Comparing and Combining Effort and Catch Estimates from Aerial–Access Designs as Applied to a Large‐Scale Angler Survey in the Delaware River

Abstract

We used probability‐based aerial−access surveys to estimate effort, catch, and harvest of American shad Alosa sapidissima and striped bass Morone saxatilis by recreational anglers in the Delaware River and upper estuary in 2002. Sampling of anglers at access points and flights over the river were conducted weekly from mid‐March through October. Daily flight times were randomly selected; probabilities were proportional to the observed distribution of daily angler effort in a prior aerial−access survey (random count). Additional experimental flights were scheduled to occur at the time of day with expected peak effort (maximum count). Effort estimates derived from these maximum counts were more precise than estimates derived from the random flights, but the maximum‐count observations caused bias except when the daily count expansions were based on effort distributions from the concurrent access survey. The aerial and access surveys produced similar estimates of boat angler effort and little evidence of bias, but shore anglers were undercounted in the aerial survey. We maximized the precision and minimized bias in total effort estimates by combining the estimates of boat angler effort and shore angler access. An estimated sevenfold increase in the access survey sampling effort (at nearly five times the cost) would be required to achieve the same precision in the total effort estimate produced by the aerial–access survey. Effective stratification and the use of efficient model‐based estimators helped us to achieve the target precision of 20% in relative standard error (RSE) for estimated recreational catch of American shad (mean = 26,885 fish; RSE = 16%) and striped bass (mean = 47,671 fish; RSE = 15%). A single access survey during the American shad run would have required a 10‐fold increase in sampling effort to achieve the same precision in estimated catch at six times the cost of the complemented surveys.

Angler apps as a source of recreational fisheries data: opportunities, challenges and proposed standards

“…These data are collected directly from the fishery itself (e.g. Vølstad et al 2006) and involve complex methods that may not overcome significant bias (e.g. Strehlow et al 2012).…”

Recreational fisheries data requirements for monitoring catch shares

“…) and aerial‐access designs (Vølstad et al . ). A supplementary survey combines two or more contact methods where an additional survey provides double sampling to correct errors or deficiencies in another.…”

“…Boat‐based fishing has been the focus of many complementary survey designs (Vølstad et al . ; Hartill et al . ).…”

“…A complemented survey combines two or more contact methods for independent and mutually exclusive surveys, each being the complement of the other, that together provide a balanced whole. Boat-based fishing has been the focus of many complementary survey designs (Vølstad et al 2006;Hartill et al 2011). However, other studies use complementary survey designs for shore-based fishing with aerial-roving (Veiga et al 2010;Smallwood et al 2012) and aerial-access designs (Vølstad et al 2006).…”

Using posts to an online social network to assess fishing effort

“…Possible methods to collect effort-only data on a regional, or larger, scale include mail, telephone, and Internet surveys (Brown, 1991;Weithman, 1991), aerial surveys (Volstad et al, 2006), and bus-route count surveys (Jones and Robson, 1991). Although information on catch or harvest is often not collected during these * Corresponding author.…”