Capelin Mallotus Villosus Research Articles

Assessing the nutritional stress hypothesis: relative influence of diet quantity and quality on seabird productivity

Food availability comprises a complex interaction of factors that integrates abundance, taxonomic composition, accessibility, and quality of the prey base. The relationship between food availability and reproductive performance can be assessed via the nutritional stress (NSH) and junk- food (JFH) hypotheses. With respect to reproductive success, NSH posits that a deficiency in any of the aforementioned metrics can have a deleterious effect on a population via poor reproductive suc- cess. JFH, a component of NSH, posits specifically that it is a decline in the quality of food (i.e. energy density and lipid content) that leads to poor reproductive success. We assessed each in relation to reproductive success in a piscivorous seabird, the black-legged kittiwake Rissa tridactyla. We mea- sured productivity, taxonomic composition, frequency, size, and quality of meals delivered to nestlings from 1996 to 1999 at 6 colonies in Alaska, USA, 3 each in Prince William Sound and Lower Cook Inlet. Productivity varied widely among colony-years. Pacific herring Clupea pallasi, sand lance Ammodytes hexapterus, and capelin Mallotus villosus comprised ca. 80% of the diet among colony- years, and each was characterized by relatively high energy density. Diet quality for kittiwakes in this region therefore remained uniformly high during this study. Meal delivery rate and meal size were quite variable among colony-years, however, and best explained the variability in productivity. Par- ent kittiwakes appeared to select prey that were energy dense and that maximized the biomass pro- visioned to broods. While these results fail to support JFH, they do provide substantial support for NSH.

Shrinkage correction and length conversion equations for Theragra chalcogramma, Mallotus villosus and Thaleichthys pacificus

Preservation of walleye pollock Theragra chalcogramma, capelin Mallotus villosus and eulachon Thaleichthys pacificus by freezing decreased fork length (LF) up to 1·8, 5·6 and 2·7% and reduced mass by up to 8·4, 3·5 and 1·1%, respectively. Shrinkage of walleye pollock standard length (LS) was greater for fish in 95% ethanol v. 5% formalin and for fish in 10% formalin v. frozen. Equations describing the shrinkage and loss in mass for these species are presented as well as conversions between different length measurements (LS, LF and total length, LT) for fishes that were frozen.

Seasonal growth of Atlantic cod: effects of temperature, feeding and reproduction

Growth of 2659 Atlantic cod Gadus morhua aged 4 to 9 years examined in Placentia Bay, Newfoundland, peaked in most cases in June and was at a minimum in October or November. Water temperature, partial fullness index (IP) and gonado‐somatic index (IG) explained between 31 and 52% of the monthly variability in growth. Temperature and IP of capelin Mallotus villosus had significant effects on growth of all age groups and explained most of the variance for ages 6–8 and 4–5 years, respectively. The IP of large invertebrates (ages 4 to 7 years), sandlance (Ammodytes sp. age 6 years) and demersal fishes (age 9 years) had age‐specific effects in the model. Overall, amphipods, decapods and echinoderms dominated the Atlantic cod diet in most seasons, but fish consumption by Atlantic cod was high in June and July, particularly on capelin. The rapid increase in somatic mass during June and July occurred despite cold water temperatures ( < 3° C at 50 m) and moderate to high gonado‐somatic index. The findings of this study suggest that when food was not a limiting factor, growth tended to increase even when Atlantic cod occupied colder waters, but when food was limiting, the opposite may have occured.

