Growth, production and bioenergetics of brown trout in upland streams with contrasting riparian vegetation

Abstract

1. A series of laboratory-based equations on trout growth and bioenergetics developed by J.M. Elliott were applied to data collected for brown trout (Salmo trutta L.) under field conditions in Co. Mayo, Western Ireland. Fish were collected by electrofishing eight upland streams with contrasting riparian vegetation; grassland, open canopy and closed canopy deciduous. 2. Stream temperatures, one of the main influencing factors on fish growth and energetics, did not differ significantly between riparian types. 3. Observed growth rates were lower than the predicted maximum growth rates and were not influenced by riparian vegetation type. Growth ranged between 0.66% day )1 for 0 + trout to 0.08% day )1 for 2 + trout. 4. Production estimates showed no clear difference between riparian vegetation types over the growing season. 5. Fish densities and biomass tended to be greater in closed canopy streams particularly in summer. 6. Actual ration sizes calculated for trout were similar to the ration required for maintenance metabolism and were only 45-63% of the maximum potential rations. Although there was an ontogenetic increase in ration size with increasing fish age, the proportion of ration available for growth (i.e. the difference between actual and maintenance rations) did not differ between age classes but was greatest in summer. 1+ and 2+ trout show greatest ration available for growth in grassland streams. 7. Trout growth did not differ between riparian vegetation types but did vary seasonally with greatest attainment in summer. Growth was limited in the present study possibly due to combined effects of reduced prey available to fish and low stream temperatures reducing metabolic requirements. In such food limited systems, terrestrial invertebrate energy subsidies could have significant benefits to brown trout growth, production and bioenergetics.

The Stream Biome Gradient Concept: factors controlling lotic systems across broad biogeographic scales

“…Riparian cover is hypothesized to influence fish or amphibian occurrence and abundance in Northern California (Welsh et al 2005) and Japan (Inoue andNunokawa 2005, Nakamura andYamada 2005). However, Dineen et al (2007) found that riparian cover did not influence stream water temperature in for-ested Northern Ireland, and speculated that increased terrestrial subsidies in forested streams were important in maintaining growth of trout. Saunders and Fausch (2007) showed that intensive grazing by livestock reduced riparian vegetation and led to decreased input of terrestrial invertebrates, thereby reducing foraging opportunities for trout in mountain grassland streams.…”

Ontogenetic and spatial variations in brown trout habitat selection

“…In salmonids, spatio-temporal variations in population abundance and production are closely related to differences and changes in physical habitat conditions Lobó n-Cerviá & Rincó n 2004). Further, together with other essential biotic and abiotic factors, habitat quality and quantity influence many population traits such as survival (Harvey et al 2005;Lobón-Cerviá 2007), growth (Harvey et al 2005;Dineen et al 2007) or migration rates (Belanger & Rodriguez 2002), as well as pervasive biological processes like self-thinning (Lobó n-Cerviá 2008), that affect population dynamics. Habitat selection is perceived as an adaptive complex behaviour faced by organisms at the individual level, but shapes many key biological processes whose patterns emerge at higher organisation levels (Grimm & Railsback 2005).…”

What are the effects of wooded riparian zones on stream temperature?

“…Ten studies were identified following full text assessment, and from which data could be retrieved (see Additional file 4) [34][35][36][37][38][39][40][41][42][43]. These studies were in: New Zealand (3), UK (2), USA (2), Ireland (1), Spain (1) and Denmark (1).…”