ALBERT

Description: Factors responsible for aggregations of jumbo flying squid Dosidicus gigas, an important component of the marine food web and target of commercial fisheries off the Costa Rica Dome in the Eastern Tropical Pacific Ocean (ETP), were examined during 2 years of different extreme oceanographic conditions: fall 1997 El Niño and fall 1999 La Niña. A high abundance of squid occurred in association with the well-developed countercurrent ridge (upwelling) off the Costa Rica Dome during fall 1997, but not during fall 1999, when the countercurrent ridge was less developed. Two features of the well-developed countercurrent ridge were considered important for the occurrence of high jumbo flying squid concentrations. Firstly, subsurface chlorophyll a (chl a) maxima were formed along the countercurrent ridge, resulting in integrated chl a concentrations in the upper 100 m being relatively high considering the generally low productivity of the ETP during an El Niño event. Secondly, a strong salinity front formed along the North Equatorial Countercurrent, which is possibly responsible for retention of jumbo flying squid in the ridge. Large yellowfin tuna Thunnus albacares, which mainly feed on micronekton (small fishes, cephalopods and swimming crabs), as do jumbo flying squid, were also more highly concentrated along the countercurrent ridge during 1997 than during 1999. It was noted that skipjack tuna Katsuwonus pelamis and small yellowfin tuna, which mainly feed on zooplankton, were associated with the equatorial ridge in the ETP, indicating that prey faunal components may also play an important part in the close association of jumbo flying squid with the countercurrent ridge.

Description: Age, growth and maturity parameters were examined for the southern Australian ommastrephid squid Nototodarus gouldi. Squid were obtained from the fishing ports of: Ulladulla, New South Wales; Port Lincoln, South Australia; Lakes Entrance, Victoria; and Hobart, Tasmania. Squid were collected during 2 seasonal periods: summer/autumn-caught (warm-season squid) and spring-caught (cool-season squid) over 2 consecutive years (2000, 2001). N. gouldi is a sexually dimorphic species, with females generally reaching larger sizes than males. Initial genetic analysis has found only a single species in Australian waters. Statolith ageing revealed that squid completed their life cycle in 〈1 yr, and appear to hatch throughout the year. Trends in size, growth and maturity varied considerably between sites, seasons and years. Squids hatched in summer/autumn grew consistently faster than squid that hatched in winter/spring, presumably due to the influence of temperature on growth. Squid in 1999/2000 also grew faster than squid in 2000/2001. Growth of female squid in winter correlated with sea surface colour (SSC) during peak hatch periods, but the SSC relationship did not exist for males. Ulladulla squid were generally smaller, younger, had smaller gonads than most other squid and were possibly a smaller morph of the species. Tasmania and Lakes Entrance tended to have larger older individuals with larger gonads, while Port Lincoln was variable and intermediate. However, during spring 2001 both Tasmania and Port Lincoln had individuals that were much smaller than those of the other seasons for these sites, and were more like those from Ulladulla. Trends in age of mature individuals showed considerable variability (over 100 d from youngest to oldest) and there appeared to be a cline across all sites and seasons. Arrow squid appear to reveal marked plasticity in age, growth and maturity parameters, but currently the extent to which the environment or genetics control plasticity is unclear.

