Tautogolabrus Research Articles

Behavioural responses of competent lobster postlarvae to odor plumes

We determined the ability of competent laboratory-reared Homarus americanus postlarvae to use odor plumes as a potential mechanism of orientation during the habitat selection process at settlement. In a Y-maze apparatus, both swimming direction (upstream or downstream) and arm selection (control or experimental) were strongly influenced by the nature of the chemical stimulus tested. In control conditions (unconditioned water in both proximal arms of the experimental device), postlarvae swam predominantly upstream (61:39) but displayed no arm preference (48:52). When submitted to a metabolite solution of adult conspecifics or macroalgae, postlarvae swam consistently upstream (≥73%) and showed a significant preference for the arm providing these stimuli (≥69%). In contrast, postlarvae submitted to cunner (Tautogolabrus adspersus) metabolites swam predominantly downstream (68:32), and those that did swim upstream significantly avoided the experimental arm (30:70). In repeated trials with the same individuals, postlarvae behaved similarly in ≥80% of the assays, suggesting a low intra-individual variability in behavioural responses. It is concluded that distance chemoreception may play a role in habitat selection by lobster postlarvae at settlement.

Habitat structure, conspecific presence and spatial variation in the recruitment of a temperate reef fish.

Pronounced spatial variation in recruitment occurs in many marine invertebrate and fish populations and is thought to be critical to the demography of these species. In this study I examined the importance of habitat structure and the presence of conspecific residents to spatial variation in larval settlement and recruitment in a temperate fish Tautogolabrus adspersus. I define settlement as the movement of individuals from the water column to the benthic habitat, while I refer to recruitment as numbers of individuals surviving some arbitrary period of time after settlement. Experiments in which standard habitats were stocked with conspecifics showed that resident conspecifics were not an important factor contributing to small-scale variability in recruitment. Further correlative analyses demonstrated that large-scale variation in recruitment could not be explained by variability in older age classes. By contrast, manipulations of macroalgal structure within a kelp bed demonstrated that recruitment was significantly higher in habitats with a dense understory of foliose and filamentous algae than in habitats with only crustose algae. Understory algae varied in their pattern of disperison among sites, and the dispersion of fish matched that of the plants. In order to determine the effects of differences in patterns of algal dispersion on the demography of associated T. adspersus populations, I used experimental habitat units to manipulate patterns of dispersion. Settlement was significantly greater to randomly placed versus clumped habitats; however, no differences in recruitment between random and clumped habitats were detected. Because recruitment is a function of the numbers of settlers minus the subsequent loss of settlers, rates of mortality or migration must have been higher in the randomly placed habitats. These results are counter to the current paradigm for reef fishes which suggests that larval settlement is the crucial demographic process producing variability in population abundance. In this experiment patterns of settlement were modified by varying the patch structure of the habitat.

Regional variation in fish predation intensity: a historical perspective in the Gulf of Maine.

Regional variation in the intensity of fish predation on tethered brittle stars and crabs was measured at 30-33 m depths in the rocky subtidal zone at seven sites representing coastal and offshore regions of the Gulf of Maine, USA. Analysis of covariance comparing the slopes of brittle star survivorship curves followed by multiple comparisons tests revealed five groupings of sites, with significantly greater predation rates in the two offshore than in the three coastal groups. Brittle stars tethered at the three offshore sites were consumed primarily by cod, Gadus morhua, with 60-100% prey mortality occuring in 2.5 h. In striking contrast, only 6-28% of brittle star prey was consumed in the same amount of time at the four coastal sites, which were dominated by cunner, Tautogolabrus adspersus. In several coastal trials, a majority of brittle star prey remained after 24 h. The pattern of higher predation offshore held for rock crabs as well with only 2.7% of tethered crabs consumed (n=36) at coastal sites versus 57.8% of crabs (n=64) consumed at offshore sites. Another important predatory fish, the wolffish, Anarhichas lupus, consumed more tethered crabs than brittle stars. Videos and time-lapse movies indicated that cod and wolffish were significantly more abundant at offshore than at coastal sites. Three hundred years of fishing pressure in New England has severely depleted stocks of at least one important benthic predator, the cod, in coastal waters. We speculate that this human-induced predator removal has lowered predation pressure on crabs and other large mobile epibenthos in deep coastal communities. Transect data indicate that coastal sites with few cod support significantly higher densities of crabs than offshore sites with abundant cod.

