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.

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.

Assimilation efficiency of prey in the Hawaiian monk seal (Monachus schauinslandi)

1999 ◽  
Vol 77 (4) ◽  
pp. 653-660 ◽  
Author(s):  
Gwen D Goodman-Lowe ◽  
James R Carpenter ◽  
Shannon Atkinson
Keyword(s):  
Control Diet ◽  
Assimilation Efficiency ◽  
Nitrogen Retention ◽  
Metabolizable Energy ◽  
Clupea Harengus ◽  
Digestive Efficiency ◽  
Hawaiian Monk Seal ◽  
Monachus Schauinslandi ◽  
Gross Energy ◽  
Monk Seals

Assimilation efficiency, digestive efficiency, metabolizable energy, and nitrogen retention in three captive adult male Hawaiian monk seals (Monachus schauinslandi) were measured with the indigestible marker chromic oxide for four experimental diets: a control diet of herring (Clupea harengus) and three test diets consisting of flagtail (Kuhlia sandvicensis), squid (Loligo sp.), and lobster (Panulirus marginatus), each of which was used in combination with herring. The addition of all three test prey to herring decreased the digestibility of gross energy by a mean of 3.58 ± 3.89%. Assimilation efficiency of gross energy was 96.1 ± 4.0% for herring, 73.8 ± 6.8% for flagtail, and 94.1 ± 5.7% for squid, but could not be determined for lobster. Digestive efficiency and metabolizable energy of the diets examined were high (4602.2 ± 247.1 and 4062.5 ± 178.4 kcal/d, respectively; 1 kcal = 4.18 kJ) and were positively correlated with the amount of gross energy ingested. Nitrogen retention was highest for the squid-herring diet (33.2 ± 1.2 g·d-1) followed by the lobster-herring diet (11.5 ± 3.3 g·d-1), the flagtail-herring diet (6.0 ± 0.0 g·d-1), and the herring (control) diet (-5.7 ± 1.6 g·d-1). This study indicates that prey which are both higher in protein and lower in fat than herring provide greater metabolizable energy for productive functions in Hawaiian monk seals.

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.

Accuracy and precision in stock separation of north-east Arctic and Norwegian coastal cod by otoliths - comparing readings, image analyses and a genetic method

2005 ◽  
Vol 56 (5) ◽  
pp. 753 ◽  
Author(s):  
Erik Berg ◽  
Tuula H. Sarvas ◽  
Alf Harbitz ◽  
Svein Erik Fevolden ◽  
Arnt Børre Salberg
Keyword(s):  
Visual Inspection ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Complete Separation ◽  
Arctic Cod ◽  
Genetic Method ◽  
North East ◽  
Accuracy And Precision ◽  
Growth Zones ◽  
The Difference

The distinction between north-east Arctic cod and Norwegian coastal cod, two major groups of Atlantic cod (Gadus morhua L.), has for many years been based on different distance and shape similarities between the two first translucent growth zones in the otoliths, subjectively decided by visual inspection in a binocular. To analyse the certainty of this technique, four independent readers have classified 263 cod otoliths in total from five different geographical areas. For three of the readers, between 82% and 89% of the classification results coincided with independent results based on genetic analyses. Further, 38 cod otoliths, where the readers were certain of the classification (21 north-east Arctic cod and 17 coastal cod) were classified by several image analysis methods. A complete separation was obtained by using the ratio of the circumferences of the two zones, providing a typical ratio of approximately 2 for coastal and 1.5 for north-east Arctic cod. The otolith method for separating the two types of cod has been considered adequately accurate in assessing the two stocks of cod. However, the method is sensitive to subjective interpretation, and action needs to be taken to minimise the difference in interpretation among otolith readers.

Fish Catches and Long-Term Tidal Cycles in Northwest Atlantic Fisheries: A Nonlinear Regression Approach

1987 ◽  
Vol 44 (11) ◽  
pp. 1890-1897 ◽  
Author(s):  
Paul Cabilio ◽  
David L. DeWolfe ◽  
Graham R. Daborn
Keyword(s):  
New England ◽  
Nonlinear Regression ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Significant Negative Correlation ◽  
Clupea Harengus ◽  
Atlantic Menhaden ◽  
Melanogrammus Aeglefinus ◽  
Grand Banks

Selected long-term fisheries catch data from the New England – Fundy area and the Grand Banks were examined for concordance between changes in fish catches and the 18.6-yr nodal cycle of the tides using a nonlinear regression model. Significant positive correlations were found for Atlantic cod (Gadus morhua), haddock (Melanogrammus aeglefinus), alewife (Alosa pseudoharengus), Atlantic herring (Clupea harengus harengus), and scallop (Placopecten magellanicus), with lag times that are biologically appropriate for the time from hatching to recruitment into the fishery. A significant negative correlation with the nodal cycle was evident for Atlantic menhaden (Brevoortia tyrannus), for which this area constitutes the most northerly part of its range. Cod catches on the Grand Banks showed no correlation with the nodal cycle. It is suggested that the correlations between the nodal cycle and the changes in fish catches are caused by correlated changes either in sea surface temperature or in productivity resulting from changes in the degree of vertical mixing.

