Multi-species larval fish growth model based on temperature and fluorometrically derived RNA/DNA ratios: results from a meta-analysis

Abstract

Weight-specific growth rate (G) and growth performance (the fraction of maximum growth realized, G pf ) are key demographic characteristics. The ratio of RNA/DNA (RD) can provide information on both G and G pf . Estimating G from RD in larval fish requires an adjustment for the activity of RNA at different temperatures. Based on a meta-analysis of published data, we present a general model for the relationship between G in marine fish larvae and fluorometrically derived RD and temperature (T), and suggest that this model can be used to estimate G in marine fish larvae. Several options for estimating G pf are also considered, including the use of a reference growth rate (G ref ). RDs of well-fed larvae appeared to be independent of water temperatures between 4 and 28°C, suggesting that any increase in growth rate with temperature was accomplished by increased activity rather than increased concentrations of RNA. However, for the best-fit meta-analysis RD-T-G model, the relationship between RD and G pf was temperature dependent for fish less than fully fed.KEY WORDS: RNA/DNA ratio · Growth · Larvae · Temperature effects · Nucleic acids · Fluorometric microplate assay · Multi-species meta-analysis Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 371: [221][222][223][224][225][226][227][228][229][230][231][232] 2008 among RD, temperature (T) and G (RD-T-G relationship). These calibration experiments require specialized rearing facilities, are costly, and labor intensive. Consequently, only a few calibrations are available for a very limited number of species (Table 1), thus hampering the widespread use of RD for estimating G in fish larvae.A variety of analytical methods have been used to estimate RNA and DNA concentrations in fish larvae. Because RD values are sensitive to the choice of procedures used, any meta-analysis of RD values from different laboratories has been problematic. This issue was addressed in a recent international intercalibration effort ) whereby fluorometrically derived RD estimates were standardized based on the slopes of the RNA and DNA standard curves (Berdalet et al. 2005). This standardization method opens up both the possibility of comparing fluorometrically derived RD among laboratories, and using RD-T-G relationships developed in other laboratories. Buckley (1984), using an UV method for analysis of RD, presented a RD-T-G calibration model based on data from larvae of 8 species of temperate marine fishes (Table 1), and suggested that there was a single relationship among RD-T-G that was independent of species. Although this general model has been used for several species, the conclusion that there is a single RD-T-G relationship in larvae of temperate marine fishes has not been further tested. Moreover, no general model based on the newer fluorometric methods has been published. To examine these and other issues, we propose the following hypotheses: (1) A single RD-T-G relationship can be used for all species of marine fish lar...

On the edge of death: Rates of decline and lower thresholds of biochemical condition in food-deprived fish larvae and juveniles

“…Biochemical condition (RD) is one of the most widely used growth indicators for marine fish early life stages (e.g., Buckley, 1984;Buckley et al, 2008;Chícharo and Chícharo, 2008;Clemmesen et al, 2003). Recent research has standardized this ratio (sRD) allowing comparison of measurements made in different laboratories .…”

“…Protein synthesis and somatic growth rates are no exception to this rule and various methods for generalization and comparison have been proposed. For example, Buckley et al (2008) reported that the best model describing instantaneous growth rates as a function of RD included a temperature interaction term (T × RD). Folkvord (2005) assessed intra-specific differences of larval cod from two distinct populations with the aid of a coupled size-temperature-growth model while Malzahn et al (2003) used degree-days to normalize the temperature dependence of somatic growth rates in North Sea houting larvae.…”

“…The nutritional condition of marine fish early life stages has been evaluated using the ratio of nucleic acids (RNA-DNA ratio, RD) for more than two decades (Buckley, 1984;Buckley et al, 2008). RNAs are essential for the biosynthesis of proteins and can vary depending on nutritional condition, while DNA levels in a cell remain fairly constant (Buckley et al, 1999;Bulow, 1987).…”

Response of Gilthead Seabream (Sparus aurata L., 1758) Larvae to Nursery Odor Cues as Described by a New Set of Behavioral Indexes

“…Negative values of the Preference Index indicate a preference for coastal water, while positive values indicate a preference for lagoon water. The vertical dashed line represents the 0.8 sRD critical level determined for gilthead seabream larvae using the equations of Buckley (1984) and Buckley et al (2008).…”

“…sRD ratios were converted to temperature-adjusted protein growth rates by applying the equation from Buckley (1984) and Buckley et al (2008), considering the average water temperature during the experiment (19.1 ± 1.1 • C). Thus, when larvae's protein growth rates are ≤ 0 or > 0, larvae are in poor and good nutritional condition, respectively (Robinson and Ware, 1988).…”