Feeding ecology of benthic mobile predators: experimental analyses of their influence in rocky subtidal communities of the Gulf of Maine

The feeding ecology of mobile predators and their impact on benthic organisms inhabiting the rocky shallow subtidal zone off the coast of Maine, USA, was investigated. To determine diets and degree of prey selection we analyzed gut contents of lobsters ( Homarus americanus Milne-Edwards), two species of crabs ( Cancer irroratus Say and C. borealis Stimpson) and 13 fish species of which pollock ( Pollachius virens (Linnaeus)), cunners ( Tautogolabrus adspersus (Walbaum)), and sculpins (several species) were the most conspicuous species of this assemblage. Dietary data were compared with those on benthic prey availability. In the laboratory, we conducted experiments to test whether there is prey selection in relation to their energetic value. In the field, we conducted two experiments: (1) to test whether fish predators move into the intertidal zone during high tide for feeding purposes; and (2) to test the impact of increased predator abundance in these communities using artificial reefs made of concrete blocks. Large fish and crustacean predators foraged both benthic (mainly invertebrates) and pelagic (mostly fishes) prey. Juveniles or small individuals of crustaceans, mollusks and fish were the most heavily preyed, crabs ( Cancer spp.), mussels ( Mytilus edulis Linnaeus), and herring ( Clupea harengus Linnaeus) being the most common items. Juvenile sea urchins ( Stronglocentrotus droebachiensis (Muller)) were important prey of cunners. In the laboratory, lobsters, cunners and sculpins exhibited strong preference for small crabs and mussels but not for echinoderms. These results were consistent with those obtained with a prey selection index, and were closely related to the energy value of prey, suggesting that these predators behave as energy maximizers. 13 pollock and four cunners were caught in the mid-intertidal zone. These specimens contained a variety of undigested benthic intertidal organisms indicating that they utilize intertidal zones as feeding grounds. These results suggest that fishes may play an important role on the structure and organization of intertidal sessile communities. A significant number of predators colonized the artificial reefs, indicating that the availability of living space is an important factor affecting the distribution and abundance of large mobile predators. These predators reduced the abundance of juvenile or small benthic species, particularly of green sea urchins, in the area surrounding the reefs, suggesting that size-selective predation is presumably the mechanism by which predators influence the structure and organization of benthic communities in these environments.

Effects of microhabitat on recruitment variation in a Gulf of Maine reef fish

Variation in recruitment of larvae can be important in determining temporal and spatial variat~on in adult demersal fish populations. Thls study examines how microhabitat use by newly settled cunner Tautogolabrus adspersus (Pisces. Labrldae) influences small-scale recruitment variation. The microhabitat occupied by cunner recruits was characterized by quantifying 14 attributes of the microhab~tat at 2 sites in Southern Malne, USA. Attributes at randomly selected sites were also recorded. Cunner recruits were distributed nonrandomly anlong microhabitats wlthin sltes. Recruit presence was positively associated with the presence of macrophytes and negabvely associated with microhabitats of low structural complexity. Association with specific microhabitats differed among sites; however, microhabitats available also differed among sites. While presence or absence could be prebcted by attributes of microhabitats, small-scale densities of fish could not. These data suggest that microhabitat use is nonrandom, and that the distribution of microhabitat types may influence small scale spatial patterns of recruitment in this species.

Thermal hysteresis activity in the skin of the cunner, Tautogolabrus adspersus

Previous studies have shown that cunners, Tautogolabrus adspersus, remain inshore in marine waters around Newfoundland during the winter months, but are in a state of metabolic torpor, apparently surviving by undercooling without freezing. The present study reports the discovery of measurable levels of thermal hysteresis activity in aqueous extracts of winter cunner skin, but not in the blood plasma. The occurrence of a compound with thermal hysteresis activity indicates the presence of antifreeze polypeptides in the Labridae. This is of significant interest, since this family is mostly tropical in distribution, and has likely invaded northern waters in relatively recent times. The functional significance of skin thermal hysteresis activity is discussed in relation to the protective role of antifreeze compounds.

