ALBERT

Description: Major- and trace-element as well as Pb-isotope data are presented for greenschist- to amphibolite-facies greenstones from two locations: (1) metabasalt-breccias from the Galfipagos Rift at 100°W; and (2) metabasalt-breccias and unbrecciated greenstones from the Chile Ridge at 38°S. Greenstone-breccias from both locations display stockwork-like sulfide mineralizations related to the upflow portion of a hydrothermal convection system. Whereas Galfipagos Rift stockwork sulfides belong to the "normal" type containing Cu-Fe-sulfides, Chile Ridge stockwork sulfides are galena-rich Pb-Zn _ Cu-sulfides and represent a previously unknown type of sulfide mineralisation in a MORB environment. Geochemically, the greenstones can be divided into two types: (1) The unbrecciated galena-free greenstones from both Chile Ridge and Galfipagos Rift show at least a 10-20-fold Pb enrichment compared to fresh MORB. With respect to similar Pb enrichment measured in greenstones from two other locations, i.e. DSDP Hole 504B and Galfipagos Rift near 86°W, we suggest that this may be a general feature of all stockwork-mineralised oceanic greenstones. (2) The galena- and quartz-rich metabasalt-breccias from the Chile Ridge are up to 3000-fold enriched in Pb (up to 1000 Ixg/g Pb in the whole-rock analyses) compared to MORB and indicate Pb mineralisation two orders of magnitude higher than that of the "normal" greenstone-type. A mass-balance calculation carried out using crustal column thickness of 3000 m with a 200-m-thick greenstone layer and 0.15 m of galena-beating breccias shows that at the Chile Ridge ~ 42% of the entire Pb is concentrated in the greenstones. This suggests that the rest of the crustal column is depleted in 58% of its primary Pb content. This degree of depletion matches well with previous calculations that a 56% depletion of Pb in oceanic crust subjected to mantle-recycling via subduction would be necessary to yield a HIMU mantle source within 2 Ga. Despite the need for future investigations into the extent and volume of the Pb enrichment in Chile Ridge greenstones, we believe that this process of major Pb redistribution is capable of creating huge volumes of oceanic crust that on average are extremely Pb-depleted and which when recycled would produce the HIMU source. Keywords: Chile Ridge; Galfipagos Ridge; Hydrothermal alteration; Greenstones; Geochemistry; Mineralogy

Description: A standard, universally useful classification scheme for deepwater habitats needs to be established so that descriptions of these habitats can be accurately and efficiently applied among scientific disciplines. In recent years many marine benthic habitats in deep water have been described using geophysical and biological data. These descriptions can vary from one investigator to another, which makes it difficult to compare habitats and associated biological assemblages among geographic regions. Using geophysical data collected with a variety of remote sensor systems and in situ biological and geologic observations, we have constructed a classification scheme that can be used in describing marine benthic habitats in deep water.

Description: A structural model encompassing the southern North Sea basin west of the Central Graben has been developed. This model consists of a rift system affecting the post-salt section around the basin margin and a large area of detached compressional buckle folds within the basin. This pattern is initially a response to gravity sliding of the post-salt section on the salt within the basin during the late Triassic to late Jurassic. A close relationship between the location and trend of the peripheral graben system and basement structures in the pre-salt is noted. Pre-Jurassic extension across the peripheral graben systems was balanced by the sum of fault heaves at the pre-salt (Rotliegend) level and shortening across salt-cored buckle folds in the post-salt section. Salt pillows and swells passively infilled the cores of these gravity-induced buckle folds. Cretaceous and Tertiary inversion involved basin tilt and renewed movement on basin-bounding basement faults; notably, reverse movements did not propagate from basement structures up into the peripheral graben systems. The post-salt sedimentary section experienced gravity spreading in response to inversion-related uplift, resulting in syn-inversion extensional faulting in the Sole Pit High, where the Mesozoic section was thickest. This extension, combined with a loss of fault heave in the pre-salt section, was balanced by amplification of salt-cored buckle folds in the centre of the basin. In the context of the model described here, salt pillows represent passive infill of thin-skinned, compressional buckle folds which later amplified during thick-skinned basement shortening. Crestal collapse of such folds occurs via normal faulting, accompanied by reactive diapirism. Such reactive diapirs establish conduits through which salt may leak, leading to pillow deflation and ultimately conduit preservation as a salt wall (flanked by rim synclines in areas where the buckle folds were emergent). The salt structures described here are related to cover folds and faults, which in turn reflect episodes of basin extension, tilting and inversion. Hence individual salt structures can be said to be only remotely connected with regional, intraplate stresses.

