Energy allocation in polymorphic Brown Trout

Abstract

1. To evaluate differences in energy allocation to gonadal development of resident and anadromous Brown Trout, Salmo trutta, we analysed tissue composition and energy contents of adults of the two morphs from three small streams in southernmost Norway. Somatic energy per unit mass of anadromous spawners (5·0 ± 0·6 kJ g–1 wet weight) was 1·1 times that of the residents. This difference was chiefly due to a 1·4 ‐times higher lipid content in anadromous (4·9 ± 1·5%) than resident trout. The somatic protein and carbohydrate contents per unit mass were higher in resident than anadromous fish. 2. Somatic energy content per unit mass increased linearly with body length in resident but not anadromous fish. This increase was due to a significant increase in lipid content with fish size in resident contrary to anadromous trout. 3. The mass‐specific energy content of the ovaries was higher for residents (8·4 ± 0·4 kJ g–1 wet weight) than anadromous (7·81 ± 0·5 kJ g–1 wet weight) trout. This was due to higher lipid and protein contents per unit mass in resident than anadromous females. In males, no similar differences between morphs were found (5·9 ± 0·8 kJ g–1 wet weight). The mass‐specific energy content of the ovaries was c. 1·4 higher than that of the testes, mainly caused by a 2·3–2·6 higher lipid content per unit mass of eggs. 4. The mean gonadosomatic index (kJ %) was higher in anadromous (34·0 ± 9·4) than resident (28·6 ± 5·5) females, but not in males (≈ 3%). In females, but not in males, gonadal energy increased linearly with increasing somatic energy of the fish. 5. Female gonadal energy at corresponding somatic energies was higher than that of males. On average, the energetic investment in gonads relative to soma of first‐time spawners in the year of maturation was estimated at 11% in males and 67% in females.

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“…Lipid content of brown trout egg in the present study was 9.3%, in accordance with wild lake trout egg (9.1-9.9%) from Lake Michigan (Czesny et al, 2012) and it was slightly higher than wild brown trout egg (7.8-8.6%) from some Norwegian streams (Jonsson and Jonsson, 1997). The latter study reported that the energetic investment in gonads to relative soma in female brown trout during the maturation was estimated at 67%.…”

Phenotypic differences between the sexes in the sexually plastic mangrove rivulus fish (Kryptolebias marmoratus)

“…It is well established that maintaining ovarian tissue is energetically expensive whereas maintaining testicular tissue is relatively inexpensive (Hayward and Gillooly, 2011;Jonsson and Jonsson, 1997;Yong and Grober, 2013; but see Olsson et al, 1997). Maintaining ovarian tissue has negative impacts on individual survival, growth, immunocompetence and future reproductive efforts (Bergeron et al, 2011;.…”

“…Predators can intercept male courtship signals (Taylor and Ryan, 2013) and competing aggressively to acquire mating opportunities can be energetically costly and carry high risks of injury (Brick and Jakobsson, 2002;Neat et al, 1998). Females accrue costs by supporting energetically expensive ovarian tissues Hayward and Gillooly, 2011;Jonsson and Jonsson, 1997;Yong and Grober, 2013). To sustain current reproductive efforts, females may allocate energy away from somatic growth, fat storage or future reproduction .…”

“…Based on Minamimoto et al's (2006) previous findings, we predicted that males would have higher KT and E2 concentrations than hermaphrodites, while testosterone and cortisol would not vary between the sexes. Comparisons of the energetic demands for maintaining ovarian and testicular tissues often reveal ovarian tissue as more costly than testicular tissue (Hayward and Gillooly, 2011;Jonsson and Jonsson, 1997;Yong and Grober, 2013; but see Olsson et al, 1997). In rivulus, the hermaphrodite ovotestis is dominated by ovarian tissue and has small pockets of testicular tissue.…”

A Comparison of Relative Weight and Nutritional Status among Four Fish Species in Two Impoundments

“…Nutritional condition may be suppressed for a considerable period after the reproductive season. The greater onus is likely to be on females (Craig 1977, Jonsson andJonsson 1997).…”