Diet of harp seals (Phoca groenlandica) in nearshore waters of the northwest Atlantic during 1990 – 1993

1995 ◽  
Vol 73 (10) ◽  
pp. 1805-1818 ◽  
Author(s):  
John W. Lawson ◽  
Garry B. Stenson ◽  
Dave G. McKinnon
Keyword(s):  
Gadus Morhua ◽  
Atlantic Cod ◽  
Stomach Contents ◽  
Clupea Harengus ◽  
Relative Importance ◽  
Northwest Atlantic ◽  
Arctic Cod ◽  
Diet Diversity ◽  
Phoca Groenlandica ◽  
Capelin Mallotus Villosus

The nearshore diet of northwest Atlantic harp seals (Phoca groenlandica) was determined by reconstructing the contents of 1167 prey-containing stomachs (78.3% of 1490) collected from 1990 to 1993. Although harp seals consumed at least 62 species, 6 accounted for most of the mass consumed and their relative importance varied by area. Based on percent wet mass, sculpins (Cottidae) and Arctic cod (Boreogadus saida) were the main components of the diet of older seals (> 1 year old) off Labrador, whereas Arctic cod and Atlantic herring (Clupea harengus) were the main prey of seals from northeastern Newfoundland. A more diverse diet was observed in seals taken off the west coast of Newfoundland, where capelin (Mallotus villosus), herring, Atlantic cod (Gadus morhua), redfish (Sebastes spp.), and Arctic cod were the main species. Redfish and Atlantic cod were important to seals along the south coast of Newfoundland. Eighty percent of fish consumed were less than 18 cm long, smaller than those taken by commercial fisheries. Pups (less than 1 year old) consumed fewer and smaller prey of a less varied assortment. Annual and seasonal variation in the diets was observed in the collection from northeastern Newfoundland. Arctic cod was the major prey consumed throughout the year by seals of all ages, although the relative importance of herring, capelin, and squid (Teuthoidea) increased during the summer. Invertebrates and capelin made up a greater proportion of the diet in 1992, owing to a decline in consumption of Arctic cod. This finding was associated with a decrease in the mass of stomach contents. Diet diversity did not change significantly over the study period.

Diet of northwest Atlantic harp seals (Phoca groenlandica) in offshore areas

1997 ◽  
Vol 75 (12) ◽  
pp. 2095-2106 ◽  
Author(s):  
John W. Lawson ◽  
Garry B. Stenson
Keyword(s):  
Gadus Morhua ◽  
Prey Species ◽  
Atlantic Cod ◽  
Greenland Halibut ◽  
Sand Lance ◽  
Northwest Atlantic ◽  
Grand Banks ◽  
Phoca Groenlandica ◽  
Capelin Mallotus Villosus ◽  
Greenland Halibut Reinhardtius Hippoglossoides

The offshore diet of harp seals (Phoca groenlandica) in the northwest Atlantic was determined by reconstructing the contents of prey-containing stomachs (399 of 724) recovered during 1980–1995. The importance of prey species varied seasonally and geographically. Pups (< 6 months old) usually consumed invertebrates, capelin (Mallotus villosus), and sand lance (Ammodytes dubius). Subadults (6 months to 4 years old) consumed capelin and Arctic cod (Boreogadus saida) in the northern part of their range but sand lance and capelin on the Grand Banks. Adults consumed invertebrates such as shrimp (Pandalus sp.) and Natantia (amphipods) when they were collected on the northern Labrador Shelf, but ate capelin, Greenland halibut (Reinhardtius hippoglossoides), and Atlantic cod (Gadus morhua) on the southern Labrador Shelf. On the Grand Banks they consumed pleuronectids, sand lance, and capelin. Atlantic cod were rarely eaten by seals not caught by commercial trawlers. In contrast to the seals' nearshore diet, capelin were the principal prey on the Grand Banks and Labrador Shelf. Sand lance and Greenland halibut were also important. The contrast between near- and off-shore diets illustrates the importance of geographical variation in the contribution of a single prey species to the diet, especially in attempts to extrapolate consumption of specific prey.

