Studies on the content and nature of the phycocolloid from Corynomorpha prismatica (Rhodophyta,Cryptonemiales)

The phycocolloid from the red seaweed Corynomorpha prismatica J. Agardh (Cryptonemiales, Crateloupiaceae) has been investigated and found to show positive optical rotation ([] _D ²⁵ + 83^o), to be soluble in potassium chloride solution, to have a total sulphate content of 18.6±1.2% in unmodified gel and 15.0±0.9% in gel modified with lime. Total phycocolloid yields of 17.6±1.6% and 32.2±3.0% were obtained in gel extraction without lime and with lime added, respectively. The infrared spectra of the phycocolloid showed a broad absorption band at 860 to 800 cm^-1 and lacked single sharp peaks at 805 cm^-1. The phycocolloid was concluded to be a carrageenan akin to the lambda-type.     

Scaling relationships,individual variation and the influence of temperature on maximum swimming speed in early settled stages of the turbot Scophthalmus maximus

Escape-swimming speeds (U _max) were studied in settled turbot (Scophthalmus maximus L.) reared at 18°C. Metamorphosis was complete at 4.0 cm total length (TL). U _max scaled in proportion to TL^0.74 in fish of 0.88 5o 8.00 cm TL at 18C. The scaling relationship for U _max was similar for temperatures between 13 and 23°C and could be fitted by the model: . U _max temperature-dependent, with a Q₁₀ of 1.77 over the temperature range studied. Analysis of covariance showed that U _max for farmed turbot was 14% lower than for wild fish filmed within 2 wk of capture; 3 mo after capture the average differences in escape performance were no longer significant, which suggests that the lower escape speeds of farmed fish are due to acclimation effects and not genetic stock differences. In order to assess the individual variability of U _max, 18 wild juvenile turbot [TL=6.2±0.4 cm (Week 1) to 7.5±0.5 cm (Week 17); means±SD] were maintained in individual containers at 18°C. U _max was determined weekly for 6 wk, standardised for fish length using the scaling relationship U _max=1.46 TL ^0.74, and individuals were ranked in order of performance. Temperature was reduced after 6 wk to 13°C, resulting in a significant decline in U _max from 104.0±14.4 to 87.8±12.5 cm s^-1 (means±SD). After 3 wk at 13°C U _max had increased to a level not significantly different from that at 18°C. Kendall's coefficient of concordance showed that repeatability of ranking of the experimental U _max of individuals was maintained over a 13 wk period and through temperature change. The results demonstrate that escape-swimming speeds in juvenile turbot are repeatable, individually variable, and can be modified in response to temperature acclination.     

Habitat use,urea production and spawning in the gulf toadfish <Emphasis Type="Italic">Opsanus beta</Emphasis>

Field studies were conducted in Johnson Key Basin, Florida Bay, USA from September 2002 through September 2004 to examine physiological, ecological, and behavioral characteristics of the gulf toadfish, Opsanus beta (Goode and Bean in Proc US Natl Mes 3:333–345, 1880), in relation to nitrogen metabolism, habitat usage, and spawning. Fish collected 5 cm above sediments in experimental shelters (epibenthic) were compared with those collected by throw traps which were found on or burrowing within sediments. The relationship between microhabitat ammonia and urea excretion, as determined by the enzymatic activity of glutamine synthetase (GS), was examined. The hypothesis tested was that O. beta occupying epibenthic nests were less ureotelic with lower GS activities than non-nesting individuals on/in sediments, due to a decreased environmental ammonia burden. Porewater total ammonia (T _Amm) concentrations at a sediment depth of 5 cm, i.e., the approximate depth of burrowing toadfish, ranged from 0 to 106.5 μmol N l⁻¹ while the pH ranged from 7.48 to 9.14. There was a weak but significant correlation between environmental ammonia (NH₃) concentration and hepatic GS activity for epibenthic toadfish (P < 0.001, r ² = 0.10), but not for burrowing toadfish. Mean urea-N and T _Amm concentrations within shelters occupied by toadfish (n = 281) were 9.8 ± 0.83 μmol N l⁻¹ and 13.0 ± 0.7 μmol N l⁻¹, respectively. As predicted, hepatic GS activity was significantly lower in epibenthic toadfish captured in shelters (4.40 ± 0.24 μmol min⁻¹ g⁻¹; n = 281) as compared to individuals on/in sediments (6.61 ± 0.47 μmol min⁻¹ g⁻¹; n = 128). Glutamine synthetase activity generally peaked in March (spawning season) and was lowest in July. Gender differences in hepatic and branchial GS activity were also found during the spawning season, which is attributable to the fact that males brood and guard offspring in their epibenthic nests while females often rest on or burrow into the sediments. Finally, hepatic and branchial GS appeared to have different patterns of enzymatic activity suggesting functional differences in gene expression.     

