Effects of location errors on estimates of dredge catchability from depletion based methods

Discriminating between high- and low-quality field depletion experiments through simulation analysis

“…The implementation of a definitive measure of dredge efficiency for analyzing shellfish survey data substantially improves the estimation of abundance. Commonly, depletion experiments are used to estimate gear efficiency and population density for sessile and sedentary species in a target area (Leslie and Davis, 1939;Skalski et al, 1983;Lasta and Iribarne, 1997;Gedamke et al, 2005;Wilberg et al, 2013). These experiments are conducted by dredging over the same area and tracking the decline in catch of a target organism per dredge tow.…”

“…Other dredge efficiency quantification methods, such as use of an underwater camera in between dredge tows, have also been used (Chai et al, 1992;Ragnarsson and Thórarinsdóttir, 2002;Morson et al, 2018). For a range of dry dredges, estimates exist for their efficiency for catching epibenthic animals, including oyster (Powell et al, 2007;Morson et al, 2018), clam (Pezzuto et al, 2010), crab (Vølstad et al, 2000;Wilberg et al, 2013), and scallop (Lasta and Iribarne, 1997;Beukers-Stewart and Beukers-Stewart 1 ) species. By comparison, highly efficient hydraulic dredges are the primary gear type used to capture infaunal clam species (Da Ros et al, 2003;Hauton et al, 2007;Gilkinson et al, 2005;Meseck et al, 2014).…”

“…1). As is often the case, estimates of dredge efficiency varied widely between individual experiments (Vølstad et al, 2000;Powell et al, 2007;Hennen et al, 2012;Wilberg et al, 2013;Morson et al, 2018). Very little is known about how environmental and sampling conditions influence the efficiency of a hydraulic dredge, factors that are likely the source of variation between experiments.…”