Alternative Methods for Measuring Energy Content in Winter Flounder

AbstractIndices of energy reserves may represent interesting parameters that can be used as bioindicators in environmental studies. The goal of this study was to identify a water–energy model that could predict energy reserves in winter flounder Pseudopleuronectes americanus. Winter flounder kept in captivity and fed different food types (either capelin Mallotus villosus or Atlantic herring Clupea harengus, amphipods Anonyx sarsi, and wet pellets) for 2, 5, and 14 months and wild fish captured in May, July, and October were used to show a large range in energy content. High levels of correlation were observed between water and energy contents in fish carcasses (r2 = 0.82) and muscle (r2 = 0.75). However, the biochemical composition of the liver remained relatively constant, despite changes in the hepatosomatic index. The condition factor (somatic weight/length3) was associated with energy reserves (i.e., water contents), but the coefficients of determination were smaller (0.18 < r2 < 0.34). We found that muscle water content, which can easily be determined, is an efficient way to accurately predict energy reserves in winter flounder.

Effect of wintering area and climate on the survival of adult Atlantic puffins Fratercula arctica in the eastern Atlantic

Despite contrasting population trends ranging from -3 to +11% per annum, the annual survival rates of Atlantic puffins Fratercula arctica in the 5 colonies spanning the species range in the east Atlantic were virtually identical over a 10 to 15 yr period, giving no support to the hypothesis that variation in population growth rates is driven by adult survival. The extent to which survival varied among years differed markedly between colonies. Similarities between colonies in the patterns of inter-annual variation in survival did not reflect similarities in wintering areas, as indicated by recov- eries of ringed birds, nor the geographic proximity of the colonies. However, survival in 4 of the 5 colonies correlated with sea surface temperatures around each colony 2 yr earlier. The relationship between survival and sea temperature was positively correlated with the effects of sea temperature on recruitment of the Atlantic puffin's main prey species, the lesser sandeel Ammodytes marinus, the herring Clupea harengus and the capelin Mallotus villosus.

Oceanographic conditions structure forage fishes into lipid-rich and lipid-poor communities in lower Cook Inlet, Alaska, USA

Forage fishes were sampled with a mid-water trawl in lower Cook Inlet, Alaska, USA, from late July to early August 1996 to 1999. We sampled 3 oceanographically distinct areas of lower Cook Inlet: waters adjacent to Chisik Island, in Kachemak Bay, and near the Barren Islands. In 163 tows using a mid-water trawl, 229 437 fishes with fork length <200 mm were captured. More than 39 species were captured in lower Cook Inlet, but Pacific sand lance Ammodytes hexapterus, juvenile Pacific herring Clupea pallasi, and juvenile walleye pollock Theragra chalcogramma comprised 97.5% of the total individuals. Both species richness and species diversity were highest in warm, low- salinity, weakly stratified waters near Chisik Island. Kachemak Bay, which had thermohaline values between those found near Chisik Island and the Barren Islands, had an intermediate value of species richness. Species richness was lowest at the Barren Islands, an exposed region that regularly receives oceanic, upwelled water from the Gulf of Alaska. Non-metric multidimensional scaling (NMDS) was used to compute axes of species composition based on an ordination of pairwise site dissimilarities. Each axis was strongly rank-correlated with unique groups of species and examined separately as a function of environmental parameters (temperature, salinity, depth), area, and year. Oceanographic parameters accounted for 41 and 12% of the variability among forage fishes indicated by Axis 1 and Axis 2, respectively. Axis 1 also captured the spatial variability in the upwelled area of lower Cook Inlet and essentially contrasted the distribution of species among shallow, nearshore (sand lance, her- ring) and deep, offshore (walleye pollock) habitats. Axis 2 captured the spatial variability in forage fish communities from the north (Chisik Island) to the south (Barren Islands) of lower Cook Inlet and essen- tially contrasted a highly diverse community dominated by salmonids and osmerids (warmer, less saline) with a fish community dominated by Pacific sand lance (colder, more saline). Axis 3 reflected the negative spatial association of capelin Mallotus villosus and Pacific cod Gadus macrocephalus. Correlations of year with Axes 1 and 3 indicate that from 1996 to 1999 the forage fish community sig- nificantly decreased in lipid-poor gadids (walleye pollock and Pacific cod), and significantly increased in lipid-rich species such as Pacific sand lance, Pacific herring, and capelin.