Description: Albatrosses have among the most remarkable travelling capacities of any extant animal. However, previous studies regarding their movements at sea have mainly focused on breeding birds commuting between the nest site and offshore feeding grounds. In this study, we compare the movement patterns and at-sea activity of breeding and inter-breeding black-browed albatrosses Diomedea melanophris from the Falkland Islands. Data were recorded via global location and activity sensors for 26 incubating birds [during single foraging trips lasting 6.8 d on average) and 6 inter-breeding individuals (during non-stop offshore journeys of 127.5 d on average). Our results showed that foraging black-browed albatrosses utilise vast offshore areas (the average foraging area was 102000 +_ 132 000 km2 by incubating birds and 1552 000 * 970 000 km2 by inter-breeding birds). However, mean forag~ngr ange was similar in both groups (691 * 330 km and 680 t 192 km by incubating and interbreeding birds, respectively) as were their core foraging areas and their at-sea activity patterns. Our results thus indicate that black-browed albatrosses from the Falkland Islands, which represent the largest albatross population world-wide (ca 800 000 individuals), mainly rely on marine resources available within the Patagonian Shelf area. Although this hghly productive continental shelf is the largest of the Southern Hemisphere, rapid development of industrial fisheries currently results in the removal of over 1.4 million tonnes of fish and squid per year in this zone. As our data also show significant spatio-temporal overlap between human and albatross fishing activities within the Patagonian Shelf, we anticipate major detrimental effects on the albatross population in terms of competition for food and additional mortality caused by bird bycatch.

Description: Squids typically demonstrate considerable plasticity in individual growth rates. However, it is not known if individuals growing at different rates also differ at lower levels of organisation. We wished to determine if Sepioteuthis lessoniana individuals that were larger than predicted for their age differed in their digestive gland and mantle muscle tissue proximal composition or mantle muscle structure, compared with individuals that were smaller for their age than predicted. The residual, the difference between the observed size-at-age and that predicted by the growth equation, was used as a measure of the difference in an individual's lifetime growth from the population average. Individual squid varied considerably in their size-at-age, with juveniles showing less variation than adults. Juveniles had greater concentrations of lipid in their muscle tissue, perhaps due to an emphasis on storing energy reserves in this critical period of their life. Differences in biochemical constituents in both the digestive gland and muscle tissue were not related to the size-at-age of individuals, despite biochemical make-up being the lowest organisational level of growth. This may be due to whole animal growth and changes in biochemical composition occurring on different time scales. There was no relationship between the size-at-age of individuals and average mantle muscle fibre size. A strong relationship, however, existed between the size of mantle muscle blocks and the size-at-age of individuals for both juvenile and adult individuals, suggesting that larger muscle blocks are related to both body size and faster individual growth rates. This study demonstrates a clear relationship between mantle muscle structure and growth and the size-at-age of S. lessoniana individuals.

Description: Large Protista of unknown taxonomic affinities are described from 3 species of coleoid squids, and are reported from many other species of cephalopods. The white to yellow-orange, ovoid cyst-like parasites are partially embedded within small pockets on the surface of the gills, often in large numbers. Except for a holdfast region on one side of the large end, the surface of the parasite is elaborated into low triangular plates separated by grooves. The parasites are uninucleate; their cytoplasm bears lipid droplets and presumed paraglycogen granules. Trichocysts, present in a layer beneath the cytoplasmic surface, were found by transmission electron microscopy to be of the dinoflagellate type. Further studies are needed to clarify the taxonomic position of these protists.

Description: A new species of giant unicellular parasite inhabiting the gills of squid hloroteuthis robusta is described from specimens collected from the northeastern Pacific Ocean. Hochbergia moroteuthensis gen. et sp. nov. belongs to a recently reported group of protistans whose taxonomic affinities are as yet unknown. Members of the group parasitize cephalopods and have a characteristic aspect: most of the body wall is raised into close-fitting triangular plates and there is a holdfast region, devoid of plates, by which the parasites attach to the host. H. moroteuthensis is the first species of the group to be named. The general form of the body, the precise number and arrangement of plates, and the morphology of the holdfast reglon are described.

Description: Analysis of stomach contents and predator-prey relations of 168 swordfish from the western North Atlantic Ocean is presented. The predominant food of swordfish is squid (82% by frequency of occurence) followed by fish (53%) consisting primarily of gladis, scombrids, butterfish, bluefish, and sand lance. Average food volume in stomach is 1% of average body weight. Estimates of daily ration range from 0.94% to 1,6% of avergae body weight, with yearly consumption ranging from 3.4 to 5.8 times average body weight per year. The prey biomass consumed by the sowrdfish population in the Georges Bank area is estimated to range from 2,100 to 11,000 mt over a residency time of 5 mo.