Assessment of the potential for mixed-function oxygenase enzyme induction in the extrahepatic tissues of cunners ( tautogolabrus adspersus) during reproduction

One of the primary interests which have developed in aquatic toxicology over the past few years has been the use of the induction of mixed-function oxygenase (MFO) enzymes as a sensitive biochemical indicator for use in biological monitoring and assessment studies. Over 30 field trials had been reported to 1987 with fish indicating that induction may be common at various sites in the environment worldwide. 1 – 3 A number of other field trials have also been reported within the last two years. Most studies have focused on induction in liver but evidence suggests that liver tissues may be refractory to induction during reproduction. 4 We have investigated the potential for induction in extrahepatic and hepatic tissues of cunners pulsed with No. 2 fuel oil at various stages of reproduction. Both male and female fish were exposed during prespawning, early spawning and late spawning and induction was readily resolved in all tissues of both sexes during the three stages. The results on extrahepatic induction potential are of general toxicological interest and will find application in the design of future field studies.

Summer ichthyoplankton communities of two estuarine systems of Prince Edward Island

Fish eggs and (or) larvae representing 22 species in 14 families were collected during the summer of 1983 at eight stations in the Hillsborough River estuary – Northumberland Strait area and three stations in the Tracadie Bay – Gulf of St. Lawrence region. Of the 62 287 eggs collected, 83.5% were either yellowtail flounder, Limanda ferruginea, or cunner, Tautogolabrus adspersus, and 5.9% were Atlantic mackerel, Scomber scombrus. The most abundant larvae were alewife, Alosa pseudoharengus, Atlantic mackerel, and cunner accounting for 24.6, 22.4, and 20.6%, respectively, of the total 5077 larvae and juveniles collected. The highest average concentration of eggs and larvae occurred in the coastal area near Tracadie Bay (4265 eggs/100 m3, 350 larvae/100 m3), in the Northumberland Strait region (2682 eggs/100 m3), and at the head of the Hillsborough River system (170 larvae/100 m3). The greatest species diversity occurred near Tracadie Bay (5.0 species of larval fish per tow) and in Tracadie Bay channel (4.0 species of larval fish, 6.0 species of eggs per tow). Summer variations in abundance and distribution were correlated with water temperature and salinity for the more abundant species (alewife, cunner, Atlantic mackerel, Gasterosteus aculeatus, Morone americana, Osmerus mordax, Menidia menidia, Pseudopleuronectes americanus). Species associations and station assemblages were analyzed using the Bray – Curtis dissimilarity measure and a numerical classification system.

Predation upon postlarval lobsters Homarus americanus by cunners Tautogolabrus adspersus and mud crabs Neopanope sayi on three different substrates: eelgrass, mud and rocks

Predation upon postlarval lobsters Homarus americanus by cunners Tautogolabrus adspersus and mud crabs Neopanope sayi on three different substrates: eelgrass, mud and rocks

Differential Spawning Success among Territorial Male Cunners, Tautogolabrus adspersus (Labridae)

Field observations of the cunner, Tautogolabrus adspersus (Walbaum), showed that the frequency of spawnings was significantly different between territorial males. There were significant positive correlations between spawning frequency and both courtship frequency and territory size, but not between spawning frequency and depth of territory, male size, or density of various food items in territories. Our analyses of relations between traits of males and of their territories and spawning frequency indicate that male characteristics are better predictors of spawning success (in terms of frequency of observed spawns) than the characteristics of their territories. However, the primary function of male territoriality also seems to be related to reproduction.

An experimental investigation of juvenile lobster habitat preference and mortality among habitats of varying structural complexity

Juvenile lobsters Homarus americanus H. Milne-Edwards, stages IV and V, were tested experimentally and found to choose habitats with seaweed (Irish moss Chondrus crispus Stackhouse) more frequently than habitats without. In still water the ratio was 70:30 and in moderate currents of 0.1–0.3 m · s −1 it was 75 : 25 or 3 to 1. Lobster habitat preferences in these experiments may be explained by possible biochemical cues from the living algae, light avoidance responses, thigmotactic responses, and by clearly seeking shelter from the water currents. When fish predators (cunner Tautogolabrus adspersus Walbaum) were introduced, the lobsters responded by standing still, or backing away, thus increasing the time taken to reach cover by a factor of almost 5. In the presence of two cunners for 24 h, the mortality of lobsters was 97% on a plain sand bottom, 85% on sand with five perforated bricks, but only 69% in a habitat with bricks covered with seaweed. It is concluded that seaweeds and habitat complexity have a positive influence on habitat selection by juvenile lobsters and that they reduce lobster mortality.