Diel variation in feeding rate and prey composition of herring and mackerel in the southern Gulf of St Lawrence

Diel feeding patterns of herring Clupea harengus and mackerel Scomber scombrus in the southern Gulf of St Lawrence were examined based on samples obtained by midwater trawling between 19 and 26 June 2001. Within 3 h time periods, stomach contents tended to be more similar between fish from the same tow than between fish from different tows. Thus, in contrast to previous diet studies, which have used individual fish stomachs as independent observations, tow was used as the experimental unit in statistical analyses in this study. Diel patterns in stomach fullness were identified using generalized additive models. Two peaks in stomach fullness occurred for herring, one in the morning and the other in the evening. Mackerel showed an increase in feeding intensity throughout the day with a peak in mid‐afternoon. The diel changes in stomach contents suggested rapid gastric evacuation rates for both species, especially for herring. The estimate of the instantaneous evacuation rate for herring was twice that for mackerel. Calanus copepods (mainly C. hyperboreus), fishes (mainly capelin Mallotus villosus) and euphausiids were the main prey found in the stomachs of both species. Calanus copepods dominated the diet of herring regardless of time period. They also dominated the diet of mackerel during the late afternoon, evening and night while fishes and euphausiids were dominant during the morning and early afternoon. These diel patterns emphasize the need for sampling throughout the day and night in order to estimate ration and diet composition for bioenergetic and ecosystem models.

Stomach Contents of Breeding Common Murres Caught in Gillnets off Newfoundland

Abstract We examined the stomach contents of 64 male and 43 female Common Murres (Uria aalge) caught in gillnets during late chick rearing/early chick departure period in August 2002 near breeding colonies in Witless Bay, Newfoundland, Canada. Twenty-six percent of stomachs contained no food. All others contained exclusively fish, and Capelin (Mallotus villosus) was the only fish positively identified. Gravid female Capelin were found in 82% of murre stomachs with contents. The number of fish ingested by murres differed between the sexes, with a mean of 2.7 fish in male stomachs and 1.6 fish in female stomachs. Mean mass of stomach contents did not differ between the sexes (males: 27.0 g; females: 22.6 g). Overall, results were similar to Common Murre diets recorded in the 1980s, despite changes in Capelin distribution and biology. The sample of Common Murres collected as gillnet bycatch was male-biased (59%). Males may have been more vulnerable to being caught in gillnets, perhaps because they were engag...

Gametogenesis in capelin, Mallotus villosus (Müller), in the northwest Atlantic Ocean

Capelin (Mallotus villosus) can be regarded as the most important prey item in the northwest Atlantic Ocean. The health and availability of this species are of fundamental importance for the successful growth and reproduction of many other fishes, whales, and birds. In spite of the clear need to understand this species, the life history of the capelin, especially its reproductive biology, is not well understood. This study substantially improves our knowledge of the reproductive biology of capelin and should be of particular interest to resource managers and administrators. Capelin gonads were analysed over three successive seasons using fish collected during beach spawning (June and July 1993, July 1994, July 1995) or trawled between spawnings, with 11 separate samples (fall, winter, and spring from October 1993 to June 1995). Few immature fish were collected in the trawls; 13/130 (10%) males and 3/150 (2%) females. No recovering (postspawning) males were found in the trawls, but 8/150 (5.3%) recovering females were identified on the basis of large residual oocytes (ovulated or unovulated) and (or) (in the fall) a thicker ovarian wall. Recovering females were identified as late as 10 months post spawning on the basis of residual oocytes. The essential semelparity of males was supported by a lack of apparent spermatogonia during advanced spermatogenesis, whereas the females' capacity to spawn in a subsequent year (iteroparity) was confirmed by the presence of small nonvitellogenic oocytes when other cells were in late oogenesis, in addition to the identification of recovering fish. Oocytes were separable into four stages (potential year classes) and changes occurred in all oocyte stages throughout the cycle of oogenesis. Gametogenesis was more advanced in longer fish, indicating that larger fish spawn earlier than smaller fish.

