Iceland Scallop Research Articles

A Protein Hydrolysate Enzymatically Produced from the Industrial Waste of Processing Icelandic Scallop Chlamys islandica

Dry hydrolysate was prepared from protein-containing waste of Icelandic scallop processing by means of a proteinase complex from king crab hepatopancreas. The resulting product contains no less than 80% free amino acids and oligopeptides. Predominant are aspartic acid, leucine, isoleucine, arginine, and lysine, which account for more than 50% of the free amino acids. The potential of using the protein hydrolysate as a nutrient for microorganism cultivation is estimated. It is demonstrated that the hydrolysate can be used for growing test cultures.

Field examination of dispersion patterns of juvenile Iceland scallops (Chlamys islandica) in the northern Gulf of St Lawrence

The movement of juvenile Iceland scallops, Chlamys islandica, was quantified in an inshore bed in the Mingan Islands, northern Gulf of St Lawrence, to examine whether the size partitioning over depth in this location, increasing scallop size with depth, results from a gradual downslope movement as scallops increase in size. Scallops of 30.0-44.9 mm and 45.0-59.9 mm in shell height were collected using SCUBA, tagged, and released in the centre of two 0.4-km2 grids at 15 m in depth. After 7 d and 48 d, the net distance moved by the scallops from the release points did not vary between the two size groups but varied significantly between grids. The majority of scallops (70-94%) moved downslope and the mean movement vectors were not orientated in the direction of tidal currents, but rather towards increasing depth. The downslope movement of the scallops was possibly explained by more prolonged swimming bouts when scallops swam downslope. The results suggest that the spatial size partitioning of Iceland scallops at this location is caused by a gradual downslope movement as the scallops increase in size. This study provides the first experimental evidence supporting the controversial hypothesis of recruitment into adult scallop populations involving swimming of juveniles from nursery areas.

Size-related decrease in spatial refuge use by Iceland scallops Chlamys islandica:ontogenetic behavioural changes or decreasing refuge availability?

We examined whether the size-related shift from refuges to exposed surfaces by Iceland scallops Chlamys lslandlca In the Mlngan Islands, northeln Gulf of St Lawrence, eastern Canada, is caused by behavioural changes in their tendency to use lefuges or by decreasing refuge availability as they increase in size A laboratory expenment indicated that the frequency of refuge use did not vary with scallop size when the entrance to available refuges was sufficiently large which suggests that the tendency of scallops to use refuges does not change dunng ontogeny The size of cievices used incleased w t h scallop size, indicating that the size structure of refuges potentially could determine size-specific refuge use Our field observations using SCUBA indicated that the availability of sultably sized refuges (shells of the bivalve Splsula polynyma] decreased markedly with increasing scallop size Slze-related changes in the frequency of refuge use were positively correlated with refuge avallabil~ty suggesting that the shift from refuges to exposed surfaces is caused by decreasing availability of suitably sized refuges as scallops lncrease in size However the density of iefuges was generally greater than the density of scallops, which suggested that refuges were utllized below their carrying capacity The proport1011 of adequately slzed refuges which were occupied by scallops was low ( < l 5 %) and decreased with lncreas~ng scallop slze possibly because scallops had increasing difficulty In locatlng refuges of suitable size as they Increased in size That the shells used as refuges by scallops covered only 6 4 % of the bottom should decrease the probability of their being found Further, because the frequency of suitable refuges decreased wlth increasing scallop size, scallops should progressively have increasing difficulty in locating refuges This would llkely increase the time scallops are exposed to predators while searching for refuges, which is hkely to be cntical for small scallops glven thelr high vulnerability to predators Hence encounter rates w ~ t h refuges could potentially produce a demographic bottleneck In respect to survlval of recrults

Field evaluation of the effects of refuge use and current velocity on the growth of juvenile Iceland scallops, Chlamys islandica (O.F. Müller, 1776)