Description: Normal faulting and halokinesis have been important controls on the deposition and subsequent deformation of Mesozoic and Tertiary strata in the North Sea. In addition to the previously documented mechanisms of salt withdrawal, dissolution and differential sedimentary loading, it is recognized that gravity-driven thin-skinned extension above inclined salt layers has played an important part in North Sea basin development. Commercial section restoration software has been used to facilitate depth conversion, restoration and decompaction of seismic sections selected from an interpreted regional database in the western central North Sea, allowing validation of the interpretations, and a graphical and highly quantitative description of salt-assisted extension. Results of this work show that Zechstein Group evaporites were deposited in shallow sag basins during the Permian. Triassic sedimentary pods were generated by localized deposition in synclinal basins and grabens above the evaporites. Bedded salt became folded, while mobile salt flowed to fill anticline cores. Since the early Jurassic, regional tectonic tilting related to post-rift subsidence and increasing sedimentary overburden have caused allochthonous Mesozoic and Tertiary strata to extend by gravity spreading above the mobile salt layer, which detaches the allochthon from the underlying autochthonous Late Palaeozoic rocks. Concave-up listric normal faults sole out in the salt layer, propagate into the overlying cover sewuence, and have been active at different geological times causing stratal thickening and folding within the allochthon. Antithetic and synthetic normal faults have developed, producing complex upward branching fault systems. In map view, the listric faults form curvilinear en echelon arrays, the faults linked by relay ramps. Fault blocks are typically 3–7 km wide, 2–3 km thick and 7–10 km long. Salt movement during the Jurassic-Tertiary has been driven by active extension of the cover, causing salt to fill potential voids created by fault block rotation. Thus salt highs occur beneath sites of extension. The listric faults generally dip in the same direction as the sub-salt surface, although there are also some major counter-regional faults. During extension, regional dips have increased up to about 5, which is sufficient for gravity-driven extension above a salt layer. A total extension of about 6% has occurred. The gravity-driven thin-skinned extension documented in the western central North Sea is a phenomenon which can be recognized elsewhere in the North Sea basin, and can be readily compared with similar phenomena already documented in offshore Angola, Brazil, Nova Scotia and the Gulf of Mexico.

Description: Temperature and ration level can differentially affect growth and life history characteristics of marine organisms. In this experiment we reared juvenile cuttlefish, Sepia elliptica, under two feeding regimes (satiation and half satiation) and two temperature regimes (25 and 30°C). This study examined differences in somatic growth, muscle tissue structure and composition as a function of temperature and food levels. We estimated body mass and the concentration of water, carbohydrate, protein and lipid in the mantle muscle tissue for each individual. Both high water temperature and high feeding rations increased growth rates. Temperature appeared to change the rates of muscle fibre generation and fibre growth similarly. In contrast, the ration level altered the relative rates of fibre production and fibre growth. The muscle tissue of individuals reared at 30°C had higher concentrations of carbohydrate and protein. In contrast, increasing ration levels only increased carbohydrate concentrations in the muscle tissue. The muscle tissue of reared juveniles had lower concentrations of carbohydrate and protein than wild individuals of similar size. In conclusion, water temperature and feeding levels both affect somatic growth, but the nature of the effect at the sub-organismal level differs.