Day-night differences in the emergence of demersal zooplankton from a sand substrate in a kelp forest

Day-night differences in abundance and biomass of demersal zooplankton in the water column were determined by trapping these animals as they emerged from the sand substrate in a kelp forest (Macrocystis pyrifera) ecosystem off Santa Catalina Island, California, USA. The day and night sampling periods of the 24 June 1979 new moon each lasted 12 h. Abundance and biomass of total demersal zooplankton were significantly higher in night samples. A mean of 2,425±1,168 demersal zooplankton m^-2 24 h^-1 migrated over a diel cycle; 97% of these animals were crustaceans. The mean biomass of demersal zooplankton was 94.2±27.6 mg ash-free dry wt m^-2 24 h^-1. No significant differences were found in either the abundance or biomass of demersal zooplanktion collected in low and high traps, suggesting that most animals collected 25 cm off the bottom can sustain swimming to at least 75 cm and that both traps give comparable estimates of the amount of demersal zooplankton available to planktivorous predators.     

Diet and seasonal prey capture rates in the Mediterranean red coral (Corallium rubrum L.)

Gorgonians are passive suspension feeders, contributing significantly to the energy flow of littoral ecosystems. More than in active suspension feeders (such as bivalves, ascidians and sponges) their prey capture is affected by spatial and temporal prey distribution and water movement. Corallium rubrum is a characteristic gorgonian of Mediterranean sublittoral hard bottom communities. This study found a high variability in the annual cycle of prey capture rate, prey size and ingested biomass, compared to other Mediterranean gorgonians. Detrital particulate organic matter (POM) was found throughout the year in the polyp guts and constituted the main proportion of the diet (25–44%). Crustacean fragments and copepods (14–46%) accounted for the second major proportion, while invertebrate eggs (9–15%) and phytoplankton (8–11%) constituted the smallest part of the diet. To verify the importance of detrital POM in the energy input of this precious octocoral species, in situ experiments were carried out during the winter–spring period. The results confirm the importance of detrital POM as the main source of food for C. rubrum [0.13±0.04 μg C polyp⁻¹ h⁻¹ (mean±SD)]. This study also compares the prey capture rates of two colony size classes and two depth strata: Within the same patch, small colonies (<6 cm height) captured significantly more prey per polyp (0.038±0.09 prey polyp⁻¹ h⁻¹) than larger colonies (>10 cm high) (0.026±0.097 prey polyp⁻¹ h⁻¹) and showed a higher proportion of polyps containing prey (17% compared to 10%). Comparing colonies of similar size (<6 cm height) revealed that the colonies situated at 40 m depth captured significantly more prey (0.038±0.09 prey polyp⁻¹ h⁻¹) than the ones at 20 m (0.025±0.11 prey polyp⁻¹ h⁻¹). One pulse of copepods was recorded that constituted 16% of all captured prey during the 15-month period studied in one of the sampled populations. The data suggest that the variability of hydrodynamic processes may have a higher influence on the feeding rate than seasonal changes in the seston composition. The carbon ingestion combined with data on the density of the exploited population results in 0.4–9.6 mg C m⁻² day⁻¹. The grazing impact of current, heavily exploited and small-sized populations is comparable to that of larger Mediterranean gorgonians, suggesting that unexploited red coral populations may have a high impact compared with other passive suspension feeders.     

