish as their size increased. The diets of size classes within species showed little overlap, except for Lepidorhynchus denticulatus, which eats chiefly euphausiids and Lampanyctodes hectoris at all sizes. In addition to describing the diets and trophic relationships of 90% of the fish biomass, the results emphasize the importance to the entire fish community of mesopelagic food resources, particularly Lampanyctodes hectoris. Many benthopelagic species undertake extensive vertical migrations in search of prey, thus playing a major role in the transport of energy from midwater regions to the benthos of the continental slope.     

Seasonal variations in the stable carbon and nitrogen isotope ratios (13C/12C and 15N/14N) of primary producers and consumers in a western Mediterranean coastal lagoon

Stable carbon and nitrogen isotope ratios (¹³C/¹²C and ¹⁵N/¹⁴N) of primary producers and consumers were investigated seasonally throughout 1999, in order to describe the food web in a western Mediterranean coastal lagoon (Lake of Sabaudia, central Italy). Particulate organic matter and algal material (seagrass epiphytes and macroalgae) seem to constitute the main food sources for primary consumers (zooplankton and small benthic invertebrates, respectively) throughout the sampling year, while the seagrass Cymodocea nodosa appears to play a negligible trophic role. As regards the ichthyofauna, carbon stable isotopes differentiated between planktivore and benthivore fish species. However, a benthic-pelagic coupling seems to occur, with some fish of higher trophic levels feeding both on benthic and pelagic materials. Analysis of variance showed that the interaction between the three main factors (species2size2season) significantly affects the isotopic composition of fish, suggesting the presence of intra- and inter-specific resource partitioning. Wide seasonal variations in the isotopic composition were observed in organic matter sources, invertebrates and fish, with a general trend towards depleted values in winter and enriched values in summer. The winter depletion of organic matter sources may be due to several environmental factors and seems to be mirrored in the upper trophic levels. Primary producers and invertebrates are known to have shorter time-integrated isotopic signatures than vertebrates, yet fish also exhibited seasonal isotopic differences. We concluded that the examined fish species can assume a new muscle isotopic signature relatively quickly in response to changes in the isotopic composition of their diet and/or diet shifts.     

Trophic ecology of coral reef gobies: interspecific,ontogenetic, and seasonal comparison of diet and feeding intensity

In fishes, a small body size may facilitate cost-effective exploitation of various primary and secondary food resources, but may pose difficulties associated with digestion of plant material and finding sufficient food in a foraging area potentially restricted by a high risk of predation. We examined the trophic ecology of five common, small-bodied coral reef fish from the family Gobiidae. For each species, we determined diet composition, feeding bite rate, foraging substrate, and feeding behaviour, and examined whether diet composition and feeding bite rate changed ontogenetically and seasonally. The five species showed a diverse range of trophic modes: Amblygobius bynoensis and Amblygobius phalaena were herbivores, Valenciennea muralis was a carnivore, Asterropteryx semipunctatus a detritivore, and Istigobius goldmanni an omnivore. Both the herbivores and detritivore supplemented their diet with animal material. The consumption of a wide range of dietary resources by the two smallest species with the most restricted mobility (A. semipunctatus and I. goldmanni) may ensure energy requirements are met within a restricted foraging area. There was a significant difference in mean feeding bite rate among species, with carnivore > herbivore > omnivore > detritivore. None of the species exhibited an ontogenetic shift in diet composition or increase in feeding bite rate, indicating that (1) postmaturation growth is not facilitated by a higher quality diet or increased feeding intensity following maturation, and (2) their small body size does not preclude herbivory. The herbivores had the highest gut:fish length ratio, which may facilitate plant digestion. While diet did not change seasonally, the mean feeding bite rate was significantly lower in winter than summer for four of the study species.     