Description: Distribution of elements in statoliths of squid Loligo vulgaris reynaudii d'Orbigny, 1845 was studied, using the true elemental imaging system (Dynamic Analysis) of the NAC nuclear microprobe. The analysis revealed various patterns of Ca and Sr distributions. The biological interpretation of the most frequent pattern is linked with the role of Sr in the statolith deposition process. Other patterns are linked with the technique used and the specific characteristics of the sample. Traces of other elements (Cr, Mn, Fe, Cu, Zn, Br, Pb) were also found. Likewise, their presence may have the biological interpretation (Zn, Cu and Br), or is an artefact linked to the methods and conditions of sample preparation and/or analysis. Methodical aspects of using proton backscattering for PIXE X-ray yield corrections are also discussed.

Description: We have determined the content of free l-amino acids and d-aspartate in the nervous tissue of three representative cephalopods: Sepia officinalis, Octopus vulgaris, and Loligo vulgaris, and the optic lobes of adult and embryo Sepia officinalis. Taurine is the most abundant amino acid in the cephalopod nervous tissue. Its content amounts to more than 50% of the total free amino acids. The other most concentrated amino acids are Glu, Ala, Asp, and GABA. High concentrations of d-aspartate were found in the nervous tissue of all cephalopods examined (7–12 μmol/g wet tissue) which represents 50–80% of the total aspartate (d + l), depending on the animal. Among the various regions of the brain of Octopus vulgaris, d-aspartate was found to be evenly distributed in the various regions of the brain. In nerve tissue of Sepia officinalis, there is no significant difference in the pattern of free l-amino acids, in particular of the d-aspartate concentration, between adults and embryos, except for GABA, Gly, His and Thr. This suggests that d-aspartate in nerve tissue of the Cephalopoda is of endogenous origin and not a product of accumulation from exogenous sources. From a comparative study of the content of d-aspartate in the nervous tissue of different animals, we found that protostomia contain a significantly higher amount than deuterostomia. Thus, d-aspartate could be a criterion to distinguish the protostomia phyla from the deuterostomia phyla.

Description: Three hundred and fifty individuals of 12 species of cephalopods which differed in their feeding habitats were sampled from the French Atlantic coast to the sub-Arctic region (Bay of Biscay, English Channel, west Irish coast and Faroe Islands) and analysed for their cadmium contents. Comparison of the Cd levels of the cephalopods showed that those from the sub-Arctic area contained very high Cd concentrations compared to those from lower latitudes such as along the French Atlantic coast. High Cd levels in cephalopods from the sub-Arctic zone correspond closely to the reported high Cd concentrations in the tissues of top vertebrate predators from the same area. Comparison of the weekly Cd intakes for the Faroe Island pilot whales with the `Provisional Tolerable Weekly Intake' for humans recommended by the World Health Organisation, showed that top vertebrate predators are often subjected to Cd doses far in excess of those recommended for humans. Our limited survey results suggest that cephalopods constitute an important source of Cd for cephalopod predators, and that this bioaccumulation effect is most evident at high latitudes.

Description: Basic biological parameters of cuttlefish, Sepia officinalis, in the English Channel are described from samples of commercial and research vessel landings made between April 1994 and September 1995. There was a significant difference between the length–weight relationship of male and female cuttlefish. Growth of both sexes was rapid and seasonal during the last 12 months of life. Males grew faster than females, and reached larger overall lengths and weights. Most males reached maturity before the start of their second winter, although the testis continued to develop until spawning took place the following spring. Female maturation began later and was more prolonged such that it was completed towards the end of the second winter. Adults of both sexes spawned after the second winter between late March and July. Commercial landings data showed spawning cuttlefish initially arrived on inshore grounds in the western Channel, but slightly later and in greater numbers on the inshore grounds of the middle and eastern Channel. The weight and value of cuttlefish landings made by UK vessels in the Channel increased greatly between the mid 1980s and the mid 1990s such that cuttlefish are now a major part of the earnings for several fisheries. The most important fisheries were the offshore beam trawls, and inshore otter trawls and nets. The exploitation pattern of each fishery is described from quarterly samples of commercial landings taken between April 1994 and March 1996. Each exploitation pattern is shown to be a function of the region fished, the catching gear employed, and the growth and migrations of the cuttlefish population. Some implications for stock management are discussed.

