ICES Journal of Marine Science: Journal du Conseil

Hollingworth, C. E.

doi: 10.1006/jmsc.2002.1250pmid: N/A

Carscadden, J. E.; Vilhjálmsson, H.

doi: 10.1006/jmsc.2002.1283pmid: N/A

The ICES Symposium entitled “Capelin–What Are They Good For? Biology, Management, and the Ecological Role of Capelin”, was held 23–27 July, 2001, in Reykjavík, Iceland. The co-conveners were Jim Carscadden, Canada, and Hjálmar Vilhjálmsson, Iceland, and 50 scientists from Canada, Denmark, Finland, Greenland, Iceland, Norway, Russia, the United Kingdom, and the United States registered. In this introduction, a brief overview focusing on capelin biology, the role of capelin as a forage species and commercial capelin fisheries is presented. Most of the information is gleaned from studies on Atlantic stocks, reflecting the extensive research activities initiated during the 1970s to support management of the large commercial fisheries. The 44 symposium papers were grouped into five themes: biology and ecology, multispecies interactions, abundance estimation, management, and capelin as an experimental animal. There were 17 poster presentations. Four recommendations for future activities are listed.

Vilhjálmsson, Hjálmar

doi: 10.1006/jmsc.2002.1233pmid: N/A

The stock of capelin, Mallotus villosus (Müller), that inhabits the area between Iceland, East Greenland, and the island of Jan Mayen spawns in shallow coastal water south and west of Iceland. Juveniles grow up over the continental shelf off north Iceland and off East Greenland west of the Denmark Strait. The main feeding area of adults is the Iceland Sea, the oceanic area from about 68 to 72°N, between the Jan Mayen Ridge and the East Greenland continental shelf. After the feeding season, the adult stock assembles over the outer shelf off north Iceland and migrates to the spawning grounds along the south and west coasts from December to March. The main oceanographic features of Icelandic waters and the Iceland Sea are described and capelin migrations related to the distribution of water masses and the ocean current systems in the area. In the past two decades there have been large variations in capelin migrations and catchability, especially during the feeding season. However, these variations can only be explained in part by the available environmental data. Year-class abundance appears to be determined by survival during the first winter, in tune with the greater environmental variability off north Iceland than south and west of Iceland, where these capelin spawn and the larvae start drifting. Adult growth is positively related to the flow of Atlantic water into the area north of Iceland, indicating improved feeding conditions in the Iceland Sea when the Irminger Current is strong. There can be large interannual variations in number and weight-at-age in the adult stock. The main predators are whales, seabirds, and fish, especially cod. The combined annual removal by predators is estimated to have been 2.1–3.4 million tonnes in the early 1990s. The mean weight-at-age of cod aged 5–8 years dropped by up to 25–30% when capelin abundance was low in the early 1980s and 1990s. The relatively low mean weight of cod in the past 3 years may well be due to changed distribution and migration of capelin, resulting in reduced access of cod to this most important item in their diet.

Jákupsstovu, Stein Hjalti í; Reinert, Jákup

doi: 10.1006/jmsc.2002.1245pmid: N/A

Small numbers of 0- and 1-group capelin are frequently found in Faroese waters and, because no spawning/nursery areas have been located there, their presence has been attributed to eddies from the East Icelandic Current occasionally entering the Faroe Shelf. In 1991 an exceptionally large number of 0-group capelin was caught in the 0-group research survey, and from the late 1980s to the early 1990s, several other unusual biological phenomena were identified, including low primary production, recruitment failure to major demersal fish stocks, and immigration of autumn-spawning herring. We discuss these phenomena in relation to the atypical oceanographic conditions of the period.

Friis-Rødel, Elisabeth; Kanneworff, Per

doi: 10.1006/jmsc.2002.1242pmid: N/A

The limited quantity of published and unpublished literature and historical material on capelin, Mallotus villosus (Müller), in Greenland waters is reviewed, and the information is synthesized to describe distribution, stock discrimination, migration, and life history. The biological information is compared with information from beach-spawning populations elsewhere. The role of the species as a forage fish for other organisms, stock size estimates, and the commercial and experimental fisheries are reviewed.

Nakashima, Brian S.; Taggart, Christopher T.

doi: 10.1006/jmsc.2002.1260pmid: N/A

We postulate that the variation in capelin, Mallotus villosus (Müller), egg concentration among spawning beaches in eastern Newfoundland is a function of beach characteristics. This hypothesis is explored by examining relations between egg concentration and beach characteristics among 15 beaches located around the perimeter of Conception Bay. Beaches ranged in mid-tide area from 300 to 8000 m2, in shore-normal orientation from 20 to 330°, in median grain size from 2.4 to 11.3 mm, and in egg concentration from 360 to 4380 cm−2 mid-tide zone. Variations in beach sediment grain-size distributions were captured by variations in the overall rate constant (k) and inflection point (I) of the logistic equation fitted to the cumulative percentage grain-size distributions. Beach orientation explained 57% of the variation in egg concentration among beaches. Orientation and k explained 61% and additional exploratory models explained 80–86% of the variation. Our findings build upon previous reports that describe the significance of the physical environment on the early life history of capelin and provide a quantitative method for classifying the spawning habitat of beach-spawning capelin.