Fission and its effect on population structure of Holothuria atra (Echinodermata: Holothuroidea) in Taiwan

Populations of Holothuria atra Jaeger occurring at Wanlitung and Nanwan were sampled monthly at spring tide from March 1990 to February 1992 in southern Taiwan. At Wanlitung, small individuals with evidence of fission and regeneration were abundant in shallow tidepools on the wide reef flats (density: 98±40 ( ± SD) 100 m^-2, body weight: 6 to 182 g). At Nanwan, large individuals with no evidence of fission were sparse in deep tidepools and narrow flats [density: 0.24±0.07 ( ± SD) 100 m^{- 2}, body weight: 351 to 1400 g]. At Wanlitung, fission occurred throughout the year with an average monthly fission frequency of 4.5%, peaking at 18% in September 1990 and 16% in August 1991. Fission was accomplished by revolving, twisting, and stretching of the body, resulting in two unequal fragments. The minimal weight of 3007 individuals measured during 1 yr at Wanlitung was 6 g. All ten individuals weighing 6 to 9 g ( ± SD = 6.7 ± 1.1) 100 m^{- 2} showed evidence of regeneration from fission products. Nine large individuals (>500 g) transferred from Nanwan to Wanlitung and 50 small individuals (<100 g) transferred from Wanlitung to Nanwan in February 1991 showed no evidence of fission during the following year. Fission occurs in small individuals living in shallow tidepools, suggesting that fission probably is triggered by a stressful environment resulting from solar radiation at the unusually low water level of spring tide. Fission of H. atra at Wanlitung results in a population consisting of small individuals.     

Trophic diversity of idoteids (Crustacea, Isopoda) inhabiting the Posidonia oceanica litter

The coexistence of three idoteid species in Posidonia oceanica litter raises the question of trophic diversity and their role in the litter degradation process. Hence, diet composition of Idotea balthica, Idotea hectica and Cleantis prismatica was studied using a combination of gut contents and stable isotopes analysis. Gut content observations indicate that P. oceanica dead leaves are an important part of the ingested food for the three species, although their tissues are constituted of only a small to medium fraction of P. oceanica carbon. Our results also underlined the potential role of these species in the degradation of P. oceanica litter by mechanically fragmenting the litter and by assimilating a small to medium fraction of carbon. Moreover, we showed that there were considerable inter- and intra-specific differences in diet composition. Diet differed between juveniles and adults for I. balthica. Crustaceans are an important food source for adults of I. balthica, while I. hectica indicated a major contribution of algal material. C. prismatica showed an intermediate diet. This trophic diversity is probably one of the factors allowing these species to coexist in the same biotope.     

Glycerol translocation in Condylactis gigantea

Sodium cyanide (NaCN) was used to partially uncouple respiration and photosynthesis in the symbiotic sea anemone Condylactis gigantea. NaCN significantly increased the ratio of gross photosynthesis to respiration in both intact tentacles and isolated zooxanthellae (Symbiodinium microadriaticum), increased carbon translocation from 17.7±3.5% of total fixed in controls to 43.5±5.8%, and doubled the amount of photosynthetically fixed carbon accumulating in the coelenterate host over that in controls. Only 2% of the non-particulate radioactivity recovered in the host tissue was ¹⁴C-glycerol when uninhibited symbiotic tentacles were incubated in ¹⁴C-bicarbonate for 1 h. At 10^-5 M NaCN, approximately 25% of the host nonparticulate radioactivity was recovered as ¹⁴C-glycerol, the absolute concentration of glycerol in the host tissue was three times higher than in controls, and ¹⁴C-glycerol was found in the medium. While glycerol has been proposed to play a major role in the translocation of photosynthetically fixed carbon from zooxanthellae to their coelenterate hosts, its concentration has never been measured in the animal and algal components of the symbiosis. The isolated zooxanthellae contained 3.62±0.33 mM glycerol, 26x the 0.141±0.02 mM found in the anemone. Aposymbiotic anemone tissue contained 0.169±0.06 mM glycerol. The rate of glycerol mineralization was not saturated even when exogenous glycerol levels were 70x internal concentrations. These data show that respiration and photosynthesis in symbiotic associations may be partially uncoupled by NaCN, and that this uncoupling allows the verification of the translocation and rapid catabolism of glycerol within the host.     

