ALBERT

Description: The process of fluid release from the subducting slab beneath the Izu arc volcanic front (Izu VF) was examined by measuring B concentrations and B isotope ratios in the Neogene fallout tephra (ODP Site 782A). Both were measured by secondary ion mass spectrometry, in a subset of matrix glasses and glassy plagioclase-hosted melt inclusions selected from material previously analyzed for major and trace elements (glasses) and radiogenic isotopes (Sr, Nd, Pb; bulk tephra). These tephra glasses have high B abundances (∼10–60 ppm) and heavy δ11B values (+4.5‰ to +12.0‰), extending the previously reported range for Izu VF rocks (δ11B, +7.0‰ to +7.3‰). The glasses show striking negative correlations of δ11B with large ion lithophile element (LILE)/Nb ratios. These correlations cannot be explained by mixing two separate slab fluids, originating from the subducting sediment and the subducting basaltic crust, respectively (model A). Two alternative models (models B and C) are proposed. Model B proposes that the inverse correlations are inherited from altered oceanic crust (AOC), which shows a systematic decrease of B and LILE with increasing depth (from basaltic layer 2A to layer 3), paralleled by an increase in δ11B (from ∼+1‰ to +10‰ to +24‰). In this model, the contribution of sedimentary B is insignificant (〈4% of B in the Izu VF rocks). Model C explains the correlation as a mixture of a low-δ11B (∼+1‰) ‘composite’ slab fluid (a mixture of metasediment- and metabasalt-derived fluids) with a metasomatized mantle wedge containing elevated B (∼1–2 ppm) and heavy δ11B (∼+14‰). The mantle wedge was likely metasomatized by 11B-rich fluids beneath the outer forearc, and subsequently down dragged to arc front depths by the descending slab. Pb–B isotope systematics indicate that, at arc front depths, ∼53% of the B in the Izu VF is derived from the wedge. This implies that the heavy δ11B values of Izu VF rocks are largely a result of fluid fractionation, and do not reflect variations in slab source provenance (i.e. subducting sediment vs. basaltic crust). Since the B content of the peridotite at the outer forearc (7–58 ppm B, mean 24±16 ppm) is much higher than beneath the arc front (∼1–2 ppm B), the hydrated mantle wedge must have released a B-rich fluid on its downward path. This ‘wedge flux’ can explain (1) the across-arc decrease in B and δ11B (e.g. Izu, Kuriles), without requiring a progressive decrease in fluid flux from the subducting slab, and (2) the thermal structure of volcanic arcs, as reflected in the B and δ11B variations of volcanic arc rocks.

Description: Siderophores are low molecular weight, iron-chelating ligands produced by nearly all microorganisms. Fungi synthesize a wide range of hydroxamate siderophores. This review considers the chemical and biological aspects of these siderophores, their distribution amongst fungal genera and their possible applications. Siderophores function primarily as iron transport compounds. Expression of siderophore biosynthesis and the uptake systems is regulated by internal iron concentrations. Transport of siderophores is an energy-dependent process and is stereoselective, depending on recognition of the metal ion coordination geometry. In addition to transporting iron, siderophores have other functions and effects, including enhancing pathogenicity, acting as intracellular iron storage compounds and suppressing growth of other microorganisms. Siderophores can complex other metals apart from iron, in particular the actinides. Because of their metal-binding ability there are potential applications for siderophores in medicine, reprocessing of nuclear fuel, remediation of metal-contaminated sites and the treatment of industrial waste.

Description: Fishery statistics for two abundant commercial squid, Illex argentinus (Ommastrephidae) and Loligo gahi (Loliginidae), in Falkland Islands waters (southwest Atlantic) between 1987 and 1999 were analysed. The areas of the highest densities of the two species are usually separated, with I. argentinus most abundant to the north-west of the Islands in February–May and L. gahi to the south-east in February–May and August–October. However, in some years, I. argentinus intrude in great numbers into nursery or feeding areas of L. gahi in April and May. It could, therefore, affect, either directly (via predation) or indirectly (by competition for food), the abundance and recruitment of the second cohort of L. gahi, exploited around the Islands between April and October. Catch per unit effort (CPUE) of I. argentinus in February–March did not correlate with that of L. gahi in February–May. In contrast, the CPUE of I. argentinus in April–May was negatively correlated with that of L. gahi in April–May and August–October of the same year. Possible reasons for these inverse abundance patterns of the two squid species, and their implications for fisheries management are discussed.

Description: In the Falkland waters, squid have maximum stomach fullness and lowest hunting activity in the evening. During the night, hunting activity increased until dawn while food was digesting, except for a short period around and after midnight when squid activity decreased.

Description: Cephalopods constitute a valuable resource of Portuguese fisheries, but there are no data on the adequacy of legal mesh size with regards to minimum landing size (MLS) (or weight). In the autumn of 1998 and the spring and summer of 1999 surveys were carried out off the northern coast of Portugal to study codend selectivity of finfish bottom trawls. Mesh sizes used were 65, 80 and 90 mm (full mesh size). During these surveys primarily targeting fish species, data were obtained for the octopus, Octopus vulgaris, the European squid, Loligo vulgaris and the broadtail shortfin squid, Illex coindetii. For the octopus, selectivity parameters were estimated for the 65 mm codend (L50 between 8.4 and 9.7 cm and selection factor (SF) 1.3 and 1.5) and for the 80 mm codend in the summer (L50 14.2 cm and SF 1.9). For the European squid, selectivity parameters were estimated in the autumn survey for the 80 and 90 mm mesh size codends (L50 9.7 and 11.4 cm, respectively, and SF 1.3 for both codends). For the broadtail shortfin squid, selectivity parameters were estimated in the summer for the 65 mm mesh size codend (L50 9.5 cm and SF 1.5). Considering that the finfish bottom trawl fishery uses a minimum mesh size of 65 mm, it is concluded that a high proportion of small octopus that has a minimum landing weight (MLW) of 0.75 kg (corresponding to a dorsal mantle length of 11.8 cm) is retained. For the European squid, whose MLS is 10 cm, a 65 mm mesh size would also retain an extremely high proportion of undersized individuals, but these occur in very small numbers in the fishery. The broadtail shortfin squid has no established MLS.