We examined whether the use of crevices to avoid predators places Iceland scallops Chlamys islandica in flow conditions which result in reduced growth. Field experiments in the Mingan Islands, northern Gulf of St. Lawrence, demonstrated that refuge use enhanced growth rates of small scallops (15–30 mm in shell height) but had no detectable effect for larger individuals (30–60 mm). Thus, use of refuges does not appear to force scallops to trade-off survival and growth opportunities as generally assumed in predation risk theory. Current velocity, as estimated from erosion rates of plaster blocks, was markedly less in refuges (≈ 0.9 cm · s −1) than on exposed surfaces (≈ 1.9 cm · s −1). Feeding efficiency of scallops generally decreases with increasing current velocity. As the velocity threshold which inhibits filtration is generally lower for small individuals, the reduced current velocity could contribute to the higher growth of small individuals in crevices.

Ontogenic habitat shifts of the Iceland scallop, Chlamys islandica (Müller, 1776), in the northern Gulf of St. Lawrence

Nous avons etudie la distribution spatiale du petoncle d'Islande, Chlamys islandica (Muller, 1776), en plongee autonome (scuba), dans une population non-exploitee de l'archipel de Mingan, dans le nord du golfe du St-Laurent. La repartition bathymetrique variait selon la taille: les petoncles 60 mm dominaient plus en profondeur (30 m). La majorite des petits petoncles se trouvaient dans des crevasses sous des coquilles de bivalves et des roches. La repartition bathymetrique selon la taille ne semblait pas decouler de mortalite differentielle entre les profondeurs. Des experiences de predation in situ ont suggere que la pression de predation sur differentes tailles de petoncles etait similaire entre les profondeurs experimentales (15 et 25 m). La vulnerabilite a la predation ainsi que l'utilisation de refuges spatiaux diminuait avec l'augmentation en taille des petoncles, suggerant un changement ontogenique de microhabitat ajuste au risque de predation. La distribution de rhodophytes, un substrat pour la fixation larvaire, expliquait en grande partie la distribution bathymetrique des recrues. La survie des recrues pourraient etre favorisee en faible profondeur (15 m) par l'abondance de coquilles de bivalves, si ces dernieres procurent un refuge contre les predateurs. Nous proposons que la repartition spatiale des differentes tailles de petoncles dans cette population est le resultat d'une fixation larvaire accrue et d'une survie superieure des recrues en faible profondeur, suivit d'un mouvement graduel vers les profondeurs avec l'augmentation en taille des petoncles.

Ontogenic habitat shifts of the Iceland scallop, &lt;I&gt;Chlamys islandica&lt;/I&gt; (Müller, 1776), in the northern Gulf of St. Lawrence

Ontogenic habitat shifts of the Iceland scallop, &lt;I&gt;Chlamys islandica&lt;/I&gt; (Müller, 1776), in the northern Gulf of St. Lawrence

Size-related changes in vulnerability to predators and spatial refuge use by juvenile Iceland scallops Chlamys islandica

Size-related changes in vulnerability to predators and spatial refuge use by juvenile Iceland scallops Chlamys islandica

Short-term variations in settlement and early spat mortality of Iceland scallop, Chlamys islandica (O.F. Müller)