Long-term changes in populations of subtidal bivalves (Abra alba and A. prismatica) from the Bay of Morlaix (Western English Channel)

Two populations of Abra alba (Wood) and one of A. prismatica (Montagu) (Mollusca: Bivalvia) were studied over a 10 yr period (1977–1987) in two muddy fine-sand subtidal communities of the Bay of Morlaix, France. The survey provided an example of long-term changes in the three Abra spp. populations, which displayed synchronized changes, with a regular annual cycle and increasing densities during 1979–1980 related to the higher concentration of organic matter resulting from the Amoco Cadiz oil spill in March 1978. A. alba rapidly adapts its demographic strategy to eutrophic conditions by increasing its reproductive potential, growth, and abundance. During times of eutrophication, A. alba has three spawning periods and three recruitments per year as opposed to two spawning periods and two recruitments per year during oligotrophic conditions. Growth of the juveniles of this species is insignificant until spring for individuals recruited in the autumn, whereas individuals which settle during spring or summer display immediate rapid growth. A. prismatica has a low capacity to adapt to eutrophic conditions. It has one annual period of sexual maturation at the end of the summer, with spawning in September–October and settlement beginning in mid-November. Growth of the juveniles after settlement is also insignificant until April. These results enable comparison of the demographic strategies of these two sympatric species.     

Effects of changes in water salinity upon exercise and cardiac performance in the European seabass (<Emphasis Type="Italic">Dicentrarchus labrax</Emphasis>)

The European seabass is an active euryhaline teleost that migrates and forages in waters of widely differing salinities. Oxygen uptake (M_O2) was measured in seabass (average mass and forklength 510 g and 34 cm, respectively) during exercise at incremental swimming speeds in a tunnel respirometer in seawater (SW) at a salinity of 30 and temperature of 14°C, and their maximal sustainable (critical) swimming speed (U_crit) determined. Cardiac output (Q) was measured via an ultrasound flow probe on their ventral aorta. The fish were then exposed to acute reductions in water salinity, to either SW (control), 10, 5, or freshwater (FW, 0), and their exercise and cardiac performance measured again, 18 h later. Seabass were also acclimated to FW for 3 weeks, and then their exercise performance measured before and at 18 h after acute exposure to SW at 30. In SW, seabass exhibited an exponential increase in M_O2 and Q with increasing swimming speed, to a maximum M_O2 of 339±17 mg kg^–1 h^–1 and maximum Q of 52.0±1.9 ml min^–1 kg^–1 (mean±1 SEM; n=19). Both M_O2 and Q exhibited signs of a plateau as the fish approached a U_crit of 2.25±0.08 bodylengths s^–1. Increases in Q during exercise were almost exclusively due to increased heart rate rather than ventricular stroke volume. There were no significant effects of the changes in salinity upon M_O2 during exercise, U_crit or cardiac performance. This was linked to an exceptional capacity to maintain plasma osmolality and tissue water content unchanged following all salinity challenges. This extraordinary adaptation would allow the seabass to maintain skeletal and cardiac muscle function while migrating through waters of widely differing salinities.Communicated by S.A. Poulet, Roscoff     

Incidental capture,direct mortality and delayed mortality of sea turtles in Australia's Northern Prawn Fishery