Description: The use of marine parasites as non-intrusive natural tags of their hosts was first broadly applied in fisheries science in the 1940s. Both micro- and macroparasites have been used to assess the status of current stocks of several commercially exploited species of marine animals. Here, Santiago Pascual and Eric Hochberg offer a brief comment on marine parasite tags as a stock assessment methodology, with special reference to cephalopod hosts.

Description: Laboratory rearing of 19 Octopus mimus from 40 to 589 g at 20.1±1.8°C (September to December 1991) provided information on the growth pattern and variation in instantaneous relative growth rate (G) of this Chilean littoral octopus. The three smallest specimens (ranging from 40 to 49.8 g) attained an average weight of 558 g in 70 days. Growth of this species had two phases. Growth was exponential during the first 40 days of culture with an average G of 5.33%. It slowed and became logarithmic when the animals attained weights ranging from 326.6 to 439 g. Instantaneous relative growth rate decreased from 2.25% to 0.99% during the logarithmic phase. A similar pattern was found for the 16 larger specimens (61.4–406.4 g initial weight). The change in growth pattern observed between the exponential and logarithmic phases occurred at body weights ranging from 326.6 to 454.2 g. No differences in growth were found between sexes in O. mimus. The growth pattern of this species is discussed and compared to other small-egged octopus species raised in captivity.

Description: Cephalopods are highly visual animals; the importance of chemical perception to these complex mollusks is less well understood. In this experiment, ventilation rate was used to measure the perception of chemical stimuli by cultured juvenile cuttlefish. The test tank had opaque sides and top to visually isolate the cuttlefish. A clear bottom permitted direct observation of funnel movements associated with ventilation. Cuttlefish cannot see beneath them when resting on the bottom; trials began once cuttlefish had remained calmly on the bottom for at least 15 min. The chemical stimulus was placed in a tank located upstream from the test tank containing a single cuttlefish; the cuttlefish's ventilation cycles were measured by direct observation. Ventilation rate increased significantly after exposure to ink from a conspecific, water containing food, water containing a conspecific, novel seawater and water that had contained sea turtles, potential predators. Results were obtained despite any background chemicals remaining within the closed sea water system, suggesting findings are probably robust to the conditions cuttlefish would normally experience in the ocean. Results are consistent with those obtained using visual stimuli and extend previous research indicating that cephalopods are capable of using chemical cues to detect salient environmental features.

Description: A total of 6171 specimens of Octopus mimus was collected from the commercial small-scale fishery in northern Chilean waters (off Iquique) between January 1991 and March 1992. The animals were grouped by sex, size and month for modal progression analysis (MPA). Total length of the animals ranged from 24 (66 g) to 107 cm (4358 g) for males and from 28 (63 g) to 115 cm (3714 g) for females. There were no significant differences in the length–weight relationship between sexes except in summer. The size structure of the exploited population of O. mimus is rather complex and MPA indicated six sub-annual cohorts for males and five for females. Instantaneous relative growth rate (G) in total body weight varied from 0.29% to 1.37% d−1 and from 0.23% to 1.78% d−1 for males and females, respectively. Seasonality and water temperature affected G in both sexes. Differences in G among sub-annual cohorts within the same season were found and it was observed that G tended to decrease with size.

