Implications of Channel Catfish Movement in an Internationally Managed System

1. Conflicts in mixed-use fisheries can arise when competing interest groups (e.g., commercial fishing, recreational fishing) target the same fish populations for provisioning services. How provisioning services of exploited fish populations are distributed among interest groups can be characterized as ecosystem service flows (ESF), where ESFs of a fishery are a function of the mobility of the targeted population, spatial distribution of the fishers, and the intensity of the fishing. 2. Informing fisheries management with ESF components is a promising way to develop appropriate policy for mixed-use fisheries but is challenging to incorporate for two reasons. First, fish movement studies used to assess the spatial characteristics of the fishery can vary by methodology (e.g., mark-recapture, telemetry), affecting the understanding of fish mobility and thus ESF. Secondly, the economic valuation of the provisioning services and the methodology used to assess value varies by interest group and by the size of the fish harvested. 3. We modeled the interaction of hypothetical exploitation scenarios and alternative movement methodologies for a long-lived, mobile fish species by using stage-structured Leslie matrix models. Our study organism, channel catfish Ictalurus punctatus, is a trophy sportfish in the Red River of the North, but also a species of commercial interest in Lake Winnipeg. The study system is composed of three different fishery types, a USA recreational fishery, a Canada recreational fishery, and a Canada commercial fishery that all utilize the channel catfish population for provisioning services. 67 4. Trophy stages of channel catfish were highly sensitive to exploitation and were typically depleted at or below a 0.30 exploitation rate. Depletion of populations and changes in stock structure affected subregions within the Red River system differently which resulted in competing strategies for each fishery from the perspective of economic valuation of harvests. 5. We found that recruitment from areas with greatest population size appeared to buffer aspects of harvest within regions and to some extent immediately adjacent regions. Movement, regardless of methodology, was critical in supporting exploitation for regions with low recruitment. The sustainability of exploiting highly mobile fish species from an ecosystem service flow perspective hinges on the ability of fisheries management organizations to incorporate spatial variability and understand the economic consequences of exploitation for competing interests. Introduction The science of ecosystem services is starting to embrace the concept that such services are not always bound to a single location (site-bound) (Costanza et al. 1997), but instead can flow and disperse (Bagstad et al. 2013). Burkhard et al. (2014) described ecosystem service flows as the spatially explicit routing of an ecosystem service source to beneficiaries. Ecosystem service carriers (e.g., matter, information, energy) are the means to provide benefits from the source locations to the use locations of the ecosystem that allow ecosystem service flows to function (Bagstad et al. 2013). Access to, and contact with, ecosystem service carriers that provide benefit to people are identified as provisioning benefits (Bagstad et al. 2013). Fish biomass has been identified as an “ecosystem service carrier” (Bagstad et al. 2013), but to our knowledge, very few fisheries are managed from an ecosystem service carrier perspective and seldom 68 managed from an ecosystem-based management standpoint (Holmlund and Hammer 1999; Pope et al. 2016). Instead, fisheries, and particularly inland fisheries, are often managed from a “one size fits all” approach that is reactive in design and often does not prioritize sustainability of the fisheries or resilience of the ecosystems (Carpenter and Brock 2004). The challenge associated with ecosystem-based management is that ecosystem service flows are typically derived from, or are a function of, open-access or common pool resources. Common pool services are often vulnerable to the “tragedy of the commons” phenomenon which can have large-scale effects on socio-ecological systems (Abbott and Wilen 2011). The vulnerability of common pool resources is driven by two characteristics: 1) rival, meaning the quantity of service decreases with use, and 2) non-excludable, meaning the resource can be used by anyone (Fisher et al. 2009). Fisheries are an example of a resource that is both rival and non-excludable, where the harvest of the resource depletes its services supplied and access to the fishery is often shared among multiple interest groups (Costello et al. 2008; McWhinnie 2009). Therefore, it is paramount to understand the mechanisms that influence the rival and non-excludable characteristics of inland fisheries, so management from an ecosystem service carrier perspective is more attainable. Ecosystem service flows