The species composition, catch and mortality rates of sea turtles captured incidentally by the tiger prawn fishery on Australia's northern coast in 1989 and 1990 were estimated by monitoring the fishery's catch. In 1990, the delayed rate of mortality from damage was estimated and the size composition was measured. Five species of turtles were captured: the flatback (Natator depressa, 59% of the total), loggerhead (Caretta caretta, 10%), olive ridley (Lepidochelys olivacea, 12%), green turtle (Chelonia mydas, 8%) and hawksbill (Eretmochelys imbricata, 5%). The turtle catches varied with water depth: the highest catch rates (0.068±0.006 turtles per trawl) were from trawls in water between 20 and 30 m deep, relatively few turtles (10%) were captured in water deeper than 40 m (25% of trawls). Catch rates varied with time of year: the highest catch rates were 0.098 (±0.013) turtles per trawl in winter. There was no significant difference in the overall catch rate (²= 0.047; p=0.8111; df=1) but a significant difference in mortality rate (²= 3.99; p<0.05; df=1) between the two years. The incidence of capture in the commercial fishery was 0.051 (±0.003) turtles per trawl towed for about 180 min, with 0.007 (±0.001) turtles per trawl drowning in the nets. There were no significant differences in the catch and mortality rates between the two years for any of the turtle species except the loggerhead, which had a significantly (² = 11.029; p=0.0013; df=1) lower catch rate in 1990 (0.002±0.001 turtles per trawl) than in 1989 (0.008±0.002 turtles per trawl), and a significantly higher mortality in 1990 (33%) than in 1989 (19%). Catch rates and mortality varied between the species: the flatback had the highest catch rate (0.030±0.002 turtles per trawl) but the lowest mortality (10.9%); the loggerhead had a catch rate of 0.005±0.001 turtles per trawl, and high mortality (21.9%); the olive ridley had a catch rate of 0.006±0.001 turtles per trawl and a low mortality (12.5%); the green turtle's catch rate was 0.004±0.001 per trawl and mortality 12.0%; the hawksbill had the lowest catch rate (0.002±0.001 turtles per trawl) but highest mortality (26.4%). Based on the fishing effort (27 049 d for 1989 and 25 746 d for 1990), we estimate that 5 503 (±424) turtles were caught and returned to the sea in 1989 and 5 238 (±404) in 1990, of which 567±140 drowned in 1989 and 943±187 in 1990. In 1990, an estimated 25% of all captured turtles suffered some non-lethal damage; an estimated 21% of turltes were captured comatose and 4% were injured. We conclude that, considering other threats, trawl-induced drowning is not the major impact on turtle populations in northern Australia, but that measures to reduce drowning and delayed mortality would be desirable.     

Growth and metamorphosis of Aplysia oculifera larvae in laboratory culture

Eggs of Aplysia oculifera (Adams and Reeve, 1850) were incubated in the laboratory. They hatched 8 to 9 d after spawning. Shell length (SL) of the hatched larvae was 102±2 m. Larvae were fed on the unicellular algae Isochrysis galbana in a concentration of 10⁴ cell ml^-1, and after 45 to 60 d grew to a maximum SL of 385±11 m. Larvae survived up to 330 d. A total of 12 species of algae from the natural habitat of A. oculifera were examined as metamorphosis inducers. Red algae Dasia sp., Jania sp., Hypnea sp. and Liagora sp. induced metamorphosis in 66.7±21.2, 28.3±17.7, 26.0±18.5 and 4.0±8.0% of the larvae, respectively. Green algae Enteromorpha intestinalis and Ulva sp. induced metamorphosis in 37.0±11.0 and 9.0±10.4% of the larvae, respectively. Cladophora sp. and Codium dichotomum, and the brown algae Padina pavonia, Colpomenia sinuosa, Hydroclathrus clathratus and Cystoseira sp. did not induce metamorphosis. There was no significant difference in the rate of metamorphosis between young (2 to 4 mo) and old (6 to 8 mo) larvae. Postmetamorphic juveniles grew and developed only when fed with E. intestinalis. They grew to a body length of>8 mm in 50 d. Postmetamorphic juveniles did not survive on other algae. The longevity of the planktonic A. oculifera larvae supports the hypothesis that the larvae can exist in the plankton and survive for several months until the next recruitment. The advantage of non-specificity in metamorphosis induction is discussed.     

