Environmentally induced spatio‐temporal variations in the fecundity of brown trout Salmo trutta L.: trade‐offs between egg size and number

Abstract

1. Resident brown trout Salmo trutta in the Esva River basin (north Spain) live in a patchy environment with tracts of riparian forest or meadow along stream banks. This study assessed whether the reproductive traits of brown trout from four contrasting sites reflected site‐specific factors. 2. Length at maturity (10.5–11 cm of 1 + individuals) was the same in the four sites examined but slowest growers in slow‐growing sub‐populations delayed maturity for 1 year relative to fast‐growing fish. The analysis of monthly variations in egg size and number suggest that two ‘decisions’ in two consecutive years are required to complete spawning. The first concerns the number of eggs, determined when trout are still 0 +, and the second concerns egg size. 3. At three sites, egg size and number did not differ significantly between years but highly significant interannual variations were apparent at another site. Fish length was the major determinant of egg size and number at all sites but for any given length, brown trout at sites where the fish exhibited higher growth rates spawned more, but smaller, eggs than those at slow‐growing sites. This spatial pattern was identical to the temporal pattern exhibited by trout at another site. The combination of temporal (year‐to‐year) and spatial (between rivers) variations in egg size and number showed a significant negative correlation, supporting the operation of a trade‐off between these two traits. 4. The trade‐off between egg size and number seems to be determined by site‐specific factors, with slow‐growing trout at sites which are fully covered by canopy spawning fewer, but larger, eggs than fast‐growers in unshaded sites.

Effect of Culture Conditions on Reproductive Traits of Brown Trout Salmo Trutta L.

“…Stronger relationships with the standard length were found for the farmed fish and correlations for the spawner weight were similar for both populations. Similar relationships of the reproductive parameters with the size of brood fish have been found by many authors (MCFADDEN et al, 1965;BAGENAL, 1969;OJANGUREN et al, 1996;L´ABÉE-LUND and HINDAR, 1990;LOBON-CERVIA et al, 1997).…”

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“…The results of the present study are consistent with the previous findings that, in salmonids, both egg size and fecundity correlate positively with maternal size (Fleming and Gross, 1990;Lobon-Cervia et al, 1997;Rollinson and Hutchings, 2010). Studies have shown that larger eggs give rise to larger juveniles, and that larger juveniles exhibit increased survival, competitive ability, swimming performance, growth and overall fitness (Blaxter, 1988).…”

“…Several energy-related mechanisms can influence the amount of energy allocated to gonads during a reproductive cycle and thus the number and size or quality of eggs that are spawned (Van Winkle et al, 1997). Most studies addressing maternal provisioning and egg quality in fish consider various measures of egg and alevin size, such as diameter, wet mass, dry mass (e.g., Hutchings, 1991;Lobon-Cervia et al, 1997;Olofsson and Mosegaard, 1999;Berg et al, 2001;Hendry et al, 2001;Heinimaa and Heinimaa, 2004), the yolk mass and the yolk sphere diameter and volume (Heming and Buddington, 1988) and biochemical composition (Lahnsteiner et al, 1999;Keckeis et al, 2000;Berg et al, 2001;Yanes-Roca et al, 2009). Enzyme activity has been used less frequently as an indicator of egg quality (Lahnsteiner et al, 1999;Lahnsteiner et al, 2001).…”

Variations in egg characteristics of ruffe Gymnocephalus cernua inhabiting brackish and freshwater environments

“…This result suggests that larger eggs may be an adaption to increased salinity in BW environments. There is a trade-off between egg size and fecundity: Fish that produce larger offspring lose in their overall fecundity and thereby in their potential maternal fitness (Smith and Fretwell 1974;Elgar 1990;Lobon-Cervia et al 1997). Because of that, either larger offspring (from larger eggs) must have greater fitness and survival in BW to compensate mother's greater energetic investment per offspring (coupled with loss in fecundity) or larger eggs are physiologically crucial at the certain embryonic developmental stages for successful reproduction in saline environment.…”