Mitigation of harbour porpoise (Phocoena phocoena) by-catch in the gillnet fishery in the lower Bay of Fundy

1999 ◽  
Vol 56 (1) ◽  
pp. 113-123 ◽  
Author(s):  
Edward A Trippel ◽  
Michael B Strong ◽  
John M Terhune ◽  
Jeremy D Conway
Keyword(s):  
Gadus Morhua ◽  
Atlantic Cod ◽  
Field Testing ◽  
Harbour Porpoise ◽  
Clupea Harengus ◽  
Bay Of Fundy ◽  
Phocoena Phocoena ◽  
By Catch ◽  
Catch Rates ◽  
Wind Sea

Demersal gill nets equipped with acoustic alarms reduced harbour porpoise (Phocoena phocoena) by-catch rates by 77% over those without alarms in the Swallowtail area of the lower Bay of Fundy during field testing in August 1996 (68% reduction) and 1997 (85% reduction) (both years combined, three harbour porpoises in 249 alarmed nets versus 14 harbour porpoises in 267 nonalarmed nets). The alarms spaced 100 m apart along the net floatline produced a 0.3-s pulse at 10-12 kHz every 4 s at a level of 133-145 dB re 1 µPa at 1 m. In conditions of no rain and low wind (Sea State 0-2) the alarms were presumed to be clearly audible to harbour porpoises at ranges of 0.1-0.6 km. Catch rates of Atlantic herring (Clupea harengus), Atlantic cod (Gadus morhua), and pollock (Pollachius virens) were not significantly different in alarmed and nonalarmed nets (except in one season when pollock were caught in lower numbers in alarmed nets). Harbour porpoise by-catch and herring movements may be linked. During years of low herring abundance, we also observed low harbour porpoise entanglement rates.

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.

scholarly journals Specific dynamic action, apparent assimilation efficiency, and digestive rate in an arboreal pitviper, Trimeresurus stejnegeri stejnegeri

2008 ◽  
Vol 86 (10) ◽  
pp. 1139-1151 ◽  
Author(s):  
Tein-Shun Tsai ◽  
How-Jing Lee ◽  
Ming-Chung Tu
Keyword(s):  
Assimilation Efficiency ◽  
Specific Dynamic Action ◽  
Meal Size ◽  
Digestive Physiology ◽  
Postprandial Metabolism ◽  
Preferred Temperature ◽  
Time To Peak ◽  
Dynamic Action ◽  
Effects Of Temperature ◽  
Arboreal Snakes

The major aims of this study were to assess the effects of temperature (15–35 °C) and meal size (less than 30% snake mass) on the metabolism and digestive physiology of Trimeresurus stejnegeri stejnegeri Schmidt, 1925 and to compare the results with those of terrestrial snakes. Specific dynamic action (SDA), peak Vo2, and scope of peak Vo2 increased with meal size. Temperature had little effect on SDA. With regression analysis, we found that baseline metabolic rates of T. s. stejnegeri were generally smaller than that for frequent feeders and larger than that for infrequent feeders. We generalized three types of SDA profiles among T. s. stejnegeri and terrestrial snakes (including frequent and infrequent feeders). Trimeresurus stejnegeri stejnegeri had a more shallow and extended profile of postprandial metabolism, which did not support our hypothesis that the pace of digestive metabolism of arboreal snakes is faster than that of terrestrial snakes. The apparent assimilation efficiency (range 0.698–0.884) was significantly lower at 15 °C. At the preferred temperature (26.5–28.8 °C) for a postprandial 50 g snake, the simulated ratios of four parameters (time to peak Vo2, first defecation time, gastric digestion time, and final defecation time) to SDA duration approximated 0.2, 0.5–0.7, 0.7, and 1.1, respectively.

Metabolizable energy requirements for maintenance and faecal and urinary losses of juvenile harp seals (Phoca groenlandica)

1984 ◽  
Vol 62 (5) ◽  
pp. 769-776 ◽  
Author(s):  
K. M. Keiver ◽  
K. Ronald ◽  
F. W. H. Beamish
Keyword(s):  
Energy Intake ◽  
Weight Change ◽  
Assimilation Efficiency ◽  
Metabolizable Energy ◽  
Energy Requirements ◽  
Energy Losses ◽  
Feeding Frequency ◽  
Phoca Groenlandica ◽  
High Lipid ◽  
Gross Energy

Assimilation efficiency of energy in juvenile harp seals was 92.5–95.0% of gross energy intake when fed Atlantic herring and 72.2% when fed shrimp. Faecal energy losses increased directly with intake. Metabolizable energy (ME) ranged from 85.5 to 88.7% of gross energy intake for a diet of herring. Urinary energy losses increased directly with apparent digestible nitrogen intake. Faecal and urinary losses were not affected significantly by feeding frequency. Urine excretion indicated that feeding causes a diuresis, associated with increased energy, nitrogen, and ash excretion. A significant interaction was found for rate of weight change between feeding frequency and energy intake. Seals lost more weight at energy intakes below their maintenance level when fed four meals rather than two meals per day. Differences in rate of weight change with feeding frequency were not observed at other levels of energy intake. Maintenance energy requirements were estimated at 2658 kcal ME daily for seals fed two meals per day and 3514 kcal ME daily when fed four meals per day. Seals required approximately 3 times as much shrimp as herring of high lipid content to meet their energy requirements.

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