Effect of elevated temperature on aerobic respiration of coral recruits

Metabolic rates provide a valuable means to assess the condition of early life stages of scleractinians, but their small biomass creates a signal-to-noise problem in a confined respirometer. To avoid this problem, measurements of the oxygen diffusion boundary layer (DBL) and Ficks first law were used to calculate the respiration rate of coenosarc tissue on recruits (i.e., colonies 5–14 mm diameter) of Porites lutea (Edwards and Haime, 1860) exposed to two temperatures at a flow speed of 0.6 cm s^–1. All experiments were completed in Moorea, French Polynesia, between November and December 2003. At 26.8°C, the DBL was 565±55 µm thick, the oxygen saturation adjacent to the tissue was 80±3%, and the mean respiration of the coenosarc was 1.2±0.1 µl O₂ cm^–2 h^–1 (all values mean ± SE, n=10). Exposure to 29.7°C for 24–48 h did not affect the DBL thickness but significantly reduced the oxygen saturation adjacent to the tissue (to 74%) and increased the mean respiration rate by 35%. As the small corals differed slightly in size, in a uniform flow speed they experienced dissimilar flow environments as characterized by the Reynolds number (Re), thereby creating the opportunity to test the flow dependency of respiration. At 26.8°C, respiration and Re were unrelated, but at 29.7°C, the relationship was positive and statistically significant. Thus, respiration of small corals may not be mass transfer limited at low temperature, but relatively small increases in temperature may result in an increased metabolic rate leading to mass transfer limitation and flow-dependent rates of respiration.Communicated by J.P. Grassle, New Brunswick     

Population biology of hyperbenthic crustaceans in a cold water environment (Conception Bay,Newfoundland). II.<Emphasis Type="Italic"> Acanthostepheia malmgreni</Emphasis> (Amphipoda)

Seasonal population dynamics of the gammarid Acanthostepheia malmgreni Goës in Conception Bay, Newfoundland, were examined from October 1998 to November 2000. This species exhibited a 2.5-year life span, with the reproductive cycle correlating with seasonal phytoplankton flux. Females were semelparous and died following a 5-month brooding period and the subsequent release of juveniles in April and May. The biennial life cycle of this population should result in the presence of two cohorts in the hyperbenthos at any given time. However, the cohorts alternated in strength from year to year, which affected annual density, biomass and production during the study period. Densities were 64±87 ind. per 100 m³ in 1999 and 491±492 ind. per 100 m³ (mean±SD) in 2000. Secondary production was estimated at 18–44 mg C m^–2 in 1999 and 180–311 mg C m^–2 in 2000. The annual P/B ratios were 0.89 and 2.27 in 1999 and 2000, respectively. Growth varied both among and within cohorts, with different life-history stages exhibiting variable growth rates ranging from 0 to 12 mg dry mass month^–1.Communicated by J.P. Grassle, New Brunswick     

Calorific,ash, carbon and nitrogen content in relation to length and dry weight of Parathemisto gaudichaudi (Amphipoda: Hyperiidea) in the North East Atlantic Ocean

The calorific, ash, carbon and nitrogen content, length and dry weight were determined for the hyperiid Parathemisto gaudichaudi (Guerin). Regression equations for all these variables were determined so that they can be estimated by calculation from measurements of length of the hyperiid. Mean values for total nitrogen and carbon were 7.79±0.85% and 36.80±4.18% of the dry weight, respectively. The carbon to calorific equivalent for P. gaudichaudi was 10.37 kcal g^-1 carbon (9.13 kcal g^-1 when corrected for nitrogen). The calorific value for ash-free adult P. gaudichaudi was 5.138 kcal g^-1±1.309 (4.510 kcal g^-1 when corrected for nitrogen). This large variation in the calorific content (coefficient of variation of 25.84%) can be accounted for largely by variation in the ash content (coefficient of variation of 21.84%). The calorific value determined for P. gaudichaudi is similar to that measured for other carnivorous crustaceans and adds support to the hypothesis that animals with high calorific content have a low fecundity and an energy-rich store which can be used as a buffer during unfavourable periods in their life.     

