Offshore Habitat Preference of Overwintering Juvenile and Adult Black Sea Bass,Centropristis striata,and the Relationship to Year-Class Success

Black sea bass (Centropristis striata) migrations are believed to play a role in overwinter survival and connectivity between juvenile and adult populations. This study investigated oceanographic drivers of winter habitat choice and regional differences between populations of juvenile and adult black sea bass. Trends in cohort strength, as a result of juvenile survival, were also identified. Oceanographic and fisheries survey data were analyzed using generalized additive models. Among the oceanographic variables investigated, salinity was the main driver in habitat selection with an optimal range of 33–35 practical salinity units (PSU) for both juveniles and adults. Preferred temperature ranges varied between juveniles and adults, but held a similar minimum preference of >8°C. Salinity and temperature ranges also differed by regions north and south of Hudson Canyon. Shelf water volume had less of an effect than temperature or salinity, but showed an overall negative relationship with survey catch. The effect of winter conditions on juvenile abundance was also observed across state and federal survey index trends. A lack of correlation observed among surveys in the fall paired with a strong correlation in the spring identifies the winter period as a factor determining year-class strength of new recruits to the population. A rank order analysis of spring indices identified three of the largest year classes occurring during years with reduced shelf water volumes, warmer winter shelf waters, and a 34 PSU isohaline aligned farther inshore. While greater catches of black sea bass in the northwest Atlantic Ocean remain south of Hudson Canyon, the species’ range has expanded north in recent years.     

Social Play among Juvenile Bighorn Sheep: Structure,Development, and Relationship to Adult Behavior

A 27-mo study of bighorn sheep (Ovis canadensis) was conducted to examine the structure and development of social play among lambs, and to compare that behavior with the behavior of yearlings and adults. Male lambs played more than females and exhibited a larger repertoire. The behavior patterns used by lambs in social play were the same as those used by adults in intrasexual conflict and courtship. However, the repertoire of lambs was more limited than that of adults. Lambs chose partners closest in age to interact with, regardless of sex. Results were consistent with the hypothesis that play serves to develop physical skills and strength.     

Reduction of Reactive Distance and Foraging Success in Smallmouth Bass, Micropterus dolomieu, Exposed to Elevated Turbidity Levels

We determined how turbidity affected the reactive distance and foraging success of smallmouth bass, Micropterus dolomieu. Smallmouth bass reactive distance decreased exponentially with increasing turbidity, from 65cm in clear water to 10cm at the highest turbidity. Turbidity significantly decreased the probability of a fish reacting to a prey item, but did not influence foraging success following reaction to the prey. Elevated turbidity may reduce stream fish foraging efficiency and decrease prey consumption.     

Habitat Preference, Reproduction and Diet of the Earthworm Eel, Chendol keelini (Teleostei: Chaudhuriidae)

The ecology of the earthworm eel, Chendol keelini, was studied in the field over a period of nine months. In addition this information was supplemented by aquarium observations. The species was most abundant in pools where it was associated with leaf litter and mats of fine tree roots along the banks. It fed on benthic invertebrates, especially chironomid and ephemeropteran larvae. C. keelini is sexually dimorphic; adult males develop a headhump and grow to a larger size than females. Reproduction was seasonal; the reproductive phase coincided with the wet season and lasted for several months. Fecundity was around 40 eggs per clutch. The eggs were spherical, between 1.2 and 1.5mm in diameter, and possessed a pair of long filaments for adhesion to the substrate. Females probably spawned more than once during the breeding season. The length frequency distributions and juvenile growth suggest that C. keelini is a short-lived species that matures during the first year with few individuals surviving to the second breeding season.     

The Red Riviera: Gender, Tourism, and Postsocialism on the Black Sea

The Red Riviera: Gender, Tourism, and Postsocialism on the Black Sea . Kristen Ghodsee. Durham, NC: Duke University Press, 2005. 226 pp.     

Species Composition and Habitat Preference of Watermolds in the Nainital District of Kumaun Himalaya,India

A total of thirty two species of watermolds have been identified from the entire study area. Of these, 22 % species were restricted to water, 44 % to soil and 34 % occurred in water and soil both. The maximum number of species were found during rainy season in both the ecosystems. Pythium s pp. were dominant in terrestrial ecosystem whereas Pythium s pp. and Saprolegnia spp. were dominant in water system. There were two clusters indicative of presence of two distinct communities in both the systems.     

