Endurance at intermediate swimming speeds of Atlantic mackerel, Scomber scombrus L., herring, Clupea harengus L., and saithe, Pollachius virens L.

Abstract

Endurance and swimming speed were measured in mackerel, herring and saithe when they were induced by the optomotor response to swim at prolonged speeds along a 28-m circular track throughstillwater ina 10-mdiametergantry tank. Themaximumsustainedswimmingspeed(U,,, was measurcd as body lengths per second (H.L.S -') for each species and for saithe of direrent size groups. Hcrring with Lfm% of 4.06 B . L .~ ' (25.3 cm, 13.5' C) were the fastest, mackerel U,, was 3 . 5 1 3 .~~ ' (33cm. I1.7"C) and saithe (14.4"C) showed a size effect where Urn, at 25cm was 3.5 R.L.S ' and at 50cm 2.2 B . L .~ I . When swimming at speeds higher that U,,, all three species showed reduced endurance as speed increased. How thecurved track reduces the swimming speed is discussed.

Pursuit plunging by northern gannets (Sula bassana) "feeding on capelin (Mallotus villosus)"

“…The downward speed of a bird after a few seconds of the start of the dive, when birds are assumed to use wings for movements rather than the momentum of the plunge dive, reached speeds of up to 2.4 m during 2 s (equivalent to 1.2 m s 71 ). This dive speed is slightly faster than the maximum sustained swimming speed of herrings (Clupea harengus) (1.03 m s 71 ), mackerels (Scomber scombrus) (1.16 m s 71 ) (He & Wardle 1988) and capelins (1.16 m s 71 ) (W. A. Montevecchi and G. Davoren, unpublished results), all of which are important prey of northern gannets in the North-West Atlantic (Montevecchi & Myers 1996). The maximum burst speeds of mackerel can exceed 5 m s 71 but probably last no more than 10 s (He 1993), which is much shorter than the maximum dive durations of northern gannets.…”

Determining the severity of skin injuries of red mullet, Mullus barbatus (Actinopterygii: Perciformes: Mullidae), inflicted during escape from trawl codend

“…Although previous experiments have been conducted towards the end of the summer (with water temperatures of 21-25°C), the water temperature was~13°C in our study. Low water temperature may affect the fish behaviour, such as decreasing swimming speed and endurance (He and Wardle, 1988) and also the escapement ability of fish from the codend. Therefore, it is likely that seasonal factors, such as water temperature (that was 8-10°C higher in the previous experiments), fish condition, and size structure of the captured population, have been responsible for the relatively large mortality rate reported in this study.…”

Migration patterns in Norwegian spring-spawning herring: why young fish swim away from the wintering area in late summer

“…These 3 school types were excluded to reduce bias: Schools with a mean swimming speed above 2.0 m s -1 , as the sustained swimming speed of herring of the observed size is below this value (He & Wardle 1988); school registrations lasting less than 21 pings, due to low data precision during short registration periods (Hafsteinsson & Misund 1995); and schools where the vessel heading changed by more than 20°during the recording period, as large changes in vessel direction distorted the apparent school movements.…”

“…He & Wardle 1988, Misund & Aglen 1992, Hafsteinsson & Misund 1995. Despite small fish sizes, migration speed in sub-area A was high, suggesting that herring rapidly left areas with low prey availability.…”