Efficacy of harvest and minimum size limit regulations for controlling short-term harvest in recreational fisheries B. T. VAN POORTEN, S.P. COX & A. B. COOPER School of Resource and Environmental Management, Simon Fraser University, Burnaby, BC, Canada Abstract It is important to consider the potential effectiveness of regulations for reducing total harvest levels when developing fishery management plans. A random forest (RF) modelling approach was used to examine how changing per-angler harvest or minimum size limit regulations affected sport fishery harvest in US Atlantic coast recreational fisheries. Harvest limits per angler (i.e. bag limits) were typically high initially and subsequently reduced, whereas almost half of minimum length limits were initially below the length-at-maturity and subsequently increased. Across most fisheries examined, extreme reductions in harvest limits (e.g. from unlimited to catch-and-release) were largely ineffective at limiting total fishery harvest. Increasingly restrictive minimum length limits caused a greater average harvest reduction than per-angler harvest limits. Some regulation changes were associated with higher angling effort and thus increased harvest, which suggests that when effort cannot be constrained, more direct harvest limitations should be considered. KEYWORDS: harvest, harvest limit, management regulation, minimum size limit, random forest, recreational angling. Introduction A growing recreational angling sector increases the total contribution of recreational fisheries to many local econo- mies (Bartholomew & Bohnsack 2006), prompting calls for reallocating more total allowable catch to the recrea- tional sector (Mcphee et al. 2002; Ihde et al. 2011). It is therefore not surprising that recreational harvest represents a growing source of mortality for a large number of mar- ine fish species, often overtaking mortality rates caused by commercial fisheries (Ihde et al. 2011; Coleman et al. 2004; Cooke & Cowx 2004). In developed countries, commercial fishery catch and effort are typically moni- tored as part of the requirement for owning a licence through a combination of portside monitoring and on-board observers. In principle, such close and timely monitoring of commercial fisheries allows for reasonably tight control of total harvest and thus fishing mortality. Recreational fisheries, on the other hand, are much more difficult to monitor for total catch, harvest and effort because reporting is generally not required of licence hold- ers and access points for observers are diffuse across the coastal landscape (Cooke & Cowx 2006). Although agen- cies such as the US National Marine Fisheries Service (NMFS) routinely conduct recreational fishery surveys, it is often not possible to analyse the data, make in-season regulation changes and enforce those regulations fast enough to close fisheries when total allowable recreational catch is exceeded. These difficulties with output harvest controls typically force agencies to rely on regulating angling efficiency (i.e. input controls) to a point where it is unlikely that allowable catches will be exceeded given the estimated number of anglers in a fishery (Coleman et al. 2004). Although specific regulatory objectives vary among fisheries (Radomski et al. 2001), recreational angling regulations are generally aimed at limiting angler efficiency and/or limiting harvest on sensitive size-classes and age-classes of fish populations (Scrogin et al. 2004; Dawson & Wilkins 1981; Homans & Ruliffson 1999). Therefore, for our purposes, we define a short-term (i.e. a few years) decline in harvest as the mark of an effective management regulation. In both marine and freshwater recreational fisheries, two of the most common fishing regulations are size Correspondence: Brett T. van Poorten, British Columbia Ministry of Environment, 315-2202 Main Mall, Vancouver, British Columbia, Canada (e-mail: Brett.vanPoorten@gov.bc.ca) doi: 10.1111/j.1365-2400.2012.00872.x © 2012 Blackwell Publishing Ltd Fisheries Management and Ecology, 2013, 20, 258–267 258 Fisheries Management and Ecology