Nakashima, Brian S.; Wheeler, John P.

doi: 10.1006/jmsc.2002.1261pmid: N/A

In Newfoundland, Canada, capelin, Mallotus villosus (Müller), predominantly spawn intertidally on gravel beaches, but demersal spawning in coastal waters adjacent to spawning beaches has been reported. Demersal spawning is hypothesized to occur after the completion of intertidal spawning, when beach water temperatures become too warm for spawning. We present results from a study of capelin spawning and egg development in a single major spawning location that reject this hypothesis. In 2000, some demersal spawning took place simultaneously to beach spawning, the choice of spawning location being dictated primarily by water temperature. Our results indicate that beach spawning is the preferred option. Peak spawning dates during the past decade were in July, approximately four weeks later than during the 1980s. Demersal spawning was common during the 1990s. In 2000, larval emergence from demersal spawning sites was negligible. We discuss the implications of demersal spawning to overall reproductive success when spawning is delayed.

Anderson, John T.; Dalley, Edgar L.; O'Driscoll, Richard L.

doi: 10.1006/jmsc.2002.1241pmid: N/A

Juvenile capelin, Mallotus villosus (Müller), were distributed primarily on the northern Grand Banks and secondarily along the northeast coast of Newfoundland during late summer, 1994–1999. In some years, distributions extended to coastal Labrador. Capelin were seldom observed over deep water of the northeast Newfoundland Shelf or in shallow water of the southern Grand Banks. There were large areas encompassing wide ranges of capelin densities measured by the IYGPT trawl where the acoustic system did not detect capelin. Mean growth rate of capelin from 0- to 2-group was represented by length (mm)=90.9 age (years)0.57 (r2=99%). The 1-group capelin formed discrete schools that varied significantly in fish length from 65 to 110 mm (p<0.05). Spatially, the different size groups occurred at scales of <55 km and possibly <3 km in some cases. The geographic distribution of age groups was not a simple function of cohort abundance. Capelin were distributed primarily in the middle ranges of temperature (5–8°C) and zooplankton biomass (2–4 g dry weight m−2) sampled during the surveys. It is possible that interspecific competition limits the distributions of juvenile capelin, where juvenile Arctic cod (Boreogadus saida) and sandlance (Ammodytes sp.) were abundant to the north and south respectively.

Dalley, Edgar L.; Anderson, John T.; deYoung, Brad

doi: 10.1006/jmsc.2002.1251pmid: N/A

Wind conditions during the period of larval drift of capelin are examined in relation to indices of larval drift and recruitment of the species over the five years 1982–1986 in Trinity Bay, Canada. Capelin larvae were abundant during all surveys except that of July 1985, when spawning was late as a result of cooler environmental conditions. Abundance of larvae was positively correlated with subsequent recruitment and inversely correlated with the time interval between northeasterly winds following spawning. Larval transport was mainly across (from northwest to southeast) and out of the bay, away from the spawning beaches. Larval transport itself was positively correlated with both the intensity of Ekman transport and a cumulative measure of wind-forcing in July, but it was negatively correlated with a measure of variability in wind speed and direction. The wind indices were related to measures of recruitment, but their slopes were opposite in sign to those observed between them and larval transport. There was no obvious relationship between larval transport and recruitment, i.e. transport of capelin larvae out of Trinity Bay was not a necessary requirement for successful recruitment. Our data are consistent with the hypothesis that wind-generated turbulence in the upper layers of the water column can modulate survival and recruitment.

Mowbray, Frances K.

doi: 10.1006/jmsc.2002.1259pmid: N/A

Vertical distribution patterns of capelin were examined using data from spring and autumn acoustic surveys off northeastern Newfoundland in the years 1988–2000. Until 1991, capelin typically underwent diel vertical migrations from 50 to 150 m. Since 1991, vertical migrations have been reduced or have become erratic, with capelin commonly located deeper in the water column (200+m) and closer to the seabed. Changes in vertical distribution initially coincided with the onset of a severe cold period, but distributions failed to return to normal as waters warmed. Vertical distribution was examined with regard to potential habitat-selection factors, including capelin density, water temperature, fish size, maturity stage, and proximity of predators. Of these, only fish density and predator (Atlantic cod) presence were significant. Capelin occupied more of the water column when their density was high than when it was low, and they were found farther from the seabed in areas with cod than without. Results indicate that, during the 1990s, capelin should have been able to optimize vertical distribution and feeding. This is not consistent with reports of poorer capelin condition and size-at-age in the 1990s, suggesting that vertical distributions are likely a result of changes in other factors, such as prey availability.