Ontogeny of feeding behavior and cranial morphology in the whitespotted bambooshark <Emphasis Type="Italic">Chiloscyllium plagiosum</Emphasis>

Morphological and behavioral development of the feeding apparatus over early ontogeny can profoundly affect the ability of an organism to obtain nourishment, ultimately impacting survival. The interplay between morphology and behavior over the first year of life was studied in the whitespotted bambooshark Chiloscyllium plagiosum (Bennett 1830) beginning in March of 2002 using high-speed videography and dissection. Externally measured variables describing cranial growth, and jaw weight, scaled at or near isometry while jaw and hyoid musculature, especially the coracohyoideus, demonstrated considerable hypertrophication. The difference between the volume of the buccal cavity when open and closed scaled with substantial positive allometry while the time to reach maximum jaw and hyoid abduction exhibited weak allometry, resulting in the capacity for more rapid and greater volumetric intake during feeding. In addition, the relative forward motion of the predator during a strike decreased over ontogeny and the feeding modality became more suction-dominated. Kinematic variables exhibited little variability and the primary aspect of food capture that was modulated in response to food type was the forward motion of the predator. An increase in capture success was noted for live, elusive shrimp over ontogeny indicating that morphological and behavioral changes have direct consequences for prey acquisition. Conservation of head shape coupled with a narrow behavioral repertoire is hypothesized to increase prey capture success in the wild over ontogeny as individuals become more proficient in the execution of a single, low-variability, suction-dominated capture behavior.     

Feeding habits of the albacore tuna <Emphasis Type="Italic">Thunnus alalunga</Emphasis> (Perciformes,Scombridae) from central Mediterranean Sea

In order to assess feeding habits and trophic level of this species, we analysed the stomach content of 189 specimens collected monthly in the southern Tyrrhenian Sea (central Mediterranean Sea). The results showed that this species is a pelagic predator focusing on paralepidid fish and, more in detail, on two species such as Paralepis speciosa and Paralepis coregonoides. Among cephalopods, Heteroteuthis dispar was the most abundant prey item in the stomach contents, whereas among crustaceans the hyperidean amphipods Phrosina semilunata and Brachyscelus crusculum were the most representative species. In the present study, the diet of the albacore did not vary significantly throughout the period of study focusing, in the different season of catch, on the same prey species. Not even a size-related diet shift was observed, with a partitioning of the albacore sample into five size groups. Levin’s standardized index showed a low value indicating a limited trophic niche width, with a diet dominated by a limited number of taxa and then a specialist behaviour for this predator. The estimated TROPH value for T. alalunga resulted very similar to that calculated in Mediterranean Sea for other species as well as Xiphias gladius, Thunnus thynnus, Euthynnus alletteratus and Sarda sarda. Then, the albacore tuna can be considered as a top carnivore.     

Resource use by five sympatric parrotfishes in the San Blas Archipelago,Panama

Resource use by five sympatric species of parrotfish was quantified in the San Blas Archipelago of the Republic of Panama from March to August 1987. Detailed observations of parrotfishes on patch reefs and surrounding seagrass beds showed that they partition resources with respect to habitat, food and size, but not time. Although parrotfishes shared resources, the proportions of each resource used differed significantly among species. Scarus iserti (Bloch) scraped filamentous microalgae that grew from eroded coral pavement on lower slopes of patch reefs and in halos, the area of sparse vegetation surrounding reefs. Sparisoma viride (Bonnaterre) foraged on upper slopes of patch reefs where they mostly took bites from dead coral and associated algae. S. aurofrenatum (Cuvier and Valenciennes) had the broadest diet, which consisted mostly of seagrasses and macro- and microalgae that were attached to dead coral on lower reef slopes and in halos. Although S. chrysopterum (Bloch and Schneider) commonly occurred on patch reefs, it primarily foraged in seagrass beds that surround them. S. rubripinne (Cuvier and Valenciennes) was distributed most widely, ranging from seagrass beds to reef crests, where it took bites from seagrasses, dead coral and macroalgae. Juveniles of all species occurred on lower slopes or in halos where they scraped filamentous microalgae from coral pavement. As they matured, parrotfishes moved into other habitats changing access to different types of food. All of these parrotfishes fed throughout the daytime, and resource use did not differ between morning and afternoon.     

Winter mortality, growth, and behavior of young-of-the-year of four coastal fishes in New Jersey (USA) waters

