Using Limited Data to Identify Optimal Bag and Size Limits to Prevent Overfishing

Abstract

Bag and size limits are commonly used in recreational fisheries management, but these regulations are often treated as separate management tools. This effectively overlooks how bag and size limits can be simultaneously used to achieve multiple management outcomes (e.g., reduce exploitation, prevent overfishing, maximize angler acceptance, etc.). Our objectives were to combine data‐limited stock assessment methods with an angler catch simulation and a yield‐per‐recruit model to assess the effectiveness of bag and size limits to decrease exploitation rates and improve the spawning potential ratio (SPR). We then applied these methods to the Kipawa Lake Walleye Sander vitreus fishery that has experienced overfishing and poor fishing quality. Using data‐limited assessment methods, the exploitation rate was estimated at 0.45 (95% CI = 0.32–0.59) and the population was overfished (mean SPR = 0.06; 95% CI = 0.02–0.13). Bag limits significantly reduced total harvest when extremely restrictive (i.e., reduced to one fish per angler from the current limit of six), but changes in bag limits alone were not sufficient to prevent overharvest because SPR remained below 0.35. Size limits could be used to prevent overharvest with narrow harvest slots (up to a 14‐cm slot range with a minimum harvestable size greater than 32 cm) or large minimum size limits (>52 cm) at the current bag limit of six. When bag limits were reduced to one or two fish per day, harvest windows could be 3–13 cm larger and minimum length limits could be 3–12 cm lower to prevent overharvest. This analysis outlines a relatively simple and effective method that can be applied using data commonly collected in annual agency surveys to predict which regulatory combinations can be used to prevent overharvest, reduce exploitation rates, and maximize angler satisfaction and acceptance of regulations. Finally, the data and model code are included in the Supplement and can be easily applied to other data limited fisheries.

Saving large fish through harvest slots outperforms the classical minimum‐length limit when the aim is to achieve multiple harvest and catch‐related fisheries objectives

“…Other models have accounted for some of these processes, but these models were calibrated to specific species (e.g. northern pike, Esox lucius , Esocidae, Arlinghaus et al, ; brown trout, Salmo trutta , Salmonidae, Ayllón et al, ; catfishes of the genus Ictalurus , Ictaluridae, Steward, Long, & Shoup, ; lake trout Salvelinus namaycush , Salmonidae, Lenker, Weidel, Jensen, & Solomon, ; or walleye, Sander vitreus , Percidae, Moreau & Matthias, ), and the results thus lacked generality. Importantly, none of the cited studies have systematically asked which harvest policy is optimal given a spectrum of fishery objectives.…”

Goodbye to “Rough Fish”: Paradigm Shift in the Conservation of Native Fishes

“…Possession limits need to be broadly considered as a native fish conservation tool and might be in line with possession limits applied to other managed species (e.g., often twice the daily bag limit). While a blunt tool, bag and possession limits can be effective at curbing overfishing and improving population structure (Rypel 2015; Oele et al 2016; Moreau and Matthias 2018). Agencies must simultaneously be careful with such instruments, lest harvest limits restrict access to fisheries and food for disadvantaged communities.…”

Data-limited stock assessment of red mullet (Mullus barbatus) from the Iskenderun Bay, the north-eastern Mediterranean Sea

“…Data-limited stock assessment methods have been getting increased attention (Cortés and Brooks 2018;Moreau and Matthias 2018;Turan 2021). Here, the data-limited stock assessment based on length-frequency data is effectively estimated the stock size and status of M. barbatus off the Iskenderun Bay coasts.…”