Seasonal Variation in the Diet of Harp Seals (Phoca groenlandica) from the Gulf of St. Lawrence and Western Hudson Strait

1993 ◽  
Vol 50 (7) ◽  
pp. 1363-1371 ◽  
Author(s):  
Gregor Gilpin Beck ◽  
Michael O. Hammill ◽  
Thomas G. Smith
Keyword(s):  
Gadus Morhua ◽  
Atlantic Cod ◽  
Stomach Contents ◽  
Fish Prey ◽  
Lawrence Estuary ◽  
Phoca Groenlandica ◽  
Capelin Mallotus Villosus ◽  
Gross Energy ◽  
St Lawrence Estuary ◽  
Magdalen Islands

Of 247 harp seal (Phoca groenlandica) stomachs collected between December 1988 and October 1990 from western Hudson Strait (autumn), the northern Gulf of St. Lawrence (December), the St. Lawrence estuary (winter and April), and the Magdalen Islands (March), 140 (57%) contained food. The Magdalen Islands sample contained significantly more empty stomachs (62%, n = 164) than those from all other locations. Both the unreconstructed mass of stomach contents and the proportion of fish and invertebrate prey within individual stomachs varied significantly with location and season. Harp seals obtained from the northern Gulf of St. Lawrence during their southward migration fed less intensively, and on a wider variety of both invertebrate and fish prey, notably Parathemisto libellula, Pandalus sp., sand lance (Ammodytes sp.), and Atlantic cod (Gadus morhua). Feeding was more intensive and specialized in Hudson Strait and the St. Lawrence estuary where capelin (Mallotus villosus) dominated in the diet. Capelin contributed 89 and 98% of gross energy in samples from Hudson Strait (1990) and the estuary (April). The number of capelin per stomach consumed by seals from the St. Lawrence estuary in April was high (169.4 ± 58.9, mean ± SD, n = 9). The mean estimated lengths of capelin and cod consumed were 132 and 140 mm.

Pelagic fishes and the cod recruitment dilemma in the Northwest Atlantic

2000 ◽  
Vol 57 (7) ◽  
pp. 1321-1325 ◽  
Author(s):  
D P Swain ◽  
A F Sinclair
Keyword(s):  
Gadus Morhua ◽  
Atlantic Cod ◽  
Negative Relationship ◽  
Early Life History ◽  
Recruitment Rate ◽  
Clupea Harengus ◽  
Northwest Atlantic ◽  
Life History Stages ◽  
Pelagic Fishes ◽  
Predatory Fishes

Like most other stocks of Atlantic cod (Gadus morhua) in the Northwest Atlantic, cod in the southern Gulf of St. Lawrence declined to low abundance in the early 1990s. Recovery has been slow in contrast with the rapid recovery from similar levels of abundance in the mid-1970s. This difference reflects remarkably high prerecruit survival of cod in the earlier period of low abundance rather than unusually poor survival in the 1990s. The period of high prerecruit survival of cod coincided with the collapse of herring (Clupea harengus) and mackerel (Scomber scombrus) stocks resulting from overfishing. These pelagic fishes are potential predators or competitors of the early life history stages of cod. We report a strong negative relationship between the biomass of these pelagic fishes and recruitment rate of southern Gulf cod. This is consistent with the recent suggestion that the success of large predatory fishes may depend on "cultivation" effects in which the adults crop down forage fishes that are predators or competitors of their young. Our results also point to the possibility of a triangular food web involving cod, seals, and pelagic fishes, making it difficult to predict the effect of a proposed cull of seals on the recovery of cod.

Production Responses for Multi-species Fisheries

1981 ◽  
Vol 38 (11) ◽  
pp. 1393-1404 ◽  
Author(s):  
R. J. Agnello ◽  
L. G. Anderson
Keyword(s):  
New England ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Clupea Harengus ◽  
Categorical Variables ◽  
Melanogrammus Aeglefinus ◽  
Target Species ◽  
Northwest Atlantic ◽  
Fisheries Economics ◽  
Log Linear

Production equations are estimated for five major species of fish harvested in the Northwest Atlantic including Atlantic cod (Gadus morhua), haddock (Melanogrammus aeglefinus), flounder (Pleuronectiformes), redfish (Sebastes marinus), and herring (Clupea harengus) using data collected by the International Commission for the Northeast Atlantic Fisheries from 1960 to 1974. A log-linear regression specification is used in which the relationship between catch of a vessel and several factors including days fished and vessel characteristics is estimated simultaneously. Vessel characteristics are represented as (0, 1) categorical variables, and include a variable indicating the target species designated by the caption. Various settings for the target species variables allow the estimated equation to represent either a by-catch or target catch equation. The production parameters estimated by the regressions are used to analyze the effects of current quotas set by the New England Fisheries Management Council. For some fleets we find a likelihood of idle capacity given the current quotas.Key words: fisheries economics, multi-species harvesting, Northwest Atlantic fisheries

scholarly journals A note on stomach contents of minke whales (Balaenoptera acutorostrata) in Icelandic waters

2000 ◽  
Vol 2 ◽  
pp. 82 ◽  
Author(s):  
Jóhann Sigurjónsson ◽  
Anton Galan ◽  
Gísli A Víkingsson
Keyword(s):  
Food Habits ◽  
Gadus Morhua ◽  
Prey Species ◽  
Stomach Contents ◽  
Clupea Harengus ◽  
Balaenoptera Acutorostrata ◽  
Minke Whales ◽  
Capelin Mallotus Villosus ◽  
Available Information ◽  
Icelandic Waters