The Acclimation of European Sea Bass (Dicentrarchus labrax) to Temperature: Behavioural and Neurochemical Responses

Studies on fish behavioural and neurophysiological responses to water temperature change may contribute to an improved understanding of the ecological consequences of global warming. We investigated behavioural and neurochemical responses to water temperature in European sea bass (Dicentrarchus labrax) acclimated to three temperatures (18, 22 and 28°C). After 21 d of acclimation, three groups of 25 fish each were exposed to four behavioural challenges (foraging, olfactory, aversive and mirror tests). The expression of choline acetyltransferase (ChAT) was then analysed by Western blotting in CNS homogenates (from a subset of the same fish) as a marker for cholinergic system activity. In both foraging and olfactory tests, fish acclimated to 28°C exhibited significantly higher arousal responses than fish acclimated to lower temperatures. All specimens showed fright behaviour in the aversive test, but the latency of the escape response was significantly less in the fish at 28°C. Finally, the highest mirror responsiveness was exhibited by the fish acclimated to 22°C. As in the case of cholinergic neurotransmission, significantly higher ChAT levels were detected in the telencephalon, diencephalon, cerebellum and spinal cord of fish acclimated to 22 or 28°C in comparison with those maintained at 18°C. Lower ChAT levels were detected in the mesencephalon (optic tectum) at 22 and 28°C than at 18°C. These data indicate that neuronal functions are affected by water temperature. Increases or decreases in ChAT expression can be related to the functional modulation of brain and spinal cord centres involved in behavioural responses to temperature change. Overall, the results of this study suggest that the environmental temperature level influences behaviour and CNS neurochemistry in the European sea bass.     

The Relationship Between Habitat Selection and Preference for Adult and Larval Food Resources in the Polyphagous Butterfly <Emphasis Type="Italic">Vanessa cardui</Emphasis> (Lepidoptera: Nymphalidae)

Search strategies can have profound fitness-effects for plant-feeding insects. Here I focus on the potential conflict between searching for nectar plants and for larval food plants. I test if the butterfly Vanessa cardui, which can use some of its larval food plants as nectar sources, is able to rationalize this search problem by combining the two search tasks. Lab-experiments revealed a higher oviposition preference for Cirsium arvense over Urtica dioica and a corresponding difference in larval performance. Contrary to predictions, there was no effect of inflorescences on oviposition. However, experiments in large outdoor cages showed a higher occupancy and a higher level of oviposition in patches with access to nectar sources, even on U. dioica. Hence, while there was no preference for individual plants with flowers, the results suggests that V. cardui is simplifying its search task to primarily search for hosts in nectar-rich patches. This strategy allows females to increase oviposition rate, but it is likely that it comes at the expense of not always using optimal host plants in terms of offspring performance.     

Embryonic,Larval, and Juvenile Development of the Sea Biscuit Clypeaster subdepressus (Echinodermata: Clypeasteroida)

Sea biscuits and sand dollars diverged from other irregular echinoids approximately 55 million years ago and rapidly dispersed to oceans worldwide. A series of morphological changes were associated with the occupation of sand beds such as flattening of the body, shortening of primary spines, multiplication of podia, and retention of the lantern of Aristotle into adulthood. To investigate the developmental basis of such morphological changes we documented the ontogeny of Clypeaster subdepressus. We obtained gametes from adult specimens by KCl injection and raised the embryos at 26C. Ciliated blastulae hatched 7.5 h after sperm entry. During gastrulation the archenteron elongated continuously while ectodermal red-pigmented cells migrated synchronously to the apical plate. Pluteus larvae began to feed in 3 d and were 20 d old at metamorphosis; starved larvae died 17 d after fertilization. Postlarval juveniles had neither mouth nor anus nor plates on the aboral side, except for the remnants of larval spicules, but their bilateral symmetry became evident after the resorption of larval tissues. Ossicles of the lantern were present and organized in 5 groups. Each group had 1 tooth, 2 demipyramids, and 2 epiphyses with a rotula in between. Early appendages consisted of 15 spines, 15 podia (2 types), and 5 sphaeridia. Podial types were distributed in accordance to Lovén''s rule and the first podium of each ambulacrum was not encircled by the skeleton. Seven days after metamorphosis juveniles began to feed by rasping sand grains with the lantern. Juveniles survived in laboratory cultures for 9 months and died with wide, a single open sphaeridium per ambulacrum, aboral anus, and no differentiated food grooves or petaloids. Tracking the morphogenesis of early juveniles is a necessary step to elucidate the developmental mechanisms of echinoid growth and important groundwork to clarify homologies between irregular urchins.     

Age-Specific Behavior and Habitat Selection of Adult Male Damselflies, Calopteryx maculata (Odonata: Calopterygidae)

We compared the age, movement, and time–activity budgets of male Calopteryx maculata damselflies occupying off-stream tree-fall gaps with those at stream sites within a 10-ha woodland. All males collected at off-stream sites were younger than males collected at stream sites—as indicated by their significantly higher wing transmittance. Thirty-three percent of teneral males marked at off-stream gaps moved to stream sites within 4 days (mean distance = 140 m), while mature males marked at stream sites never left the stream. In contrast to stream site males, off-stream males spent significantly more time capturing prey and never engaged in aggressive interactions with other males. Behavioral differences were not due to variations in the operative body temperature. However, malaise trapping revealed a greater frequency of suitable prey in forest light gaps. Our findings support the idea that teneral male Calopteryx leave their emergence sites along the stream for off-stream light gaps to forage without interference and build the energy reserves necessary to attain and hold streamside territories.