A field experiment was carried out from 20 September to 9 November 1992 in the Baie des Chaleurs (Gulf of St. Lawrence) to examine the temporal pattern of Iceland scallop ( Chlamys islandica) spat settlement on artificial filamentous collectors. One hundred sixty five cubic Vexar cages (10 × 10 × 10 cm) filled with 150 g (wet weight) of dead hydroids ( Tubularia larynx) perisarcs were deployed and retrieved using a sequential time exposure schedule [collectors were deployed in decreasing numbers (30 to 5) every ≈ 5 days and retrieved in the reverse order (5 to 30) of their immersion]. This approach gave independent samples with respect to time and made it possible to estimate (1) near instantaneous settlement density, (2) short-term post-settlement mortality, (3) cumulative collection efficiency, and to compare (4) settlement onto substrata immersed for different periods of time. Simultaneous measurement of environmental factors (tidal range, current speed, seawater temperature and salinity) allowed an assessment of the relative influence of environmental factors in determining settlement density. The spat collectors used in this study were successful in collecting many thousands of Iceland scallop post-larvae. Settlement took place during 1 month, from the middle of September to the middle of October 1992 and collectors immersed for 10, 15, and 20 days collected significantly more spat than those immersed for 5 days. After the settlement season, spat mortality remained low for at least an additional 25 days (the end of the observation period). The daily mean density (DMD) of newly settled spat during each ≈ 5-day interval varied significantly in time and there was no significant correlation between DMD and the environmental factors. Different hypotheses concerning larval flux (no. of larvae × mean current speed) and their probability of coming into contact and being retained by a collector (retention efficiency) are proposed to explain the temporal pattern of spat collection observed in this study. Some suggestions are made to enhance collection efficiency of artificial scallop spat collectors.

Population Parameters of the Iceland Scallop (Chlamysislandica(Mäller)) from West Greenland

New information is presented on the distribution, size composition, sex ratio, maturity and growth of the Icelandic scallop (Chlamys islandica) along West Greenland. In West Greenland, populations of C. islandica are mainly distributed in the outer regions of fjords at depths between 20–60 m. They are distributed in areas characterized by strong tidal currents and populations are generally composed of large scallops in the range of 60–110 mm shell height with the majority being 75–100 mm. There is minor morphometric variation between areas. The sex ratio is generally 1:1 and they become sexually mature from 30 to 55 mm shell height at ages 4–9 years. There are small differences in shell height-at-age between males and females, but between area means vary from 58 to 68 mm at age 10 years. Seasonal and areal variations in both the muscle and gonad weights were also observed.

The Iceland scallop, Chlamys islandica (O.F Müller), in Breidafjördur, west Iceland. III. Growth in suspended culture

During two years, from September 1989 to September 1991, a study was carried out to evaluate the potential of pearl net cultivation of Iceland scallop, Chlamys islandica (O.F Müller), in Breidafjördur, west Iceland. In September 1989 1-year-old spat (mean height 9.8 mm±2.0 s.d.) were transferred from collectors to pearl nets suspended from flotation at 6–8 m depth. Shell increment, chlorophyll- a, temperature and salinity were monitored each month at the experimental site. During the second year in the pearl net culture, growth of soft parts of the body was also measured. By September 1990 the scallops had an average shell height of 24.6 mm±6.0 s.d. and in September 1991, three years after settlement, a height of 43 mm±8.3 s.d. was reached. Growth rate was related to food availability (measured as chlorophyll- a). During both years of the investigation height-specific growth rate reached a maximum (0.7% day −1 and 0.3% day −1, respectively) in early spring and again in summer, but it gradually decreased as the scallops grew older. The growth season lasted from March to October during both years of investigation. The results showed that the growth of Iceland scallops can be increased markedly by suspending the animals in hanging culture in more favourable environmental conditions than found on the natural scallop beds. The feasibility of cultivating Chlamys islandica in Breidafjördur is discussed.

Settlement of Iceland scallop Chlamys islandica spat in response to hydroids and filamentous red algae: field observations and laboratory experiments

Sampling carned out in the Baie des Chaleurs (Gulf of St. Lawrence, Canada) in 1990 and 1991 showed that newly settled Iceland scallop Chlamys islandica spat were not randomly distributed on the sea bottom. Various inorganic (sand, gravel, pebbles, shells of different species) and organic (algae and animals) substrata were examined. Twenty times more post-larvae were found on pensarcs of the dead hydroid Tubulana larynx than on hve hydroids and red algae (another preferred natural substratum). Maximum densities, up to 300 spat g' (dry wt) of hydroids, were observed on a mooring line at 2 m from the bottom. Laboratory expenments carried out to determine whether attachment behaviour of post-larvae could contribute to the observed distribution of spat showed that: (1) spat can resettle easily when dislodged from their substratum; (2) independent of their origin, over 60 % spat preferred to resettle on dead rather than live hydroids, filamentous red algae (Ptilota serrata and Phycodrys rubens) or fishing line (used as control); and (3) they also preferred to resettle on the type of substratum to which they were previously attached. Different hypotheses concerning active and passive larval settlement processes and post-larval redispersion strategy are proposed to explain this relationship between scallops and hydroids.