Consequences of foraging trip duration on provisioning behaviour and fledging condition of common murres Uria aalgae

We examine the provisioning constraints of a pursuit‐diving seabird in a cold ocean regime by comparing the behaviour of common murres Uria aalge rearing chicks at two colonies in the Northwest Atlantic during 1998‐2000. Funk Island is the largest (340,000–400,000 breeding pairs) and most offshore (60 km) colony of common murres in eastern Canada. Seventy‐five percent of the Northwest Atlantic population of common murres breeds on this island. Great Island is one island within the Witless Bay Ecological Reserve, which is the second largest breeding aggregation (100 000 breeding pairs) and is located near‐shore (2 km). The primary forage fish species in Newfoundland waters is capelin Mallotus villosus, which spawns on or near coastal beaches during summer. Therefore, the two study colonies differ in their distance to food resources and colony size. It is within this natural context that we compare: (1) prey types and frequency of delivery (amount of prey), (2) parental time budgets, and (3) the mass and condition (mass/wing length) of fledglings at both colonies. Similarly sized female capelin (100–150 mm) were delivered to chicks at both colonies. Foraging time per day per parent, a proxy of foraging effort, was similar at both colonies (Great Island: 5.1 h; Funk Island: 5.5 h), as was the percentage of time spent with mates (Great Island: 12.3%; Funk Island: 10.9%). Foraging trips, however, were longer at Funk Island (4.1 h) than at Great Island (2.9 h). This resulted in lower feeding rates of chicks (0.17 feeds per h) and poorer condition of fledglings (2.9 g/mm) at Funk Island compared to those at Great Island (0.22 feeds per h; 3.9 g/mm). We hypothesize that provisioning efforts are constrained at Funk Island by (1) distant food resources and increased competitor density, resulting in longer foraging trip durations and (2) the time spent paired with mates at the colony, which may reflect a minimum time required to maintain breeding sites due to higher breeding densities at Funk Island compared to Great Island. Demographic consequences of this poor fledgling condition at Funk Island are unknown, but fledglings may sufficiently accelerate growth at sea due to their closer proximity to an important nursery area. If fledgling survival is compromised, however, the lower potential for growth at Funk Island will impact the entire Northwest Atlantic population of common murres.

Signals from seabirds indicate changing biology of capelin stocks

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 258:253-261 (2003) - doi:10.3354/meps258253 Signals from seabirds indicate changing biology of capelin stocks Gail K. Davoren*, William A. Montevecchi Biopsychology Programme, Departments of Biology and Psychology, Memorial University, St. John's, Newfoundland A1B 3X9, Canada *Email: z73gkd@ mun.ca ABSTRACT: Key forage species lie at the core of complex marine food webs, providing essential linkages among trophic levels. We examined the interactions of an important forage and commercial fish, capelin Mallotus villosus, and its primary avian predator, the common murre Uria aalge, in the NW Atlantic. Murres are capelin specialists and robust samplers of capelin biology. During the 1990s, the coldest surface-water event in the past 50 to 100 yr occurred in the NW Atlantic (1991), and the eastern Canadian ground-fishery was closed (1992). Concordantly, the biology and behaviour of capelin has undergone very substantial changes. We examined parental food deliveries and production at the world¹s largest common murre colony on Funk Island off the northeast coast of Newfoundland throughout the 1990s. Murres delayed breeding and delivered smaller and lower quality capelin to their chicks. These changes, corroborated with independent fisheries data, resulted in poor condition of murre chicks, indicating significant effects of changing capelin demographics at higher trophic levels. The diets of the murre chicks indicate that the composition of the capelin population has shifted from high size diversity to mainly smaller capelin. We hypothesize that this change resulted from the elimination of the larger-sized and earlier-spawning genotype and that the NW Atlantic capelin population is exhibiting signs of reduced reproductive potential that likely reflects lower spawning biomass. KEY WORDS: Predator-prey interaction · Bio-indicator · Ecosystem dynamics · Common murre · Uria aalge · Capelin · Mallotus villosus Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 258. Online publication date: August 29, 2003 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2003 Inter-Research.

