Digestion of pelagic Ctenophora and Cnidaria by fish

2003 ◽  
Vol 60 (7) ◽  
pp. 825-829 ◽  
Author(s):  
Mary N Arai ◽  
David W Welch ◽  
Adrienne L Dunsmuir ◽  
Melinda C Jacobs ◽  
Adrian R Ladouceur
Keyword(s):  
Chum Salmon ◽  
Salt Content ◽  
Stomach Contents ◽  
High Water ◽  
Organic Content ◽  
Oncorhynchus Keta ◽  
Energy Sources ◽  
Feeding Rates ◽  
Aequorea Victoria ◽  
Pleurobrachia Bachei

The diet of chum salmon (Oncorhynchus keta) can range from a primarily arthropod to a primarily gelatinous composition. Because no data exist for the digestion rates of gelatinous prey in any fish, it has not been possible to convert data on stomach contents to feeding rates. We measured rates of digestion to address this issue. In freely feeding age-0 chum salmon, the ctenophore Pleurobrachia bachei was digested almost completely within 1 h, whereas 70% of shrimp sections of similar mass remained after 5 h at 13°C. To examine the fast progress of digestion at smaller intervals, age-0 and age-1 fish were also force-fed with whole P. bachei or sections of the hydromedusa Aequorea victoria. These data emphasize the necessity of examining fish stomachs very quickly after capture. Although gelatinous organisms have high water and salt content relative to their organic content, given the rapid rates of digestion observed, coelenterates might rival arthropods as energy sources.

Predation on pelagic coelenterates: a review

2005 ◽  
Vol 85 (3) ◽  
pp. 523-536 ◽  
Author(s):  
Mary Needler Arai
Keyword(s):  
Food Webs ◽  
Salt Content ◽  
Stomach Contents ◽  
High Water ◽  
Marine Ecosystems ◽  
Organic Content ◽  
Wide Range

Coelenterates (cnidaria and ctenophores) are well recognized as predators in food webs of marine ecosystems but are less often considered as prey. This is partly because they are digested very rapidly. In studies based on predator stomach contents the measured masses of different prey organisms are rarely scaled by their relative rates of digestion. Predators that are frozen and thawed, or for which whole stomachs are placed in preservatives, may have already lost much of their coelenterate content when they are examined. There is also a tendency to assume that gelatinous organisms, with their high water and salt content relative to organic content, are poor food. However, given the high rates of digestion (and presumably of assimilation) coelenterates may provide sources of energy comparable to better recognized prey such as arthropods. It is already becoming well documented that a number of cnidaria and ctenophores as well as fish utilize gelatinous organisms as prey. Data is accumulating more slowly on predation by a wide range of other carnivores such as molluscs, arthropods, reptiles and birds.

scholarly journals Comparison of the swimming ability and upstream-migration behavior between chum salmon and masu salmon

2014 ◽  
Vol 71 (2) ◽  
pp. 217-225 ◽  
Author(s):  
Koji Miyoshi ◽  
Kazufumi Hayashida ◽  
Taku Sakashita ◽  
Makoto Fujii ◽  
Hisaya Nii ◽  
...  
Keyword(s):  
Swimming Speed ◽  
Chum Salmon ◽  
Swimming Performance ◽  
High Water ◽  
Masu Salmon ◽  
Oncorhynchus Keta ◽  
Upstream Migration ◽  
Migration Behavior ◽  
Spawning Ground ◽  
Long Distance

The spawning ground of chum salmon (Oncorhynchus keta) is usually located farther downriver than that of masu salmon (Oncorhynchus masou) in Hokkaido, Japan. To compare the swimming abilities of these two species, the relationship between swimming speed and oxygen consumption was compared using a swim tunnel in the laboratory. Then, the upstream-migration behaviors of chum salmon and masu salmon were compared using electromyogram telemetry at fish passages in the Toyohira River, Hokkaido. In the laboratory study, the standard metabolic rate of masu salmon was lower and the critical swimming speed (Ucrit) was faster than those of chum salmon. In the field study, the holding time needed to recover the swimming performance exceeding Ucrit at the fish passages and the trial number needed to pass the fish passages were significantly lower for masu salmon than chum salmon. These results revealed that masu salmon are more adaptable to extended swimming in high water velocity conditions than chum salmon and that masu salmon are better equipped for a long distance upstream migration to their spawning ground than chum salmon.