Allozymic variability in the Iceland scallop Chlamys islandica: geographic variation and lack of growth-heterozygosity correlations

Populations of the Iceland scallop Chlamys islandca from the waters off Jan Mayen, Spitsbergen, Bear Island and northern Norway were inveshgated for allelic variation at 6 polymorphic gene loci. The 3 loci encoding for glucose phosphate isomerase (GPI), phosphoglucornutase (PGM) and superoxide dismutase (SOD) substantiated earlier findings of exceptionally high polyrnorphism at these loci in the Iceland scallop, higher than for many other pectinids. Loci encoding for malate dehydrogenase (MDH) and leucine-arninopeptidase (LAP) also exhibited higher polymorphism than is known for other pectinids. The high variability at an increasing number of enzyme coding loci for the subarctic/arctic species appears to contrast with predictions of negative correlations between environmental homogeneity and gene polymorphism. Allele frequencies at Mdh. Pgrn and Sod varied between populations over the geographical range surveyed, giving supportive evidence of at least partial geographic isolation between stocks. Data of the present study do not provide evidence that multiple-locus or single-locus heterozygosity affect longevity of C. islandica. Heterozygosity did not increase with age of the scallops, nor were positive growth-heterozygosity correlations demonstrated, either at singlelocus or multiple-locus heterozygosity. This contrasts with findings for several other bivalves, but is in accordance with observations for other pectinids.

The Iceland scallop, Chlamys islandica (O.F. Müller) in Breidafjördur, west Iceland. I. Spat collection and growth during the first year

Spat of the Iceland scallop Chlamys islandica (O.F. Müler), was artificially collected, using onion bags of 6 mm mesh size filled with monofilament of 0.4 mm, and polyethylene bags of 4.5 mm mesh size filled with monofilament of 0.2 mm. The spat collectors were placed at 25–35 m depth in Breidafjördur on the west coast of Iceland, in the middle of July 1988. The settlement of the spat was observed in the middle of September. No significant difference was found in the settlement at different depths but it varied greatly according to the diameter of the monofilament in the bags. Heaviest settlement was observed on the thinner monofilament (0.2 mm). The instantaneous growth rate was highest from the middle of September to the middle of October (3.6%/day) but decreased during the winter. In May the growth increased again concurring with an observed increase in sea temperature and abundance of phytoplankton. In September 1989, 1 year after settlement, the spat had reached an average size of 9.8 mm. Some evidence of secondary migration was observed for Chlamys islandica 1 year after settlement.

Genetic differentiation of the Iceland scallop Chlamys islandica (Pectinidae) in the northern Atlantic Ocean

Allozymic variation at gene loci encoding for glucosephosphate isomerase, phosphoglucomutase and superoxide dismutase was investigated In populations of Chlarnys islandica from waters around Jan Mayen, Spitsbergen, Bear Island and northern Norway. The Gpi locus was particularly polymorphic with at least 12 different alleles and a mean heterozygosity of 84 % Half the individuals were heterozygous at Pgm-2 and between 30 and 40 % at Sod. The high polymorphism at Gpi runs counter to an earlier hypothesis suggesting a positive correlation between environmental variability and Gpi polymorphism of pectinids. Pgm-2 and Sod revealed significant allele frequency heterogeneity among the different areas, Gpi only when the effective number of alleles was considered. The species has a large dispersal potential during a long planktonic larval stage, but information on the surface current system in the North Atlant~c suggests that restr~cted gene flow, with possible contributions from selective constraints, account for the observed pattern in gene variability. It is suggested that the conservative approach of managing each area as if it contained discrete genetic units of the species should be adopted.

