Feeding of larval blue whiting and Atlantic mackerel: a comparison of foraging strategies

Abstract

Fish larvae employ different feeding strategies depending on area and season of spawning and hatching of larvae. Feeding and growth of larvae of blue whiting Micromesistiuspoutussou and mackerel Sconiher scomhrus from Porcupine Bank and the Celtic Shelf Break, west of Ireland, were compared based on prey concentrations in the environment and larval feeding behaviour. Both species were adapted to different environmental conditions. The mesopelagic blue whiting spawned in oceanic water that was well mixed. It was characterized by low production and low prey densities with minimum prey densities <1.0 organism 1-'. Larvae of the Atlantic mackerel hatched later in the season in more productive water that was well stratified. Prey densities in the mackerel environment reached up to 100 1 ~ I . Blue whiting larvae displayed a rather random distribution in the water column. Mackerel larvae <7 mm standard length (L,) were concentrated above the thermocline, while larvae >7 mm traversed the thermocline into deeper layers. Mackerel larvae >5 mm L, displayed marked cannibalism, exceeding 70'X~ Daily ration calculated on the basis of gut contents was rather low in both species: between 2.6 and 50% in blue whiting, but only 0.6 to S.4Y0 in mackerel. The results are discussed in relation to the respective environment both species encounter during their early larval life. 'C 1997 The Fisheries Society of the British Irlea

Feeding of the Brycon cephalus, Triportheus elongatus and Semaprochilodus insignis (osteichthyes, characiformes) larvae in Solimões/Amazonas River and floodplain areas.

“…Fish larvae consumption by fish larva is rare, and it is usually linked to large mouthed larvae, such as Scomber scombrus (Hillgruber et al, 1997) and Scomberomorus niphonicus (Shoji et al, 1997). However, large mouth is not synonymous to a behavior of feeding on other fish larvae.…”

Small-scale patterns in distribution and feeding of Atlantic mackerel ( Scomber scombrus L.) larvae in the Celtic Sea with special regard to intra-cohort cannibalism

“…The different estimates for the two larval size classes appear justified, because mackerel larvae switch at 5.0 mm SL to piscine prey (Hillgruber et al 1997), which are likely to need more time for digestion. Based on these digestion times, daily ration estimates were calculated using the Elliott and Persson (1978) …”

“…The diet of mackerel larvae has been described in several papers; however, most studies investigated the western populations of the North Atlantic (Sette 1943;Lett 1980;Peterson and Ausubel 1984;Ware and Lambert 1985;Fortier and Villeneuve 1996), while little information exists about the eastern Atlantic populations, namely larvae from the North Sea (Lebour 1920;Last 1980;Grave 1981) and larvae from the European shelf edge -the western stock (Hillgruber et al 1997;Conway et al 1999). To date no consecutive sampling effort directed at Atlantic mackerel of the western stock as the primary target has been published.…”

“…In the eastern Atlantic, the highest densities of Atlantic mackerel (Scomber scombrus) larvae appear in the Celtic Sea and above the Celtic Shelf in May/June (O'Brien and Fives 1995), where the larvae hatch at the onset of the secondary productivity maximum (Colebrook 1986) into a stratified water column (Hillgruber et al 1997). The diet of mackerel larvae has been described in several papers; however, most studies investigated the western populations of the North Atlantic (Sette 1943;Lett 1980;Peterson and Ausubel 1984;Ware and Lambert 1985;Fortier and Villeneuve 1996), while little information exists about the eastern Atlantic populations, namely larvae from the North Sea (Lebour 1920;Last 1980;Grave 1981) and larvae from the European shelf edge -the western stock (Hillgruber et al 1997;Conway et al 1999).…”

“…Instead of ingesting increasing numbers of small prey items, however, mackerel larvae appear to attempt to utilize a more efficient food source, namely fish larvae. All but one study (Last 1980) targeting Atlantic mackerel larvae observed piscivorous and cannibalistic foraging behavior (Lebour 1920;Grave 1981;Peterson and Ausubel 1984;Ware and Lambert 1985;Fortier and Villeneuve 1996;Hillgruber et al 1997;Conway et al 1999). However, disagreement still exists as to the nature of this feeding mode, i.e., is it a density-dependent behavior (Fortier and Villeneuve 1996) or a feeding mode that the larvae are predisposed to by morphological adaptations (Tanaka et al 1996;Conway et al 1999).…”