Distributional patterns of a marine bird and its prey: habitat selection based on prey and conspecific behaviour

We examined distributional patterns of a pursuit-diving seabird, the common murre Uria aalge, and its fish prey, capelin Mallotus villosus, within the avian foraging range of the largest murre colony in eastern North America: Funk Island, Newfoundland. During chick-rearing, the foraging habitat was previously partitioned into: (1) a high-quality area, 45 km from the colony where energy- rich capelin schools were found, which were spatially and temporally persistent and (2) a low-quality area, 60 km from the colony where schools were composed of lower-energy capelin that were ephemeral. At the scale of the foraging range (meso-scale: 1 to 100 km), murres were highly clustered into 25% of the surveyed area, with fewer murres in the low-quality relative to the high-quality area. There were tighter associations among murre and capelin aggregations in the low-quality (1.2 ± 0.2 km) relative to the high-quality area (2.6 ± 0.4 km). This likely resulted from the divergent capelin behaviour and, thus, different foraging strategies used by murres to search for (e.g. memory vs local enhancement) and capture prey. At fine spatial scales (250 m 2 ) within foraging areas, murres were found at lower densities (mode: 2 murres), revealing that interference competition among individuals may be important during prey capture. Modeling revealed that at >50 murres per 250 m 2 in the high- quality area, a murre would have a >90% chance of increasing its foraging efficiency by switching to forage in the low-quality area. Overall, this scale-dependent aggregative behaviour of murres sug- gests that cooperative foraging among conspecifics may be important in locating prey at the scale of a foraging range, or murres may simply aggregate in areas of high prey abundance, but competitive interactions among conspecifics become important at the scale of prey capture.

The code of the long-term biomass cycles in the Barents Sea

Abstract Barents Sea capelin (Mallotus villosus), Norwegian spring-spawning herring (Cluea harengus), and Northeast Arctic cod (Gadus morhua) have been associated with large fluctuations of biomass growth. The cause of these large fluctuations has been poorly understood and led to problems in biomass management. The identification of a deterministic cause would provide the possibility of forecasting future biomass fluctuations. In this investigation, the Kola Section sea temperature and the biomasses of capelin, herring, and cod have been analyzed by a wavelet transform to identify the source of the long-term cycles. The wavelet analysis shows that the Kola Section temperature has dominant cycles at the lunar-nodal tide cycles of 3×18.6=55.8, 18.5 and 18.6/3 = 6.2 years. The recruitment of Barents Sea capelin, Norwegian spring-spawning herring, and Northeast Arctic cod has adopted an optimal recruitment cycle close to the stationary 6.2 years Kola temperature cycle. Long-term biomass growth is correlated to the phase relation between the biomass eigen-frequency cycle and the Kola temperature cycles. The biomasses of capelin, herring and cod have long-term growth when the 6.2 and 18.6 years Kola temperature cycles are positive at the same time. There is a long-term biomass reduction when the temperature cycles are not positive at the same time, and a biomass collapse when the temperature cycles are negative at the same time. The deterministic property of the 18.6 years lunar-nodal tide provides a new way of long-term biomass forecasting over periods of 50–80 years or more.