Winter mortality has been hypothesized to select for large body size in young-of-the-year (YOY) fishes, yet substantiation of winter mortality and its cause(s) are available for few estuarine or marine species. We examined seasonal length distributions of wild populations of four common marine species, black sea bass (Centropristis striata), tautog (Tautoga onitis), cunner (Tautogolabrus adspersus), and smallmouth flounder (Etropus microstomus), and mortality (i.e., frequency of death), growth, and behavior of their YOY in the laboratory at ambient winter temperatures (mean 7°C, range 2-13°C) during a 135-day period (December 1992 through mid-April 1993) to establish potential causes of their mortality in the field. Young-of-the-year black sea bass experienced 100% mortality when water temperatures decreased to 2-3°C in February, emphasizing the importance of winter emigration from estuaries in this southern species. The low mortality of two labrid species, YOY tautog (14%) and YOY cunner (3%), was consistent with their northern distribution and year-round occurrence in estuarine and nearshore coastal waters. Laboratory mortality of YOY smallmouth flounder (33%) was higher for small (<35 mm total length) fish, suggesting that this small species may experience high winter mortality in estuaries and nearshore coastal waters. Seasonal differences in fish length result potentially from several mechanisms (e.g., mortality and/or migration) that are difficult to assess, but our laboratory experiments suggest that seasonal temperature changes cause size-specific mortality of YOY smallmouth flounder and offshore migration of YOY black sea bass.     

Bioerosion of coral reefs by two Hawaiian parrotfishes: species, size differences and fishery implications

Parrotfishes can be significant bioeroders and sediment producers on coral reefs. We quantified the bioerosion rates of two similarly sized Hawaiian parrotfishes with two different feeding modes (Scarus rubroviolaceus—a scraper and Chlorurus perspicillatus—an excavator). The results showed that feeding modes did not affect bioerosion rates but that bioerosion rates were size dependent, with largest individuals (S. rubroviolaceus 45–54 cm FL) bioeroding up to 380 ± 67 kg ind⁻¹ year⁻¹. The size for onset of bioerosion capabilities for both species was 15 cm. Grazing by the two species consumed 60% of the carbonate production of the fore reef area, suggesting that large parrotfishes in Hawaii are ecologically important bioeroders. As individual large S. rubroviolaceus contributed disproportionately more to bioerosion and sediment production than the equivalent biomass of smaller conspecifics, management strategies designed to retain normal reef bioerosion rates should seek to preserve the historical size structure of S. rubroviolaceus populations and to especially protect the larger size classes.     

Impact of epibenthic predation on estuarine intertidal harpacticoid copepod populations

The extent to which energy is transferred directly from benthic meiofauna to epibenthic predators was investigated on an intertidal sand-flat in the Exe estuary, southwest England, during 1981–1982 and compared with data obtained from an intertidal mud-flat in the Lyhner estuary, also in south-west England, between 1978 and 1981. Two species of flatfish (Pleuronectes platessa L. and Platichthys flesus L.), two species of goby [Pomatoschistus microps (Krøyer) and P. minutus (Pallas)], brown shrimp (Crangon crangon L.) and shore crabs (Carcinus maenas L.) are the most common epibenthic predators feeding on the benthic invertebrates in these locatites. Harpacticoid copepods are the only component of the meiofauna to form a significant part of the diet of early juvenile stages of these predators, particularly the invertebrates. Harpacticoids are a more important source of food for predators feeding over the sand-flat than for those feeding on the mud-flat because in the sand-flat alternative prey of suitable size, such as small annelids, are absent. Moreover, the impact of predation on the mud-flat is spread over the whole harpacticoid species spectrum whereas on the sandflat it is confined almost entirely to a single species, Asellopsis intermedia (T. Scott). Flatfish, gobies and shrimp consume daily an estimated 0.01 to 0.1% of the standing stock of A. intermedia and account for between 12 and 22% of the observed reduction in the population of this species between July and October. Therefore, only a very small proportion of total meiofauna biomass is transferred directly to higher trophic levels.     

Growth and production of Sterechinus neumayeri (Echinoidea: Echinodermata) in McMurdo Sound,Antarctica

Population dynamics of Sterechinus neumayeri were investigated at four sites in McMurdo Sound: Cape Evans, McMurdo Station, East Cape Armitage and New Harbor. The annual formation of natural growth bands in the jaws of the Aristotle's lantern was verified by a tagging-recapture experiment. Growth functions based on natural growth bands indicated differences among stations but showed S. neumayeri to be a slow growing species, reaching its maximum diameter of 70 mm at an age of about 40 yr. Annual production ranged between 2.4 (C. Evans) and 0.65 g ash free dry mass m^-2 (New Harbor) and was related to differences in food conditions. More than 95% of total production was invested in reproduction, and less than 5% was invested in somatic growth. Consumption estimates for S. neumayeri showed this species to play a significant role in the benthic trophic web of McMurdo Sound.