Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide

Abstract

Threadfin shad Dorosoma petenense density and biomass of four Puerto Rico reservoirs - seasonal differences and comparison among temperate and tropical reservoirs.

Abstract

Threadfin shad, Dorosoma petenense (Günther, 1867) are the primary prey species for sport fish in many temperate and tropical reservoirs. However, quantification of density or biomass for threadfin shad is rare in the literature and limited in geographic scope. The objectives of this paper were to report seasonal threadfin shad biomass estimates from tropical reservoirs where this species has been introduced, and to compare tropical threadfin shad populations to temperate reservoirs where this species is native. Considerable variability was observed among Puerto Rico reservoirs for biomass (F3,210=14.8, P<0.0001), with estimates ranging from 2.0 to 32.2 kg/ha. Within reservoirs, biomass fluctuated as much as 24-fold between seasonal sampling events (CV ranged 51-126%). Comparison to data from temperate reservoirs in the southern United States suggested that Puerto Rico reservoirs may have threadfin shad populations that are generally less dense with less biomass, calling into question the previous assumption that prey limitation was not an issue in tropical systems. This research also indicates that threadfin shad populations are under-evaluated in most temperate systems, and that current threadfin shad sampling strategies of single sampling event per year may not be adequate to provide accurate characterization of threadfin shad populations.