Isolation and characterization of DNA microsatellites for capelin Mallotus villosus population genetic studies

This study reports on the isolation and characterization of capelin Mallotus villosus DNA microsatellites and their potential use in population genetic studies. High numbers of dinucleotide repeats were detected among the isolated microsatellites. Primers and polymerase chain reaction conditions were developed for 17 polymorphic microsatellite markers, and in a test panel of 60 capelin the number of alleles at each locus ranged from 4 to 63, and observed heterozygosity ranged from 0.11 to 0.95. Six loci showed an excess of homozygotes, presumably due to the presence of null alleles. The 11 other loci showed statistically significant population differentiation between samples from the NE and NW Atlantic, while little differentiation was detected within each of these regions.

Juvenile capelin (Mallotus villosus) off Newfoundland and Labrador in the 1990s

Anderson, J. T., Dalley, E. L., and O'Driscoll, R. L. 2002. Juvenile capelin (Mallotus villosus )o ff Newfoundland and Labrador in the 1990s. - ICES Journal of Marine Science, 59: 917-928. Juvenile capelin, Mallotus villosus (Muller), 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 (r 2 =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 (5-8C) 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 )a nd sandlance (Ammodytes sp.) were abundant to the north and south respectively. 2002 International Council for the Exploration of the Sea. Published by Elsevier Science Ltd.

Relationship between the lipid composition of the Anadyr capelin Mallotus villosus and its physiological state

The lipid composition of muscle tissue in the capelin Mallotus villosus from Anadyr population was studied in connection with its physiological state, location, and season of fishery. The content of lipids in sexually mature Anadyr capelin in July–October rose from 8.5 to 11.8%, which is slower than the process of lipid accumulation in the capelin of the related Pribylov population. A predominance was confirmed of the total fatty acids 20 : 1 over the total acids 22 : 1 (the difference was about 15% ) in the lipids of the mature fattening capelin, as well as predominance of the total content of these two monoenoic acids in males compared with females. In the Anadyr capelin, this difference can be characterized as follows: Σ (20 : 1 + 22 : 1)males / Σ (20 : 1 + 22 : 1) females = 1.3. It is obvious that processes of accumulation of monoenoic fatty acids in reserve lipids proceed under strong metabolic control that differs in males and females.

Scale-dependent associations of predators and prey: constraints imposed by flightlessness of common murres

We examined the behavioural interactions of a mobile marine predator, the common murre Uria aalge, and its prey in a cold ocean regime in the context of shifting foraging constraints of the predator during various periods of the year. To do this, we explored the scale-dependent distribution patterns of murres in relation to their prey under 2 mobility regimes: (1) during the pre-breeding period when murres can fly and (2) during the post-breeding or moulting period when murres are flightless and are accompanied by flightless juveniles. In addition, we documented for the first time the relative contributions of different prey types in the diets of murres during moult using stable isotopic analysis. Flightless adult and juvenile murres were concentrated on a meso-scale (>100 km) in an area (nursery area) where significantly greater amounts of non-capelin, mainly crustaceans, were located in closely spaced aggregations. Accordingly, flightless murres had variable proportions of fish (capelin Mallotus villosus) and crustaceans in their diet, whereas breeding murres exclusively ate capelin. At fine- and coarse-scales (0.1 to 100 km), murres that could fly during pre-breeding tracked prey at smaller spatial scales (3 to 4 km) than flightless murres (6 to 9 km). We hypothesize that varying mobility regimes and energetic demands (activity levels) of murres during these 2 periods resulted in divergent perceptions of the foraging environment and subsequently in varying tracking scales of prey. This has important implications for the scale of study during different periods of the annual cycle of a predator, when varying constraints and trophic levels may interact to produce diverse behavioural responses to prey distribution and densities.