Paradoxical effects of cadmium exposure on antibacterial antibody responses in two fish species: Inhibition in cunners ( Tautogolabrus adspersus) and enhancement in striped bass ( Morone saxatilis)

Previous work in a marine fish, the cunner ( Tautogolabrus adspersus), showed that endocytosis of bacteria by cells in the liver and spleen was affected by 96-h exposure of the fish to cadmium at a concentration of 12 μg/mρ; however, antibody response to sheep erythrocytes was not affected. Since the latter finding was questionable because of short immunization times, and data from more than a single fish species were desirable, both the cunner and an anadromous fish, the striped bass ( Morone saxatilis), were examined for antibody responses against the bacterium Bacillus cereus in Freund's complete adjuvant during a 6- to 8-wk time period. Exposure to 12 μg/mρ cadmium caused significant inhibition of serum antibody titers (P<0.007) in cunners. Paradoxically, antibody response in striped bass exposed to 10 μg/mρ cadmium was enhanced sixfold. This enhancement was weaker but still evident when the antigen was injected 48 d after cadmium exposure. Peritoneal exudate cells from cadmium-exposed striped bass also showed more active migration through microporous filters than cells from non-exposed fish. Since the 96-h cadmium LC 50 was 26 μg/mρ for cunners and 20 μg/mρ for striped bass, the differences in antibody response could not be explained on the basis of differences in cadmium toxicity. Although geometric mean liver cadmium levels after exposure at 15°C were higher in cunners (163.8 ± 1.2μg/gm) than in striped bass (64.4 ± 1.2μg/g), cunners exposed to cadmium at 2°C had lower cadmium levels (46.4 ± 1.2μg/g) which were still effective in inhibiting antibody production at 8°C. On the other hand, striped bass not exposed to cadmium showed a strong, exponential rise in serum antibody when the temperature at immunization, 14°C, was reduced to 9°C; whereas cunners held in the same tanks exhibited a weaker, biphasic serum antibody response. Regardless of the cause (innate differences in cellular response, or better stress adaptability in an anadromous fish), the data show that chemical-stress effects on the immune system of one fish species cannot be extrapolated to another species.

Courtship, spawning, and parental care behavior of the lumpfish, Cyclopterus lumpus L., in Newfoundland

The courtship, spawning, and paternal care behavior of lumpfish, Cyclopterus lumpus, in Broad Cove, Newfoundland, are described. Breeding lumpfish are sexually dimorphic and exhibit a distinct sexual dichromatism during reproduction. Spawning females are larger than males and pale blueish green in color. Male lumpfish nuptial coloration consists of a greyish black body and an orange–red ventral surface and fins. Spawning follows an extended courtship involving nest cleaning, fin brushing, and quivering. Females extrude pink eggs onto the surface of the nest which the male fertilizes. After fertilization, males mold the eggs into the nest, producing funnel-like depressions in the egg mass. Males remain with the eggs throughout the incubation period providing parental care. Pectoral fanning and puffing, the expelling of water from the mouth towards the surface of the egg mass, are the predominant parental care behaviors exhibited throughout the incubation period. Quantitative variation between males in the amount of time spent in parental care was independent of male size. Egg masses are maintained free of invertebrate predators by the male, but males are unable to defend eggs against predation by large groups of cunners, Tautogolabrus adspersus. Puffing behavior was more frequent towards the end of the incubation period than at the beginning. During hatching emergent larvae are swept from the nest site by male fanning and puffing behaviors.