Description: Population structure and reproductive patterns of the long-finned squid Loligo plei off the coast of Santa Catarina, southern Brazil, were analysed from the biological samples of commercial catches landed in the Itajaı́ harbour from April 1995 to February 1998. The species were recruited to the trawl fishery at 130 mm mantle length (ML) and males were, on average, nearly 1.3 times larger than females. The exponents of males and females ML–weight relationships were 1.89 and 2.07, respectively, and differed significantly between maturity stages. Cohorts of both sexes did not persist into their second year, a feature that, coupled with the scarcity of spent animals, provided evidence for semelparity with nearly 1 year life span. An extended seasonal breeding and spawning pattern was characterised with a large reproduction event concentrated during the summer months extending through autumn and winter. It is suggested that the summer spawners hatch during the summer–early autumn, recruit to the fishery in the spring and reach maturity in the following summer, at the age of nearly 1 year. Squid spawned during the winter will hatch during winter–early spring, recruit to the fishery during the summer and autumn and spawn in their second winter. Between summer and winter spawning events, continuous spawning activity produce several microcohorts detected in trawlers catch. Summer spawners sustain the most important commercial concentrations. The relationship between L. plei population structure, seasonal abundance and the dynamics of environmental conditions off southern Brazil is discussed.

Description: The feeding habits of Beryx splendens and B. decadactylus were determined from stomach contents obtained on a monthly basis during commercial fishing off the Canary Islands in 1996–1997. Changes in diets were studied in relation to predator size and seasonal variation in the food composition. The diet of both species has much in common with regard to its main components of small fishes, crustaceans and cephalopods. More important differences were found in the fish prey of B. decadactylus. A variation in the diet of B. splendens was observed according to its length. Seasonal variations in feeding habits were associated with either variations in the abundance of prey or variations in the depth distribution of predator and prey.

Description: Experiments were conducted to investigate growth and proteolytic activity of the common octopus Octopus vulgaris, reared with different diets and ration levels during first feeding. Four ration levels were tested, 0.2, 2, 4 and 10 Artemia nauplii ml−1 day−1 and co-feeding techniques were tested using 10 Artemia nauplii ml−1 day−1 plus three different compound millicapsules. Total proteolytic activity, trypsin and chymotrypsin levels were recorded from eggs, hatchlings and during the first month of paralarval rearing. Five days after hatching, paralarval weight and proteolytic activity was dependent on food ration. The low-food treatment did not lead to an increase in hatchling weight, in contrast with the positive increase of the other treatments. After 20 days, best survival was observed in treatments fed 2 and 4 nauplii ml−1 day−1. High nauplii rations of 10 nauplii ml−1 day−1 plus millicapsule diet treatments produced higher growth and higher proteolytic, trypsin and chymotrypsin levels, but poor survival. Total proteolytic activity was correlated with paralarval weight, whereas trypsin and chymotrypsin were maintained at hatchling levels only for the high food and co-feeding treatments, and decreased in the others. The trypsin activity in the high-food treatment showed a sharp increase after 15 days and 880 μg of the mean dry weight (2.5 times hatchling weight). Millicapsules were ingested by the paralarvae after 5 days but did not lead to a significant increase in weight. Enriched Artemia nauplii seem to be useful only as an initial diet until a doubling in hatchling weight is achieved. This period can extend from 11 to 14 days at 20 °C, after which a larger prey and/or suitable microdiet is required.

Description: Several species of migratory, warm-water, oceanic fishes invaded Oregon waters during the summer of 1997. Also, the jumbo squid (Dosidicus gigas), common in the eastern tropical Pacific, was reported for the first time in 1997 and was caught in large numbers. The occurrence of these oceanic nekton was associated with inshore advection of anomalously warm water. During 1998, after arrival of the main El Niño signal, some warm-water coastal fishes appeared off Oregon. However, unlike observations off California, fewer species of warm-water coastal fishes were noted during the 1997–98 El Niño than during the 1982–83 El Niño.

Description: The common octopus, Octopus vulgaris Cuvier, 1797 is the most important cephalopod species in catches of the artisanal trap fishery in Canary Islands waters. Based on monthly samplings carried out off Gran Canaria (Canary Islands), 760 specimens of the common octopus, ranging from 4.8 to 165 mm ventral mantle length, were studied from June 1996 to July 1997, and from December 1997 to June 1999. The length–weight relationships found were W=0.0007×VML3.096 (n=760;r=0.95), W=0.0007×VML3.112 (n=481;r=0.86), W=0.0007×VML3.098 (n=247;r=0.77), for all the specimens caught, males and females, respectively. The proportion of males was significantly higher than females. Males predominated in all size intervals. Males and females become sexually mature at 105 and 113 mm of VML, respectively. Maturation and spawning occur all year around, with more intensity from January to July, with a peak in April. There is a second spawning period in October–November. The number of spermatophores produced increased with length and maturity stage. The production of spermatophores by individual body weight fluctuated from 0.29 to 0.03 spermatophores/g. The number of oocytes per gram of body weight fluctuated from 108 to 465. The real fecundity oscillated between 31 and 106 eggs spawned per gram of female body weight.