There is limited available information on food habits of minke whales (Balaenoptera acutorostrata) in coastal Iceland. Sixty-eight minke whales were examined for stomach contents; 51.5% contained fish only, 22.1 % krill (Euphausiacea) only, 25.0% fish and krill together, and one animal (l.5%) had no food remains in the stomach. The fish species identified were capelin (Mallotus villosus), sandeel (Ammodytidae), cod (Gadus morhua) and herring (Clupea harengus). Two species of krill were identified; Thysanoessa raschii and Meganyctiphanes norvegica. Sandeel was the dominant prey species in the western and southwestern areas, while capelin and krill were more frequently found in animals sampled in North Iceland.

Stomach contents of harbour porpoises, Phocoena phocoena (L.), from the Bay of Fundy

1989 ◽  
Vol 67 (9) ◽  
pp. 2140-2146 ◽  
Author(s):  
Cheri A. Recchia ◽  
Andrew J. Read
Keyword(s):  
Gadus Morhua ◽  
Prey Species ◽  
Atlantic Cod ◽  
Caloric Intake ◽  
Stomach Contents ◽  
Clupea Harengus ◽  
Spatial And Temporal Variation ◽  
Bay Of Fundy ◽  
Phocoena Phocoena ◽  
Total Caloric Intake

We examined contents from stomachs of 127 harbour porpoises (Phocoena phocoena) caught in groundfish gill nets in the western Bay of Fundy during June to September, 1985–1987. Relative importance of prey species was assessed using both numerical and caloric measures. Atlantic herring (Clupea harengus) was the most important prey species, contributing 80% of the total caloric intake, with some spatial and temporal variation. Silver hake (Merluccius bilinearis) and Atlantic cod (Gadus morhua) were also important, but together comprised only 17% of the total caloric intake. No differences were found in relative prey importance between adult porpoises of different reproductive conditions, but lactating females ingested more fish and had a significantly higher total caloric intake than nonlactating females or mature males. The diet of porpoises collected from the same area in 1969–1972 consisted of a higher proportion of pelagic prey species and a lower proportion of demersal species. This may be attributed to differences in capture method, as the earlier sample of porpoises was collected at the surface, while the present animals were captured at depths of 45–100 m.

Predator Stomachs as Sampling Tools for Prey Distribution: Atlantic Cod (Gadus morhua) and Capelin (Mallotus villosus)

1993 ◽  
Vol 50 (7) ◽  
pp. 1541-1547 ◽  
Author(s):  
Lenore Fahrig ◽  
George R. Lilly ◽  
Daniel S. Miller
Keyword(s):  
Gadus Morhua ◽  
Atlantic Cod ◽  
Stomach Contents ◽  
Mallotus Villosus ◽  
Predator Prey ◽  
Prey Distribution ◽  
Capelin Mallotus Villosus ◽  
Negative Effect ◽  
Predator Abundance ◽  
Bottom Depth

We demonstrate a direct relationship between the amount of prey (capelin, Mallotus villosus) in its predators' stomachs (Atlantic cod, Gadus morhua) and the biomass of the prey in the same localities. The relationship at a local scale implies that predator stomach contents can be used to estimate prey distribution. There is no evidence for either (1) a negative effect of local predator abundance on stomach contents (expected if local prey depletion and/or feeding interference occurs when predator density is high) or (2) a negative effect of the amount of other food in cod stomachs on the amount of capelin in the stomachs (expected if prey switching occurs). There is a negative effect of bottom depth on amount of capelin in cod stomachs as expected, since capelin are pelagic and cod are primarily bottom-dwelling, resulting in less vertical overlap between the species in deep water. This type of analysis may be useful in other predator–prey systems. Simultaneous stomach samples and independent biomass estimates of the prey are required, but once the model is built, it permits estimation of prey distribution in places and times when no direct survey of the prey can be done.

Variation in assimilation efficiency and digestive efficiency of captive harp seals (Phoca groenlandica) on different diets

1997 ◽  
Vol 75 (8) ◽  
pp. 1285-1291 ◽  
Author(s):  
John W. Lawson ◽  
Edward H. Miller ◽  
Elizabeth Noseworthy
Keyword(s):  
Atlantic Cod ◽  
Relative Concentration ◽  
Assimilation Efficiency ◽  
Clupea Harengus ◽  
Meal Size ◽  
Food Type ◽  
Digestive Efficiency ◽  
Greenland Halibut ◽  
Arctic Cod ◽  
Phoca Groenlandica