The importance of plant defence abilities to the structure of subtidal seaweed communities: The kelp Laminaria longicruris de la Pylaie survives grazing by the snail Lacuna vincta (Montagu) at high population densities

Following mass mortalities of sea urchins, Strongylocentrotus droebachiensis (Müller), in the rocky subtidal of the Atlantic coast of Nova Scotia, dense seaweed beds dominated by the canopy-forming kelp Laminaria longicruris de la Pylaie developed for the first time in several years. The numerically abundant grazers in the seaweed beds when sea urchins were rare were the mesogastropod Lacuna vincta (Montagu), the limpet Notoacmaea testudinalis (Müller), and the chiton Tonicella rubra (Linné). The limpet and chiton are unable to graze the macroscopic sporophytes of Laminaria, and a manipulation experiment showed that they have no significant effect on the recruitment of this kelp. In contrast, Lacuna grazes the macroscopic sporophyte and several of its population characteristics suggested that it might be a potentially important grazer of Laminaria. Snails can occur in high densities and several invasions of an area may occur during a single season; they manifest strong preference for Laminaria in the subtidal region; post-metamorphic individuals have considerable ability for dispersal; and predation by their principal predator, the labrid fish Tautogolabrus adspersus (Walbaum) is limited in time and space. Despite this potential, the estimated direct consumption of kelp laminae by snails was negligible, amounting to only ≈ 0.05 % of the total blade biomass (fresh wt) that was available during their season. However, the snails′ overall impact on the Laminaria canopy was significant. Because grazing was concentrated on the frilled margins of laminae, and the holdfast, stipe and intercalary meristem were largely avoided, grazing promoted the tearing away of the margins of blades, resulting in a significant reduction in canopy area without increasing kelp mortality. Since there was no grazer-induced mortality of Laminaria, the canopy was closed following the growth burst of the kelps early in the spring, and there was little opportunity for understorey species to benefit from the temporarily high light levels. If the distribution of grazing by the snails had been more uniform and caused significant mortality of Laminaria, major changes in the structure of the seaweed assemblage would have occurred. We suggest that the pattern of Lacuna grazing on Laminaria is governed by the distribution of anti-herbivore chemicals in the plants, and variations in the toughness and nutritional quality of different regions of the plant. Avoidance of the intercalary meristem correlates with high levels of polyphenols in this area. Polyphenol concentration is uniformly low throughout the rest of the plant. The distribution of snail grazing on the stipe and holdfast, and central and lateral portions of the lamina correlates with the toughness and nutritional quality of these parts. The nature of the anti-herbivore defences of Laminaria, which are effective against grazing by Lacuna but not by the urchins, indicates a trade-off between high specific growth rates and reproductive output (and thus superior competitive ability) versus development of defences. This strategy is consistent with cost-effective arguments relating resource allocation and fitness.

Burrows protect postlarval lobsters Homarus americanus from predation by the non-burrowing cunner Tautogolabrus adspersus, but not from the burrowing mud crab Neopanope texani

Burrows protect postlarval lobsters Homarus americanus from predation by the non-burrowing cunner Tautogolabrus adspersus, but not from the burrowing mud crab Neopanope texani

Efficiency of Large-Volume Plankton Pumps, and Evaluation of a Design Suitable for Deployment from Small Boats

A critical review of previously published studies, and evaluation of a newly developed pump system, showed the often stated shortcomings of large-volume pumps as instruments for sampling plankton communities (e.g. damage to organisms sampled, volumes too small to estimate plankton density accurately, and systems too cumbersome to handle) to be invalid. Previously published estimates of the comparative efficiency of large-volume pump samplers and tow nets should; however, be viewed with caution because the techniques used to estimate pumped volume are error prone. In-line flow meters are essential for accurate volume estimation. Comparative efficiency tests of a newly developed large-volume pumping system deployed simultaneously with 80- and 153-μm mesh standard plankton nets revealed that the pump, while sampling only 8% of the volume sampled by the nets, was equally effective in capturing capelin (Mallotus villosus) larvae (5-mm length), herring (Clupea harengus) larvae (9-mm length), large copepods (&gt; 750 μm), small jellyfish, and hyperiid amphipods. The pump was superior to nets in sampling crab zoea and megalops larvae and becomes more efficient at capturing euphausiids and chaetognaths as their natural densities increase. Nets were superior in the capture of fish eggs (primarily cunner, Tautogolabrus adspersus), possibly due to the vertical distribution of eggs in the water column. The average length of capelin larvae captured by pumping was consistently 0.2 mm longer than that of larvae taken in nets, but the length–frequency distribution of larvae sampled was similar to that of larvae entering the pelagic environment. Attaching the pump intake to the cod-end of a rigid tow net is suggested as a method of surmounting potential errors when sampling organisms at densities below 1–5/m3.