Deepwater Migrations of Chum Salmon (Oncorhynchus keta) along the Pacific Coast of Northern Japan

1992 ◽  
Vol 49 (11) ◽  
pp. 2307-2312 ◽  
Author(s):  
Yasuhiro Ueno
Keyword(s):  
Surface Waters ◽  
Chum Salmon ◽  
Pacific Coast ◽  
Depth Distribution ◽  
Stomach Contents ◽  
Oncorhynchus Keta ◽  
Southern Limit ◽  
Chum Salmon Oncorhynchus Keta ◽  
The Pacific ◽  
Northern Japan

Mature chum salmon (Oncorhynchus keta) were caught in bottom trawls off lwate Prefecture, northern Japan, in autumn. To document the incidence and depth distribution of these catches, records were kept of salmon caught by five trawlers that fished along the Pacific coast of northern Honshu during September–December 1986. During this period, 4337 chum salmon were caught at bottom depths ranging from 150 to 460 m with most taken from 200 to 350 m. Gonads and stomach contents were examined for 100 of these salmon. All were mature and close to spawning. Thirty-nine of the 100 stomachs examined were empty and the remaining 61 contained only a small quantity of food, averaging 2.4 g. Chum salmon may move at these depths to avoid the high temperatures of surface waters (12–20 °C) found in this area and to follow temperatures close to their thermal preferendum (3–11 °C) which are found near bottom. This phenomenon appears to be an adaptation of chum salmon near the southern limit of their range.

Interactions of fish and pelagic coelenterates

1988 ◽  
Vol 66 (9) ◽  
pp. 1913-1927 ◽  
Author(s):  
Mary Needler Arai
Keyword(s):  
Chum Salmon ◽  
Larval Fish ◽  
Trophic Position ◽  
Stomach Contents ◽  
Caloric Content ◽  
Feeding Rates ◽  
Intermediate Hosts ◽  
Important Species ◽  
Atlantic Mackerel ◽  
Commercially Important

Coelenterates may be predators or prey of fish, act as intermediate hosts for parasites, or provide shelter. At least 42 species of fish, including such commercially important species as the spiny dogfish, chum salmon, Atlantic mackerel, and various gadoids, include pelagic coelenterates in their diets. Coelenterates may represent a substantial proportion of the fish stomach contents and preliminary data on caloric content of coelenterates is available. However, in the absence of measured digestion rates it is not possible to calculate feeding rates or assess the dietary importance of coelenterates to fish. Similarly, although many instances of coelenterates eating larval fish are known, only a few measurements of predation rates based on feeding rates and abundances of predator and prey have yet been made. Recent studies with newer sampling methods indicate that the biomass of coelenterates, particularly large scyphomedusae, has been underestimated. Hence, much quantitative work needs to be done on the interactions of coelenterates with both fish and other marine groups to evaluate their trophic position and importance in pelagic ecosystems.

Detritus and Juvenile Salmon Production in the Nanaimo Estuary: I. Production and Feeding Rates of Juvenile Chum Salmon (Oncorhynchus keta)

1979 ◽  
Vol 36 (5) ◽  
pp. 488-496 ◽  
Author(s):  
M. C. Healey
Keyword(s):  
Body Weight ◽  
Food Intake ◽  
Food Chain ◽  
Chum Salmon ◽  
Oncorhynchus Keta ◽  
Average Weight ◽  
Feeding Rates ◽  
Chain Dynamics ◽  
Chum Salmon Oncorhynchus Keta ◽  
Juvenile Chum Salmon

Theories of food chain dynamics have important implications for the management of marine resources. As yet, however, there are few empirical studies of the food chain dynamics of resource species against which these theories can be judged. This paper compares the food requirements of juvenile chum salmon (Oncorhynchus keta) in the Nanaimo Estuary with the productivity of their principal food species. Chum were present in the estuary from March until June and the estuary population ranged up to 4.1 million in May 1975 and 2.4 million in April 1976. The average weight of chum was 0.66 g in 1975 and 0.65 g in 1976, and their rate of growth averaged ~6% body weight per day in both years. Food intake estimated by three independent methods ranged 4.4–18% body weight per day and was assumed to average 15% body weight per day. Annual fry production was 2381 kg in 1975 and 1122 kg in 1976. Food intake was 6184 kg in 1975 and 2815 kg in 1976. The principal dietary item in both years was harpacticoid copepods. In 1975 Harpacticus uniremis made up 50% of the diet overall, and >80% of the diet when fry were most abundant. The seasonal pattern of abundance of fry and H. uniremis on the estuary was the same, and the fry consumed most of the estimated production of H. uniremis. Juvenile chum production was potentially limited by food supply. Food chain dynamics were, therefore, important in the productivity of the chum population, but since both chum and its chief food were rare and ephemeral elements of the estuarine fauna, their interaction probably had little impact on the dynamics of the estuary as a whole. Key words: chum salmon, estuaries, food chains, populations, feeding rates

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