Comparison of the body proximate compositions of juvenile bronze gudgeon (Coreius heterodon) and largemouth bronze gudgeon (C. guichenoti) in the upstream region of the Yangtze River

Luo et al. SpringerPlus 2013, 2:75 http://www.springerplus.com/content/2/1/75 a SpringerOpen Journal RESEARCH Open Access Comparison of the body proximate compositions of juvenile bronze gudgeon (Coreius heterodon) and largemouth bronze gudgeon (C. guichenoti) in the upstream region of the Yangtze River Yiping Luo*, Qingda Huang, Yurong Zhang, Shuting Liu and Wen Wang Abstract The body proximate compositions were assessed in juvenile Coreius heterodon and C. guichenoti from the upstream of the Yangtze River. The migratory C. guichenoti has a higher lipid content (FAT) than the residential C. heterodon. FAT of C. guichenoti showed an interesting pattern of increase, where FAT increased up rapidly and then leveled off as body mass (M) increased above 6.5 g, suggesting that the lipid concentration reaches an upper limit of deposition. In both species, FAT of the smaller individuals was lower than protein content (PRO), but FAT increased more rapidly than PRO as the fish grew. This indicates that more energy was allocated to protein synthesis than lipid in the smaller fish, with an energy allocation shift from protein synthesis to lipid storage as the fish grew. Strong relationships between both FAT and energy content (E) and water content (WAT) were found in both species, suggesting strong predictive power for future application. However, different models for the two species should be used to predict FAT or E by WAT. Keywords: Body size, Water content, Lipid content, Energy content, Bronze gudgeon Introduction Fish body proximate compositions are important parameters used in fish ecology and physiology, and are related to feeding status (Sogard and Spencer 2004; Blake et al. 2006; Ali et al. 2008), seasons (Jonsson et al. 1997; Berg and Bremset 1998; Robards et al. 1999), habitat (Anthony et al. 2000; Dempson et al. 2004), and body size (Deegan 1986; Shearer et al. 1994; Jonsson and Jonsson 1998, 2003). Changes in the proportions of water, lipid, protein, and ash, result in variation of energy storage in the fish body. This might influence performance related to species fitness, such as the chance of the successful reproduction, survival during seasonal food shortages, and avoidance of predation. In many fish species, the contents of lipid, protein, and energy increase as the fish grows, accompanied by a decrease in water content (Shearer et al. 1994; Jonsson and Jonsson * Correspondence: Key Laboratory of Freshwater Fish Reproduction and Development (Southwest University), Ministry of Education, Chongqing 400715, China 1998, 2003; Anthony et al. 2000). Data for more species needs to be documented. Previous studies have found strong relationships between water content or dry mass content and other proximate compositions (Jonsson and Jonsson 1998, 2003; Pangle and Sutton 2005; Hartman and Margraf 2008). Water content is relatively simple to measure, therefore it can be used as an easy indicator to estimate concentrations of lipid, protein, and energy (Van Pelt et al. 1997; Hartman and Margraf 2008). However, prediction models can vary among species (Hartman and Margraf 2008). It is of interest to examine whether a common prediction model is possible for some closely related species. The bronze gudgeon, Coreius heterodon, and the largemouth bronze gudgeon, Coreius guichenoti, are two related species of wild freshwater fish in China. The two species have many similar biological characteristics, such as body shape, feeding habits and growth parameters. Both are of economic importance, and are the main species found in the mid- and upstream parts of the Yangtze © 2013 Luo et al.; licensee Springer. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Luo et al. SpringerPlus 2013, 2:75 http://www.springerplus.com/content/2/1/75 River, accounting for 34% (C. heterodon) and 24% (C. guichenoti) of total species abundance (Yang et al. 2012). Their population dynamics (Yang et al. 2012), population genetics (Liao et al. 2007; Zhang and Tan 2010), reproductive ecology (Liu et al. 1990) and respiratory physiology (Luo and Wang 2012) have been reported in previous studies. C. heterodon resides in a limited river area for its whole life, while C. guichenoti has a special migratory-like behavior. Juvenile C. guichenoti live in the area of Chongqing for around 3 to 4 years, then gradually move 600–1000 km up to the Jinsha River (the upper reaches of Yangtze River above Yibin City) and are resident in Jinsha River for their whole lives (Liu et al. 1990; Ding, 1994). Adult fish spawn in the lotic and cooler water from April to July each year and the eggs drift downstream into the Yangtze River (Liu et al. 1990). Long distance movement is an energy expensive process (Hinch and Bratty 2000; Kiessling et al. 2004; Caudill et al. 2007), therefore it could be hypothesized that the fish store sufficient energy before starting to move upstream. However, energy accumulation and growth in the juveniles of this fish are unclear. Therefore, it is of interest to study how the body chemical compositions of juveniles of this species change as their body mass increases. Previous studies have shown that long distance migratory species have greater energy storage and faster deposition of lipids with body growth (Jonsson and Jonsson 1998; Jonsson and Jonsson 2005). Comparison of the body chemical compositions of the migratory C. guichenoti and the residential C. heterodon could provide new data for closely related species with different life-history strategies. We hypothesize that C. guichenoti has a higher body lipid content of C. heterodon. This study aims to provide energy prediction models for juvenile C. guichenoti and C. heterodon in the upstream part of the Yangtze River and to determine how the proximate compositions change with body growth in the closely related species with different life-histories. Page 2 of 6 content (FAT,%) was determined by ether extraction using Soxhlet. Ash content (ASH,%) was determined by combustion at 550°C for 7 hours. Energy content (E, kJ g-1) was calculated based on 23.6 kJ g-1 of protein and 39.5 kJ g-1 of lipid (Brett and Groves 1979). Small individuals of similar size (body length difference within 2 mm) were pooled to obtain sufficiently large samples for chemical analysis (15 g wet mass). The mean value of the body length, the body mass, and the chemical composition of each pool was used as one sample. The final sample sizes were 53 for C. heterodon and 118 for C. guichenoti. We used SPSS 11.0 (SPSS Inc., Chicago, IL, USA) for statistical analyses. The relationships between M and chemical composition were described using power curve estimation. The relationships between WAT and other proximate compositions were described using linea (...truncated)