Growth and survival rates of dispersing free embryos and settled larvae of pallid sturgeon (Scaphirhynchus albus) in the Missouri River, Montana and North Dakota

Abstract

We released nearly 1.0 million 1-day post-hatch (dph) and 5-dph pallid sturgeon (Scaphirhynchus albus) free embryos in the Missouri River on 1 July 2019 and sequentially captured survivors at multiple sites through a 240-km river reach to quantify daily growth and survival rates during the early life stages. Genetic analysis was used to assign captured fish to released family lots and known ages. Growth rate was similar (0.74–0.75 mm day−1) between the 1- and 5-dph age groups during the 3–4-day dispersal period when water temperature averaged 16.8 °C. Daily survival rate was 0.64 during 1–4 dph for the original 1-dph age group and 0.80 during 5–7 dph for the original 5-dph age group. Total survival during free embryo dispersal (hatch to 9 dph) was estimated as 0.0437. The transition from dispersing as free embryos to settling as benthic larvae was verified for fish originally released as 5 dph. Growth of settled larvae was quantified with a Gompertz model through 75 dph (9 September; 112 mm) when water temperature was 18.8–21.0 °C in the rearing areas. Settled larvae had an estimated daily survival rate of 0.96, and estimated total survival during 9–75 dph was 0.0714. This study provides the first empirical survival estimates for pallid sturgeon early life stages in natural settings and is one of few studies reporting similar information for other sturgeon species. Applications of this work extend to pallid sturgeon restoration programs where population models are being developed to predict recruitment potential and population responses to river management alternatives.

Diet composition and overlap of larval pallid sturgeon and shovelnose sturgeon from the upper Missouri River, USA

“…We sampled for sturgeon larvae in 8 river bends, of which 4 were located at the UTC site and 4 were located at the DTC site. Sampling for pallid sturgeon larvae at the 8 bends targeted fish that had settled as benthic larvae following the 1 July 2019 release at rkm 2739.0 of nearly 772 000 free embryos at 1 dph and 201 000 free embryos at 5 dph (Braaten et al 2022). Sampling also targeted wild-produced shovelnose sturgeon larvae originating from spawning events in the Missouri River and Yellowstone River .…”

“…Larvae with SNP genotypes consistent with pallid sturgeon were genotyped at 19 microsatellite loci (McQuown et al 2000) and analyzed following the protocols of Jordan et al (2019) to confidently assign each individual as pallid sturgeon or shovelnose sturgeon. For individuals identified as pallid sturgeon, a genetic parental analysis (DeHaan et al 2008) was used to assign the pallid sturgeon larvae to parental stocks used to produce the 1 and 5 dph released free embryos (Braaten et al 2022).…”