Large-scale variation in seasonal swimming patterns of plaice in the North Sea

Abstract

We examined the mid-water swimming activity of 139 mature female plaice Pleuronectes platessa L. These were tagged with electronic data storage tags (DST1s and DST3s) to test whether swimming at different times of the year differed among areas of the North Sea with average tidal current velocities ranging from fast (West), to intermediate (East), to slow (North). Longer swimming duration and more tidal activity were predicted for the western group, where fast-flowing tidal currents allow efficient selective tidal stream transport. Individual depth data were converted into binary records representing either swimming or resting; repeated patterns of swimming were analysed according to cycle-length frequencies. Most swimming occurred during expected times of migration and spawning (October to March). Plaice infrequently spent >5 h in mid-water, and rarely left the sea-bed during summer. DST1 tagged plaice (West only) spent the longest times swimming (p > 0.001), but there was no significant effect of Area for DST3s (all areas), suggesting that swimming plays an important behavioural role in migration in addition to transport between feeding and spawning areas. Tidal patterns of activity occurred in all 3 sub-stocks, predominantly during the migratory period (albeit at a significantly lower frequency in the North). These data provide one of few examples where the annual behaviour patterns of a fish stock have been recorded across a large part of its geographical range. The results have important implications for understanding the energetics of fish migration and the availability of demersal stocks to capture by commercial and survey vessels

Listening In on the Past: What Can Otolith δ18O Values Really Tell Us about the Environmental History of Fishes?

“…C). Except for active vertical movement during migration and spawning, the tagged plaice in the current study were largely at, or close to, the seabed [64] . As such, baseline knowledge of bottom temperature and salinity could generate δ 18 O "isoscapes" [65] as a predictor of potential marker efficacy for this species.…”

Indirect effects of bottom fishing on the productivity of marine fish

“…Studies of fish movement suggest that some demersal fish species move relatively short distances while foraging, compared with their longer seasonal migrations (Dunn and Pawson ; Hunter et al . ). Recent studies that have sampled fish diets and benthic prey resources on spatial scales that are relevant to fish feeding (Smith et al .…”

“…As a result, the mechanisms illustrated by the models of fish feeding are likely to be attenuated by spatial variability. Studies of fish movement suggest that some demersal fish species move relatively short distances while foraging, compared with their longer seasonal migrations (Dunn and Pawson 2002;Hunter et al 2009). Recent studies that have sampled fish diets and benthic prey resources on spatial scales that are relevant to fish feeding (Smith et al 2013;Johnson et al 2015) do find differences in diet and growth across disturbance gradients.…”

Validation of otolith δ18O values as effective natural tags for shelf-scale geolocation of migrating fish

“…Righton et al 2016). Because plaice, like other flatfish, spend much of their life on or close to the seabed (Hunter et al 2009), the risk of confounding effects due to vertical movements with geographical migrations is limited. Other potential candidates include cod Gadus morhua, which can spend protracted periods of time resting on the seabed (Righton et al 2001).…”