Description: Large numbers of seabirds are killed each year within the Australian Fishing Zone (AFZ) by Japanese longline vessels targeting tuna. In recent years the estimated rate of seabird bycatch in the AFZ has been in the order of 0.15 birds/1000 hooks, translating to mortalities of 1000–3500 birds per year. These estimates are absolute minima because not all birds killed remain on hooks to be observed hauled aboard the vessels. The observed seabird catch rate varies annually, seasonally and spatially. Most birds are killed: (a) during the summer fishing season (October to March), even though most fishing effort occurs in winter; (b) when longlines are set during the day; (c) in the waters around southern Australia. Uncertainties in the observed catch rates prevent confident assessment of trends, but seabird catch rates do not appear to be showing a sustained decrease. The process of the incidental collection of seabird bycatch data (by observers whose priority is to fish sampling tasks) renders the seabird bycatch data inadequate for reliable assessment of trends in total numbers of birds killed over time. Sixteen seabird species of birds killed on longlines in the AFZ have been identified. These include black-browed (Diomedea melanophris), shy (D. cauta), grey-headed (D. chrysostoma), yellow-nosed (D. chlororhynchos) and wandering albatrosses (D. exulans), flesh-footed shearwaters (Puffinus carneipes) and white-chinned petrels (Procellaria aequinoctialis). Seventy-four per cent of birds killed were albatrosses and the species composition of the bycatch varied with seasons and areas. Most species of birds killed were characterised by unequal representation of sex and age cohorts, and these unequal representations were not consistent between fishing grounds or seasons.

Description: NA and protein concentrations, and the RNA to protein ratio, were measured in four species of cephalopods, to evaluate sources of variation and the potential for using RNA concentration and the RNA to protein ratio as growth indices. In field samples of Loligo forbesi and Eledone cirrhosa, RNA concentrations and the RNA to protein ratio were higher in immature animals than in mature animals. In Loligo forbesi, values were also higher in males than in females and higher in smaller individuals than in large individuals. Both these trends are consistent with expected differences in growth rate, i.e. RNA is higher in faster growing animals. Mature female Eledone cirrhosa, a species in which the female is larger and presumably grows faster, had higher RNA concentrations than mature males. However, no such difference between the sexes was seen for immature E. cirrhosa or Todarodes sagittatus. Methods for transport and maintenance of Loligo forbesi in captivity in the Azores are described. Many of the captive squid showed poor growth and survival but results from these animals nevertheless confirmed that RNA concentrations were higher in males than in females and higher in animals with smaller gonads than in animals with large gonads. Higher protein concentrations were found in males than in females, and protein concentration was also positively correlated with feeding rate and digestive gland indices. Octopus vulgaris held in captivity grew rapidly and consistently and RNA concentrations were lower in bigger animals than in smaller animals. Neither experiment provided direct support for the hypothesis that RNA concentration or the RNA to protein ratio is directly related to growth rate. Systematic variation in protein concentration, e.g. in relation to recent feeding, leads us to suggest that protein concentration (mg/g fresh body weight) is likely to provide a more reliable index than the RNA to protein ratio.

Description: This review is based on the author's own data and all available published data (mostly Russian and Japanese) on the ecology, biogeography and role in the ecosystem of gonatid squids in the northern North Pacific. For the best studied species, Berryteuthis magister, information is given on size, horizontal and vertical distribution, diel and ontogenetic vertical migrations, maturation, mating, spawning, fecundity, population structure, age, growth, life cycle, horizontal migrations, underwater behaviour, food and feeding, and predators. The assessed biomass and its interannual dynamics and the fisheries importance are also covered. For other, less studied, species of the genera Berryteuthis (B. anonychus), Gonatopsis (three species) and Gonatus (seven species) all available ecological and biogeographical data are included. All species are compared according to their size, horizontal and vertical distribution, spawning habitats, diel vertical migrations and gelatinous degeneration associated with maturation. The “ecological individuality” of each species is evaluated. It is shown that each occupies its own ecological niche but these niches overlap to different degrees. The history of niche divergence in North Pacific gonatids during the Neogene-Pleistocene period is briefly reviewed. Common features are described of the horizontal and vertical distribution, relative abundance and biomass of North Pacific gonatids in general. Their roles in the ecosystem, as predators, prey, competitors and hosts of parasites is evaluated. The total biomass of gonatid squids in the whole subarctic North Pacific and the Russian Far Eastern seas is estimated as approximately 15–20 million t. They contribute some 10–15% of the total production of mesopelagic cephalopods in the World Ocean. Their yearly food consumption is assessed at 100–200 million t. The life cycle of gonatids is shorter and their P/B-coefficient much higher than that of subarctic mesopelagic fishes. As a result, though the squid biomass (calculations for the Okhotsk Sea) is less than 10% of the total mesopelagic fish and squid population, they form 58–67% of annual total fish and squid production. Thus gonatid squids have an important place in the ecosystem of the northern North Pacific and the Far Eastern seas of Russia.