Description: As one of the elements for a model on the food requirements of Humboldt penguins Spheniscus humboldti we determined, via gas respirometry, metabolic rates while swimming and resting in water. During rest in water at 19°C Humboldt penguins (mean body mass 3.6 kg) required 5.95 W kg-1. This corresponds to a thermal conductance in water of 0.2975 W (kg °C)-1 (at Ta 19°C and assuming a Tb of 39°C). When swimming in a 20 m long channel, metabolism rose from 8 W kg-1 at a speed of 0.6 ms-1 to 23.1 W kg-1 at 2.2 m s-1. Transport costs (the cost to move 1 kg of body mass over a distance of 1 m) reached a minimum at 1.4 ms-1 with 8.1 J (kg m)-1, which corresponds to 0.89 J (Nm)-1. We corrected for acceleration and deceleration in the channel to determine transport costs of free-ranging Humboldt penguins travelling at sea, which were calculated as 7 J (kg m)-1 (0.71 J [Nm]-1), at 1.7 m s-1. Birds feeding chicks need to balance the costs of either (1) returning to the breeding island for the night and travelling back to the feeding grounds in the morning or (2) incurring increased thermoregulatory costs associated with resting at sea overnight. Simple calculations show that at water temperatures of 19°C we expect Humboldt penguins to show a tendency to remain at sea overnight if foraging areas are 〉4 km from their island. In colder waters (12°C), this distance increases to 〉9 km. Using previously published data on at-sea activity of Humboldt penguins, we found that foraging costs during chick rearing amount to 340 g anchovies d-1. Finally, we present a general model to convert Humboldt penguin activity data at sea to food requirements.

Description: The combined and interactive effects of climatic and ecological factors are rarely considered in marine communities. We designed a factorial field experiment to analyze (1) the interactive effects of ambient UV radiation and consumers; and (2) the effects of photosynthetically active radiation (PAR 400 to 700 nm), UVA (320 to 400 nm) and UVB (280 to 320 nm) radiation on a marine hard-bottom community in Nova Scotia, NW Atlantic. Species recruitment and succession on ceramic tiles were followed for 5 mo. We found strong negative UV effects on biomass and cover of the early colonizing macroalga Pilayella littoralis, whereas UVB was more harmful than UVA radiation. Consumers, mainly gammarid amphipods, increased P. littoralis biomass when UV was excluded, probably through fertilization. These initially strong and interacting UV and consumer effects on total biomass and cover diminished as species succession progressed. Species diversity was not affected by experimental treatments, but significant shifts in species composition occurred, especially at the recruitment stage. Red algae were most inhibited by UV, whereas sedentary invertebrates and some brown algae tended to increase under UV exposure. Consumers suppressed green and filamentous brown algae, but favored the other groups. Again, these effects diminished during the later stages of succession. We conclude that UV radiation can be a significant structuring force in early successional benthic communities, and that consumers can mediate its effects.

Description: In the Baltic Sea, rye tested how short nutrient pulses of different lengths and frequencies affect macroalgae, epiphytes, grazers and their interactions. We hypothesized that even small-scale variations in nutrient supply may have significant impacts by favoring fast-growing epiphytes which can cause large-scale declines of canopy-forming macroalgae. In a factorial field experiment single plants of the canopy-forming macroalga Fucus vesiculosus with and without epiphytes were exposed to pulses of elevated nutrients (N and P) over 25 d. Five 1 h pulses given every 5 d had no significant effects. A single 5 h pulse increased the epiphyte load but not F. vesiculosus growth rate. In contrast, increasing epiphyte load caused F. vesiculosus growth rate to decline and attracted higher densities of gastropod grazers. These results indicate that a single nutrient pulse can have rapid direct and indirect effects on macroalgae and their associated epiphytes and grazers. Temporal variability of nutrient supply (five 1 h vs one 5 h pulse) plays a significant role in determining the response of primary producers and consumers to elevated nutrients.