Distribution of tetrodotoxin in various organs of the starfish Astropecten polyacanthus

Tissues of various organs of the starfish Astropecten polyacanthus collected in the Hiroshima Prefecture from April 1985 to June 1986 were analyzed for lethal potency by the assay method for tetrodotoxin. The ovary showed the highest potency (47 to 1 450 MU g^-1), followed by the digestive organs (<10 to 960 MU g^-1) and the exoskeleton including spines and tube-feet (<10 to 170 MU g^-1). The pyloric caecum and testis were less toxic. Overall toxicity was remarkably higher in females (2 060±382 MU, mean±SE) than in males (1 106±214 MU).     

Temporal variation in protein, carbohydrate, and lipid concentrations in Paramuricea clavata (Anthozoa, Octocorallia): evidence for summer–autumn feeding constraints

Temporal variations in protein, carbohydrate, and lipid levels were studied in a passive suspension feeder, the gorgonian Paramuricea clavata. The samples were collected every month for mature and immature colonies over a three-year period (1997–2000). The relationship between biochemical composition and reproductive output was examined on the basis of the 1998 and 1999 data. In female and male P. clavata colonies, the tissue displayed differences in lipid concentrations only in winter–spring, due to the high lipid levels attained by female colonies in this period. Immature colonies showed significant differences in lipid concentration only with respect to mature females in spring. There were clear seasonal trends in the lipid and carbohydrate levels in P. clavata, with maximum values in winter–spring [male lipid 212±75 SD μg mg⁻¹ of organic matter (OM) and female lipid 274±103 SD μg mg⁻¹ of OM; male and female carbohydrate 68±14 SD μg mg⁻¹ of OM], coinciding with maximum food concentration/quality, and minimum values in summer–autumn (male and female lipid 155±57 SD μg mg⁻¹ of OM; male and female carbohydrate 56±14 SD μg mg⁻¹ of OM), coinciding with low food concentration/quality. The relationship between reproductive output and tissue concentrations of lipids, carbohydrates, and proteins was not straightforward, although there was an evident overlap of the lipid accumulation and the gonadal development. The results of this study show that protein, carbohydrate, and lipid levels may provide a record of episodes in the ecological cycle bearing on the trophic aspects of the target species. The results indicate that information on seasonal biochemical levels may explain benthopelagic coupling processes, provided factors such as natural diet, feeding rates, reproduction, and growth are well understood.     

Mangrove fish-communities in tropical Queensland,Australia: Spatial and temporal patterns in densities,biomass and community structure

Regular daylight sampling over 13 mo (February 1985–February 1986) in and adjacent to intertidal forested areas, in small creeks and over accreting mudbanks in the mainstream of a small mangrove-lined estuary in tropical northeastern Queensland, Australia, yielded 112 481 fish from 128 species and 43 families. Species of the families Engraulidae, Ambassidae, Leiognathidae, Clupeidae and Atherinidae were numerically dominant in the community. The same species, with the addition ofLates calcarifer (Latidae).Acanthopagrus berda (Sparidae) andLutjanus agentimaculatus (Lutjanidae) dominated total community biomass. During high-tide periods, intertidal forested areas were important habitats for juvenile and adult fish, with grand mean (±1 SE) density and biomass of 3.5±2.4 fish m^–3 and 10.9±4.5 g m^–3, respectively. There was evidence of lower densities and less fish species using intertidal forests in the dry season (August, October), but high variances in catches masked any significant seasonality in mean fish biomass in this habitat. On ebb tides, most fish species (major families; Ambassidae, Leiognathidae, Atherinidae, Melanotaeniidae) moved to small shallow creeks, where mean (±1 SE) low-tide density and biomass were 31.3±12.4 fish m^–2 and 29.0±12.1 g m^–2, respectively. Large variances in catch data masked any seasonality in densities and biomasses, but the mean number of species captured per netting in small creeks was lowest in the dry season (July, August). Species of Engraulidae and Clupeidae, which dominated high-tide catches in the forested areas during the wet season, appeared to move into the mainstream of the estuary on ebbing tides and were captured over accreting banks at low tide. Accreting banks supported a mean (±1 SE) density and biomass of 0.4±0.1 fish m^–2 and 1.7±0.3 g m^–2, respectively, at low tide. There were marked seasonal shifts in fish community composition in the estuary, and catches in succeeding wet seasons were highly dissimilar. Comparison of fish species composition in this and three other mangrove estuaries in the region revealed significant geographic and temporal (seasonal) variation in fish-community structure. Modifications and removal of wetlands proposed for north Queensland may have a devastating effect on the valuable inshore fisheries of this region, because mangrove forests and creeks support high densities of fish, many of which are linked directly, or indirectly (via food chains) to existing commercial fisheries.Contribution No. 493 from the Australian Institute of Marine Science     

