Estimates of Effective Number of Breeding Adults and Reproductive Success for White Sturgeon

Abstract

Accurate estimates of the number of adults contributing to offspring (Ns), effective breeding number (Nb), and individual adult contributions to recruitment are required for recovery planning for endangered White Sturgeon Acipenser transmontanus populations, many of which are suffering from prolonged periods of recruitment failure. We show that genetic techniques can be used to characterize important features of White Sturgeon reproductive ecology in large rivers where census data are extremely difficult to obtain. We used 12 microsatellite loci and likelihood‐based pedigree analysis to estimate Ns, Nb, number of kin groups (Nk), and individual reproductive success of White Sturgeon contributing to viable eggs and larvae collected in the upper Columbia River in each of 2 years. Estimated mean ±SD annual Ns was 121.5 ± 34.7, Nb was 86.5 ± 10.6, and Nk was 73.5 ± 17.3. Large variations in estimates of Ns, Nb, and Nk were observed between three spawning areas, in which one spawning site representing 61% of total adult spawning population. Variation in adult reproductive success was observed within and among sites. Estimated mean ±SD individual spawning duration was 1.9 ± 1.1 d, and number of mates per adult was 2.9 ± 2.5, which also varied spatially and temporally. Based on age of collected eggs and larvae, number of spawning days ranged from 5 to 19 d between years and among sites. Genetically derived estimates of Ns were lower but generally concordant with empirical estimates of available spawners (Nc), based on sex ratios and maturation staging of adults captured independently (Ns/Nc ratio = 0.683). Results increase our understanding of White Sturgeon reproductive ecology and recruitment and allow projections of cohort levels of genetic diversity. Similar data can be applied to recovery planning and aquaculture programs for this and other species of conservation concern. Received January 6, 2014; accepted May 28, 2014

If you build it, will they come? Spawning habitat remediation for sturgeon

“…Quantifying stagebased survival may not be possible, however, systematic monitoring using standard techniques such as egg mats, benthic sampling and drift nets, can be used to estimate egg deposition (Caroffino, Sutton, Elliott, & Donofrio, 2010;Roseman et al, 2011a), egg loss (Johnson et al, 2006b), yolk-sac larvae survival (Johnson et al, 2006b;McAdam 2012) and larval dispersal (Crossman & Hildebrand, 2014;Dumont et al, 2011;Roseman et al, 2011a). Developmental staging of eggs or larvae allows the backcalculation of spawning time (Jay et al, 2014). Ontogenetic drift patterns (McAdam, 2011) and larval quality indicators (Baker et al, 2014) also offer potential biological indicators.…”

“…While the main target of habitat remediation is sturgeon, the effects (positive or negative) on other species also warrant consideration. For example, substrate remediation may also benefit freshwater mussels (Haag and Williams, ), macro invertebrates (McManamay et al., ; Merz and Chan, ), salmonids (Jensen et al., ) and other lithophilic spawning fish (e.g., Jennings et al., ; Romanov et al., ). The potential for responses by non‐target species to overwhelm responses from target species (Pine et al., ) must be seriously considered, and supports the need for broader monitoring programs.…”

“…Use of restored spawning habitat provides a straightforward metric of remediation effectiveness, with indicators of spawning ranging from the presence, density, and depositional pattern of eggs, to the number of spawners and their sex ratios. For example, recent genetic studies provide a means to estimate the number of spawning adults from collected wild progeny(Jay et al, 2014;Manny et al, 2015). Direct adult counts (see Rupert River case study) and DIDSON acoustic camera (Bray,Crossman, Martel, & Johnson, 2011) have also be used to detect spawning adults.…”

Variance in Reproductive Success is Driven by Environmental Factors, not Mating System, in Bonytails

“…; Jay et al. ). Mating behaviors, such as spatially or temporally synchronous spawning, can also make populations vulnerable to exploitation and predation (Rowe and Hutchings ) and hence can impact species conservation.…”

“…Knowledge of the reproductive ecology of bony fishes in general-and endangered species in particular-is vital for implementation of effective management and conservation programs. For example, interannual variability in levels of recruitment and contribution of breeding adults to offspring production can significantly impact genetic diversity and abundance (e.g., Hedgecock 1994;Bekkevold et al 2002;Jay et al 2014). Mating behaviors, such as spatially or temporally synchronous spawning, can also make populations vulnerable to exploitation and predation (Rowe and Hutchings 2003) and hence can impact species conservation.…”