Pathology of five species of Gyrodactylus Nordmann, 1832 (Monogenea)

Attachment-site pathology of the ectoparasites Gyrodactylus adspersi Cone and Wiles, 1983 on Tautogolabrus adspersus, Gyrodactylus avalonia Hanek and Threlfall, 1969 on Gasterosteus aculeatus, Gyrodactylus bullatarudis Turnbull, 1956 on Poecilia reticulata, Gyrodactylus sp. on Carassius auratus, and Gyrodactylus salmonis (Yin and Sproston, 1948) on Salmo gairdneri was examined using optical microscopy and scanning electron microscopy. In the first four species, the disc-shaped haptor attached itself to the host skin surface by means of blade tips of 16 peripherally located marginal hooks, with the two ventrally located hamulus blades compressing the underlying epithelium into a small depression. Tissue damage from attachment and feeding was minimal. However, G. salmonis lodged its marginal hook sickles deep into the host epidermis and appeared to cause extensive fin damage and skin discoloration. There was little evidence of bacterial involvement in the wounds, but bacterial microcolonies were observed on the body surface and haptor of G. salmonis. The latter results are discussed in relation to our understanding of gyrodactyliasis.

Comparisons of the feeding activity and diets of male and female cunners Tautogolabrus adspersus (Pisces: Labridae)

The diel distribution of feeding activity during the spawning season was compared for territorial male and female cunners Tautogolabrus adspersus in Conception Bay, Newfoundland, Canada between June and August, 1978. Territorial males feed significantly less often than females and concentrate their feeding activities in the morning, whereas females feed as frequently in the afternoon as in the morning. Based on the contents of alimentary tracts, territorial males, non-territorial males, and females have different diets. Since these three groups share the same habitat, the observed dietary differences probably reflect differences in their foraging behaviour. The relevance of these findings to the concept of ‘time minimizer’ and ‘energy maximizer’ is discussed.

Summer food of the Great and Double-crested Cormorants on the Magdalen Islands, Quebec

This study of the food of the Great Cormorant (Phalacrocorax carbo) and the Double-crested Cormorant (P. auritus) on the Magdalen Islands, Quebec, is based on regurgitations and pellets collected on nesting sites during the summers of 1977 and 1978. Both species generally ate flatfishes (especially the winter flounder, Pseudopleuronectes americanus), American sand lances (Ammodytes americanus) and cunners (Tautogolabrus adspersus). Relatively more Great Cormorants than Double-crested Cormorants ate flatfishes and cunners during both summers, while relatively more Double-crested Cormorants fed on American sand lances during the summer of 1977. These fishes and other prey taken in lesser extent were mostly bottom-associated species; however both cormorants, especially the Double-crested Cormorant, take advantage of Capelin (Mallotus villosus) and Atlantic Herring (Clupea harengus harengus) schools which come spawning close to the seashore. Great and Double-crested cormorants appear to be opportunistic feeders since their diet varies with the availability of prey.

Comparative morphology of Gyrodactylus groenlandicus Levinsen, 1881, G. nainum Hanek and Threlfall, 1970, G. pleuronecti Cone, 1981, and G. adspersi sp. n. (Monogenea) from northwest Atlantic fishes

Gyrodactylus groenlandicus from Myoxocephalus scorpius, G. nainum from Myoxocephalus quadricornis, G. pleuronecti from Pseudopleuronectes americanus, and Gyrodactylus adspersi sp. n. from Tautogolabrus adspersus, collected from the northwest Atlantic Ocean, are compared morphologically. Gyrodactylus groenlandicus has long hamuli (63–66 μm) and long marginal hooklets (35–36 μm). Gyrodactylus nainum and G. pleuronecti have intermediate-sized hamuli (56–58 and 55–59 μm, respectively); the marginal hooklets of G. nainum are 35–36 μm in length while those of G. pleuronecti are 28–29 μm. Gyrodactylus adspersi sp. n. has short hamuli (38–43 μm) and short marginal hooklets (24–27 μm). The four species differ subtly, but distinctly, in morphology of the marginal hooklet sickle. The study concludes with discussion of possible evolutionary relationships between the four species.