are inherently spatial and the spatial scale on which an ecosystem service flow can function influences human-ecosystem interactions at both ecological and geopolitical scales (Hein et al. 2006). The inequity of an ecosystem service flow can introduce competing resource interests and thus generate conflicts (Bullock et al. 2011). Fish species that use large spatial-scales to complete their life histories (e.g. salmon migration) are more routinely being studied from a spatial perspective to inform fisheries and ecosystem 69 management initiatives but also to mitigate fishery conflicts (Cooke et al. 2013; Donaldson et al. 2014; Young et al. 2018). The provisioning services generated by a fishery encompasses some of the most contentious conflicts between fishing interests (e.g., commercial vs recreational) that can limit long-term sustainability prospects (Pauly et al. 2002; Worm et al. 2009; Spijkers et al. 2018). For example, recreational fishing has been identified as a contributor to declines in fish stocks (Coleman et al. 2004), but usually to a lesser extent than commercial fishing and is generally more localized to inland waters (Cooke and Cowx 2004; Winfield 2016). The variety of conflicts that may arise between the two practices poses challenges for fisheries management organizations when developing policy intended to govern each practice. These challenges may be especially true when each practice has contrasting perspectives on the extent to which harvest is allocated (or whether harvest should occur at all) and how much each practice contributes to the local economy (Arlinghaus and Cooke 2009). Recreational and commercial fisheries typically use fish stocks in a consumptive manner where catch, harvest, or both can be quantified and then scaled by economic metrics (Pereira and Hansen 2003). Fisheries management organizations now also incorporate valuation methods for commercial and recreational fisheries to bridge the gap of the economic asymmetries seen in mixed-use fisheries. Understanding the spatial extent and intensity of harvest provides fisheries management organizations the foundation to assess fisheries from an economic perspective and an opportunity to enact evidence-based decisions for spatially-explicit policy. The successful implementation of ecosystem-based management for fisheries depends on understanding the spatial extent of socio-ecological interactions (Pikitch et al. 2004; Katsanevakis et al. 2011; Nunes et al. 2015; Ansong et al. 2017). Management of freshwater fish 70 species may be particularly difficult in ecosystems with competing harvest demands across multiple political jurisdictions (Pracheil et al. 2012). Adoption of biotelemetry methods into fisheries science are revealing more complex spatial behaviors of both marine (Wilson et al. 2015; Torre et al. 2017) and freshwater fish species (Pellett et al. 1998; Pracheil et al. 2009; Hrenchuk et al. 2017) suggesting that management organizations need to incorporate the spatial scale on which a given fish stock’s life-history operates (Olsen et al. 2012; Pracheil et al. 2012). Similarly, uncovering how connectivity of inland ecosystems provides movement corridors for different life-stages of fish is critical in understanding fundamental population dynamics (Spurgeon et al. 2018). There are very few examples of fisheries management that have examined the nexus of mixed-use fisheries using both spatial ecological information and valuation approaches (Abbott 2014). Furthermore, exploration of alternative management approaches from an ecosystem-service flow perspective of inland fisheries are also absent in the literature, but some marine fisheries examples exist (Martin et al. 2016; Owuor et al. 2017). Exploring how one’s understanding of movement can influence the outcomes associated with fisheries management scenarios is critical in informing fisheries policy. The Red River of the North-Lake Winnipeg system (Minnesota and North Dakota, United States of America; Manitoba, Canada) is one inland system that holds a fish species (channel catfish Ictalurus punctatus) that exhibits large-scale spatial movements and is included in a mixed-use fishery. We set out to incorporate a comprehensive evaluation of alternative management approaches for an ecosystem service flow perspective using channel catfish that may be subjected to varying management regimes depending on their specific location within the system. The goal of this study was to present an assessment of the channel catfish fishery 71 concerning movement, exploitation, and valuation as a means to initiate understanding the implications of potential fisheries management scenarios. We specifically asked: 1) how do different movement methodologies interact with exploitation to affect the allocation of ecosystem service flows (status quo evaluation), 2) what are the regional impacts of exploitation on stock structure, especially the trophy portion of the ecosystem service flow, 3) how does a long-lived, slow-growing fish