Description: Some aspects of the biology and fishery of Octopus vulgaris caught by trawlers in the Balearic Sea (Western Mediterranean) are studied. The analysis of the size–frequency distribution followed the growth of specimens from January (6–7 cm ML) to August (11–12 cm ML). The sex ratio was estimated for each season and it was not significantly different from 1 : 1 in any of them. The stomach contents revealed that the octopus fed predominantly on crustaceans and fishes. Another octopus species, Eledone moschata, is present in this fishery but its catches were clearly lower than those of O. vulgaris. The analysis of the importance of these two species in relation to the rest of the commercial catch showed that octopuses represent between 20–40% of the total catch for trawlers. The highest catch rates (kg/h) were obtained in spring and at the beginning of summer. Time-series analysis of monthly catches from January 1981 to August 1996 showed two main oscillations. The lower one, with a periodicity of 12 months, reflects the annual biological cycle of the species; on the other hand, the higher one has a periodicity of 92 months, the time series available being too short to confirm the significance of this period.

Description: This paper presents data on the diet of the squid, Loligo vulgaris (Lamarck, 1799) from the south coast of Portugal (Algarve) and from the Saharan Bank (Central-East Atlantic). A total of 964 squid was collected from the Algarve coast, between March 1993 and October 1994, from bottom trawling. An additional sample of 70 stomachs was obtained in the Algarve coast from the hand jigging fishery during 1991 and 1992. In the Saharan Bank, 848 squid were obtained, between June 1993 and January 1994, with bottom trawling. Stomachs with contents for trawled squid from the Algarve coast, and the Saharan Bank represented 28.1% and 40.8%, respectively. Fish was always the main component of the diet in both regions, representing 88.6% of the total weight of the prey found in the stomachs, for the Algarve coast, and 70.9% for the Saharan Bank. The occurrence percentage and the percentage in number indicated that Trachurus trachurus and fish belonging to the family Gobiidae were the most frequent fish found in the Algarve samples, while flatfish were the most common fish in the Saharan Bank samples. Loligo vulgaris was the dominant cephalopod found in the stomachs for both regions. No differences in the diet were found between males and females. The comparison between immature and mature squid showed that the importance of fish was higher in mature squid, for both regions. The squid captured from the Algarve coast by bottom trawling (at greater depths and offshore) fed primarily on fish, while those captured with hand jigging (inshore, at lower depths) contained an important percentage of crustaceans.

Description: Male cuttlefish adopt a specific body pattern during agonistic behaviour called the Intense Zebra Display. Some components of the Display were variable, especially the chromatic component termed ‘dark face’, which could vary in the degree of darkness. Facial darkness was measured using a video analysis system. Males that eventually withdrew from conspecifics without fighting maintained a lighter face during the initial stage of agonistic encounters. When both males maintained dark faces, physical contact and fighting ensued. Therefore facial darkness could be used to predict which male–male encounters would escalate to physical contact. The strong correlation between facial darkness and subsequent behaviour suggested that males were signalling their agonistic motivation at the early stages of the encounter, which is contrary to what would be predicted from a traditional game theory analysis. It is proposed that males signal intent because the Intense Zebra Display simultaneously serves two functions: (1) it identifies the signaller as male, thus preventing unwanted copulations from other males, and (2) it functions as part of the agonistic behavioural repertoire. By using a modified (i.e. lighter-faced) version of the Display, males may be able to signal their sex, but without inducing another male to attack. In cases in which agonistic displays perform more than one function, signalling intent (i.e. signalling its likely subsequent behaviour) can be an evolutionarily stable strategy.