Population biology of hyperbenthic crustaceans in a cold water environment (Conception Bay,Newfoundland). I.<Emphasis Type="Italic"> Mysis mixta</Emphasis> (Mysidacea)

Seasonal population dynamics of Mysis mixta Lilljeborg were studied from December 1998 to November 2000 at a 240 m deep site in Conception Bay, Newfoundland. At this depth, temperature was <0°C and salinity between 32.0 and 34.0 psu year-round. The spring phytoplankton bloom began in early or late March and reached a maximum in late April to mid-May. M. mixta exhibited a highly synchronised life cycle, with spawning and mating occurring in October to November, embryos brooded for ~5 months, and juveniles released during spring bloom sedimentation in April and May. Females were semelparous and died at age 2.5 years, following release of juveniles in spring, whereas the majority of mature males died at age 2 years, following mating in November. The biennial life cycle of this population resulted in the presence of two cohorts in the hyperbenthos at any given time. Variation in density and biomass was low among cohorts but high within cohorts, the latter probably due to the high motility of mysids. Densities in 1999 and 2000 were 242±379 and 544±987 ind. per 100 m³ (mean±SD), respectively. Although growth rates were similar between years, rates measured from changes in dry mass differed both seasonally and among life-history stages (range from –4 to 7 mg month^–1). Annual secondary production was estimated at 29–73 mg C m^–2 in 1999 and 53–205 mg C m^–2 in 2000. The annual P/B ratios were 1.62 and 1.19 in 1999 and 2000, respectively.Communicated by J.P. Grassle, New Brunswick     

Energy content at metamorphosis and growth rate of the early juvenile barnacle<Emphasis Type="Italic"> Balanus amphitrite</Emphasis>

The energetic cost of metamorphosis in cyprids of the barnacle Balanus amphitrite Darwin was estimated by quantification of lipid, carbohydrate and protein contents. About 38–58% (4–5 mJ individual^–1) of cypris energy reserves were used during metamorphosis. Lipids accounted for 55–65%, proteins for 34–44% and carbohydrates for <2% of the energy used. Juveniles obtained from larvae fed 10⁶ cells ml^–1 of Chaetoceros gracilis were bigger (carapace length: 560–616 µm) and contained more energy (5.56±0.10 mJ juvenile^–1) than their counterparts (carapace length: 420–462 µm; energy content: 2.49±0.20 mJ juvenile^–1) obtained from larvae fed 10⁴ cells ml^–1. At water temperatures of 30°C and 24°C and food concentrations of 10⁴ and 10² cells ml^–1 (3:1 mixture of C. gracilis and Isochrysis galbana) as well as under field conditions (26.9±3.1°C and 2.2±0.8 µg chlorophyll a l^–1), juveniles obtained from larvae fed the high food concentration grew faster than juveniles obtained from larvae fed low food concentration until 5 days post-metamorphosis. Laboratory experiments revealed a combined effect of early juvenile energy content, temperature and food concentration on growth until 5 days post-metamorphosis. After 10 days post-metamorphosis, the influence of the early juvenile energy content on growth became negligible. Overall, our results indicate that the energy content at metamorphosis is of critical importance for initial growth of juvenile barnacles and emphasize the dependency of the physiological performance of early juvenile barnacles on the larval exposure to food.Communicated by O. Kinne, Oldendorf/LuheAn erratum to this article can be found at