The feeding behaviour of cultured and wild Atlantic salmon, Salmo salar L., in the Louvenga River, Kola Peninsula, Russia

Abstract

An underwater survey was conducted in the Louvenga River to investigate the behaviour and distribution of juvenile Atlantic salmon, Salmo salar L., and the adaptation of cultured fish to the natural environment. The food and feeding habits of 34 wild and 44 cultured parr released from the Kandalaksha hatchery were also studied. The cultured salmon fed mostly in the bottom 15 cm of the water column in current velocities of 0.2e0.35 m s À1 . In contrast to wild fish, when cultured fish moved away from these areas and into areas with higher current velocities (average speeds of 0.52 m s À1 ) and lower drift density (2.66 particles m À3 ), they did not show a tendency to return to slower moving water. The diet of cultured parr was made up of benthic invertebrates (20%), terrestrial insects (32%), and drift items (33%), but these proportions were different in the diet of wild parr (2%, 24%, and 67%, respectively), with drift items predominating. The mean quantity of food per stomach indicated that the wild parr were feeding more actively than cultured parr. Invertebrates made up 3% of items in the drift, with the remaining 97% being exuvia of aquatic and terrestrial insects, algae, and various plant remains. Poor quality food items were found in 13% and 25% of the stomachs of wild and cultured parr, respectively, demonstrating that the cultured parr were less able to differentiate food items in the water column and made 20e30% more false feeding attempts than wild fish. The cultured parr were also more aggressive in terms of the frequency of aggressive interactions and reacted to each other at greater distances than wild fish. Thus, wild parr were able to optimize their feeding conditions by choosing habitats with preferred sizes of food items, higher densities of drift items, and current velocities that allowed them to maintain station and to feed more effectively. Conversely, cultured parr usually occupied suboptimal areas.

The biogeography of the atlantic salmon (Salmo salar) gut microbiome

“…Although poor in absolute numbers of OTUs (that is, richness), diversity estimates from returning adults were not significantly different from juveniles, suggesting a fairly even frequency distribution of those OTUs present. Dietary complexity in juvenile salmonids could explain rich associated microbial assemblages (Orlov et al, 2006). Meanwhile physiological disturbances and fasting in migratory phases (smolt and returning adults) could underlie reduced community stability with respect to corresponding non-migratory phases (that is, parr and marine adults, Figure 1b).…”

“…Growth, development and migration in anadromous S. salar involves a radical shift across an ecological and trophic spectrum (Jacobsen and Hansen, 1999;Orlov et al, 2006). Accompanying the physiological, behavioural and dietary adaptations necessary to cope with transition between freshwater and marine environments (McCormick et al, 2013), significant and potentially adaptive shifts in host-associated microbiota might be expected.…”

Not all lineages are equally invasive: genetic origin and life-history in Atlantic salmon and brown trout acclimated to the Southern Hemisphere

“…In the wild, domestic salmon exhibit lower fitness than wild salmon and aquaculture escapes can endanger natural populations compromising their viability (Clifford et al 1998;McGinnity et al 1998McGinnity et al , 2003McGinnity et al , 2009. Domestication encompasses genetic changes in life-history traits, which can be subjected to directional selection in farm conditions (Fleming and Einum 1997;Hindar et al 2006) and also in behavioral components such as aggressiveness, mate choice and others (Fleming and Gross 1993;Fleming et al 2000Fleming et al , 2002MignonGrasteau et al 2005;Orlov et al 2006;Castillo et al 2008). As an indicator of such altered behavior, individuals of domestic origin provide most hybrid crosses between Atlantic salmon and brown trout in southern Europe (Castillo et al 2008).…”

Appetite and Feed Intake

“…For example, compared to hatchery-reared fish from unselected lines, coho salmon (Oncorhynchus kisutch) selected for rapid growth over many generations ingest more food, grow faster and grow more efficiently; fish of the selected line seem to be particularly efficient at using lipids for energy, sparing protein for growth (Figure 7.20;Neely et al 2008). Considering the post-release effects of domestication and captive rearing, wild juvenile Atlantic salmon have fuller stomachs than do hatchery-reared fish soon after release, though this difference is short-lived (Orlov et al 2006) and no differences are reported between domesticated and wild brown trout (Johnsson et al 1996). Finally, captive-bred butterfly splitfins (Ameca splendens) are less likely to feed and more likely to fight than are wild fish (Kelley et al 2006).…”