Digestive efficiency (DE) is influenced by many factors including food type or quality. Assimilation efficiency (AE) and DE of 12 captive harp seals (Phoca groenlandica) were estimated for five prey types in large outdoor seawater tanks. In trials of > 9 days' duration, the seals were fed Atlantic cod (Gadus morhua), Arctic cod (Boreogadus saida), Greenland halibut (Reinhardtius hippoglossoides), Atlantic herring (Clupea harengus), and capelin (Mallotus villosus). Fish were marked with inert tracers so that faecal samples could be matched to individual animals. AE (digestibility of dry matter) was estimated from the relative concentration of Mn2+ in food and faeces. DE (digestible energy) was estimated from the relative concentrations of both Mn2+ and energy in food and faeces. AE and DE values were high, but varied among the fish species (DE: Atlantic cod 93.5%; Arctic cod 93.5%; halibut 94.7%; capelin 95.7%; herring 96.6%). Both estimates of digestive efficiency were positively correlated with prey energy density. For most prey, AE and DE were not correlated with meal size, number of prey in a meal, size of prey, or seal body mass. However, digestive efficiency was greater in seals fed smaller Atlantic cod, or meals of greater mass. Quantifying estimates of digestive efficiency is important for formulating energy-based population consumption models, and so should be improved. It is recommended that more pinniped species be studied in captivity, that experiments last longer, and that the number of individuals studied be increased so that individual differences can be investigated.

Comparison of harbour seal diets in two inshore habitats of Atlantic Canada

1996 ◽  
Vol 74 (1) ◽  
pp. 125-135 ◽  
Author(s):  
W. D. Bowen ◽  
G. D. Harrison
Keyword(s):  
Gadus Morhua ◽  
Prey Species ◽  
Atlantic Cod ◽  
Atlantic Coast ◽  
Clupea Harengus ◽  
Harbour Seal ◽  
Bay Of Fundy ◽  
Alosa Pseudoharengus ◽  
Pseudopleuronectes Americanus ◽  
Capelin Mallotus Villosus

We studied the composition of harbour seal (Phoca vitulina) diets in two areas, the lower Bay of Fundy and along the northeastern coast of Nova Scotia, that differ in prey species diversity, bottom type, and physical oceanography. Prey remains were found in 250 of 470 harbour seal stomachs collected mainly from May to September between 1988 and 1992. Although 23 taxa were identified, four species, Atlantic herring (Clupea harengus), Atlantic cod (Gadus morhua), pollock (Pollachius virens), and short-finned squid (Illex illecebrosus), accounted for 84% of the estimated biomass of prey consumed in the two areas combined. Species, such as herring and squid, that dominated the diets in both habitats, also tended to be abundant in both habitats during the summer. Atlantic cod was the principal gadoid in the Bay of Fundy, whereas pollock was most important along the Atlantic coast. Differences in prey distribution and abundance appeared to account for differences in the contribution of the alewife (Alosa pseudoharengus), winter flounder (Pseudopleuronectes americanus), hake (Urophycis spp.), and capelin (Mallotus villosus) in the diet. Pronounced interannual variation in the species composition of diets was evident in both habitats. This variation was associated with broad-scale changes in prey abundance in some cases (e.g., squid and capelin) but not in others (e.g., Atlantic cod and pollock).

Parasites as biological tags of marine, freshwater and anadromous fishes in North America from the tropics to the Arctic

Parasitology ◽  
2014 ◽  
Vol 142 (1) ◽  
pp. 68-89 ◽  
Author(s):  
DAVID J. MARCOGLIESE ◽  
KYM C. JACOBSON
Keyword(s):  
North America ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Molecular Techniques ◽  
Clupea Harengus ◽  
The Arctic ◽  
Northwest Atlantic ◽  
Fish Stocks ◽  
The Pacific ◽  
Biological Tags

SUMMARYParasites have been considered as natural biological tags of marine fish populations in North America for almost 75 years. In the Northwest Atlantic, the most studied species include Atlantic cod (Gadus morhua), Atlantic herring (Clupea harengus) and the redfishes (Sebastes spp.). In the North Pacific, research has centred primarily on salmonids (Oncorhynchus spp.). However, parasites have been applied as tags for numerous other pelagic and demersal species on both the Atlantic and Pacific coasts. Relatively few studies have been undertaken in the Arctic, and these were designed to discriminate anadromous and resident salmonids (Salvelinus spp.). Although rarely applied in fresh waters, parasites have been used to delineate certain fish stocks within the Great Lakes-St Lawrence River basin. Anisakid nematodes and the copepod Sphyrion lumpi frequently prove useful indicators in the Northwest Atlantic, while myxozoan parasites prove very effective on the coast and open seas of the Pacific Ocean. Relative differences in the ability of parasites to discriminate between fish stocks on the Pacific and Atlantic coasts may be due to oceanographic and bathymetric differences between regions. Molecular techniques used to differentiate populations and species of parasites show promise in future applications in the field.

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