Efficiency of Meat Recovery from Iceland Scallops (Chlamys islandica) and Sea Scallops (Placopecten magellanicus) in the Canadian Offshore Fishery

The process of removing adductor muscles (meat) through manual shucking of Iceland scallops and sea scallops at sea results in loss of meat yield to the fishing industry. In the study of Iceland scallops, this loss was negatively correlated with shell size and decreased from about 30% at 60 mm (shell height) to 11% at 90 mm, with an average loss of 23%. Meat recovery was somewhat more efficient from sea scallops, but paradoxically the loss in yield increased slightly with shell size from 8% at 60 mm to 10% at 90 mm. The average loss for commercial-sized sea scallops (~100 mm) was estimated to be 11%. In addition to such factors as experience, speed and shucking habits of the fishermen, relative efficiency of meat extraction from the shells of the two species appears to be related to shell size, tenacity of shell closure and shell morphology (curvature).

Notes on Norwegian marine Amphipoda. 9. Aristias megalops Sars, 1895 (Lysianassoidea) rediscovered

The Lysianassoid amphipod Aristias megalops Sars, 1895 previously only known from the type-specimens, is recorded from western and northern Norway. In the Tromsø area the species lives in association with an unidentified sponge on the valves of the Iceland scallop Chlamys islandica (O.F. Müller).

The significance of various environmental parameters for growth of the Iceland scallop, Chlamys islandica (Pectinidae), in hanging culture

Iceland scallops, Chlamys islandica (O.F. Müller), were grown in hanging culture at 3 different depths (2, 12 and 40 m below the sea surface) in a northern Norwegian fjord. The growth of the soft parts of the body and the shell increment were monitored throughout the growing season (March until September). At the same time, temperature, salinity, water density, current speed, chlorophyll, particulate organic matter (POM) and particulate inorganic matter (PIM) were monitored at each of the experimental depths. Analysis of the environmental data together with the growth data showed that growth differences between the experimental depths were essentially the results of differences in nutritional conditions for the scallops, defined by the relationship between PIM and POM in the water column. The results also showed that growth in Iceland scallops can be increased significantly by suspending the animals in a more favourable nutritional environment than that found on the natural scallop beds.

Growth variation with age and water depth in the Iceland scallop ( Chlamys islandica, Pectinidae)

Mature and immature Iceland scallops; Chlamys islandica, were allowed to grow undisturbed from June until December in hanging containers placed 2 m, 7 m, 12 m, 20 m and 30 m from the sea surface in a northern Norwegian fjord. All the immature scallops increased in shell size while only some of the mature animals did so. Culture depth influenced the amount of shell increment in all groups. Depth also affected growth of soft parts in the immature animals, 12 m depth being the most favourable for growth. These observations are discussed in relation to the growth season for this species.

Seasonal variations in gamete development in the Iceland scallop, Chlamys islandica

Annual cycles of development were studied in male and female Iceland scallops (Chlamys islandica). Volume fractions of each germ cell type and other gonadal tissue were determined by histological and stereological techniques. Spawning occurs during a short period in late June and early July.

The culture of the Iceland scallop, Chlamys islandica (O.F. Müller) : I. Spat collection and growth during the first year

Spat of the Iceland scallop, Chlamys islandica (O.F. Müller), was artificially collected using thin nylon monofilament as a substrate for settlement. Collectors placed at depths between 15 m and 40 m in Balsfjord, north Norway, collected most spat at depths of between 30 m and 40 m. After settlement in September the spat grew slowly until the following spring (April/May) when growth accelerated. One year after settlement a shell height of about 7 mm was attained. There was also some evidence that secondary migration in this species begins about 1 year after settlement.