Atlantic puffin Fratercula arctica and common guillemot Uria aalge chick diet and growth as indicators of fish stocks in the Barents Sea

Between 1980 and 2000, Atlantic puffins Fratercula arctica and common guillemots Uria aalge breeding in the southern Barents Sea fed their chicks on varying proportions of 4 main cate- gories of prey: capelin Mallotus villosus, sandeels Ammodytes sp., I-group herring Clupea harengus and 0-group cod Gadus morhua. The varying proportions in both numbers and masses of the capelin, herring and cod in the seabird diet showed clear responses to the independently measured prey stocks. Amounts of capelin, herring and 0-group cod fed to Atlantic puffin chicks were good indica- tors of fish availability, whereas only amounts of herring fed to common guillemot chicks were corre- lated with the biomass of I-group herring in the region. The more general response by the Atlantic puffins probably results from their ability to catch only small fishes. Despite large interannual differ- ences in prey consumption plus gradual changes in meal sizes, the growth rates of the chicks of both species remained near their maximum, suggesting physiological restraints in growth during plentiful years and/or compensatory foraging behaviour by the adults.

Estimating the relative roles of dispersion and predation in generating regional differences in mortality rates of larval radiated shanny (Ulvaria subbifurcata)

We followed three patches of larval radiated shanny (Ulvaria subbifurcata) using drogued drifters to assess regional differences in growth and mortality rates. We estimate dispersive losses directly using local surveys of surface currents corrected for the tidally induced divergence caused by the lack of synopticity of our surveys. We also monitored the abundance of juvenile capelin (Mallotus villosus), the major planktivore in the region, using hydroacoustic integration. The pattern of divergence–convergence showed considerable temporal and spatial variability, which resulted in substantial changes in the inferred biological mortality rates. The net mortality rates appeared to be directly proportional to the local abundance of pelagic fish. As with other patch studies, we are limited in the number of observations we obtained, but the results of this multidisciplinary study do suggest a strong potential for prey–predator interactions between larvae and adult planktivorous fish.

Scale-dependent predator-prey interactions: the aggregative response of seabirds to prey under variable prey abundance and patchiness

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 231:279-291 (2002) - doi:10.3354/meps231279 Scale-dependent predator-prey interactions: the aggregative response of seabirds to prey under variable prey abundance and patchiness Per Fauchald*, Kjell Einar Erikstad Department of Biology, Faculty of Science, University of Tromsø,9037 Tromsø, Norway and Norwegian Institute for Nature Research, Division of Arctic Ecology, The Polar Environmental Center, 9296 Tromsø, Norway *E-mail: per.fauchald@nina.no ABSTRACT: The aggregative response of seabirds to their prey has frequently been measured through their spatial coherence during ship board surveys. In this study, we investigate the aggregative response of murres Uria spp. to capelin Mallotus villosus in relation to yearly changes in capelin abundance and patchiness from a 9 yr data set collected in the Barents Sea. A recent analysis on the spatial distribution of capelin and murres in the Barents Sea reported a hierarchical patch structure, whereby small-scale patches were nested within patches at larger scales. In the present study we carry out similar analyses for each of the 9 years. During the 9 yr period, the estimated total biomass of capelin varied between 100000 and 7300000 t. We identified 2 hierarchical levels of patchiness with characteristic scales of 200 to 300 km and 70 km respectively. We found close relationships between yearly variation in capelin abundance, capelin patchiness and the concordance between capelin and murres at both levels. The patchiness of capelin, as measured by the first-order spatial autocorrelation, increased with increasing capelin abundance at the large-scale level, and there was a similar tendency at the small-scale level. At the large-scale level, the spatial concordance between murres and capelin increased with both increasing capelin density and increasing capelin patchiness. At the small-scale level, the concordance between murres and capelin increased with increasing capelin patchiness. Our results suggest that increased prey patchiness and increased prey abundance enhance the possibility of murres finding satisfactory capelin concentrations. The reduction in prey patchiness with low prey abundance might force predators to switch to other prey items, and might therefore have a stabilizing effect on predator-prey interactions. KEY WORDS: Spatial distribution · Hierarchical patch structure · Capelin · Mallotus villosus · Murre · Uria spp.· Barents Sea Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 231. Online publication date: April 23, 2002 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2002 Inter-Research.