Estimating Fish Exploitation and Aquatic Habitat Loss across Diffuse Inland Recreational Fisheries

<div><p>The current state of many freshwater fish stocks worldwide is largely unknown but suspected to be vulnerable to exploitation from recreational fisheries and habitat degradation. Both these factors, combined with complex ecological dynamics and the diffuse nature of inland fisheries could lead to an invisible collapse: the drastic decline in fish stocks without great public or management awareness. In this study we provide a method to address the pervasive knowledge gaps in regional rates of exploitation and habitat degradation, and demonstrate its use in one of North America’s largest and most diffuse recreational freshwater fisheries (Ontario, Canada). We estimated that 1) fish stocks were highly exploited and in apparent danger of collapse in management zones close to large population centres, and 2) fish habitat was under a low but constant threat of degradation at rates comparable to deforestation in Ontario and throughout Canada. These findings confirm some commonly held, but difficult to quantify, beliefs in inland fisheries management but also provide some further insights including 1) large anthropogenic projects greater than one hectare could contribute much more to fish habitat loss on an area basis than the cumulative effect of smaller projects within one year, 2) hooking mortality from catch-and-release fisheries is likely a greater source of mortality than the harvest itself, and 3) in most northern management zones over 50% of the fisheries resources are not yet accessible to anglers. While this model primarily provides a framework to prioritize management decisions and further targeted stock assessments, we note that our regional estimates of fisheries productivity and exploitation were similar to broadscale monitoring efforts by the Province of Ontario. We discuss the policy implications from our results and extending the model to other jurisdictions and countries.</p></div

The proportion of individual project sizes in numbers (left column) and in their cumulative sum of potential impact area to fish habitat (right column) from all the permits under the <i>Fisheries Act (1985)</i> granted in Ontario in 2005 to developers.

<p>We present two scenarios that represent a lower and upper bound to our estimates of fish habitat protected for each permit: Scenario 1) Letters of Advice represent generally small projects, and Scenario 2) Letters of Advice represent projects that without the <i>Fisheries Act (1985)</i> would have impacted standard project-specific areas of fish habitat (i.e. HADDs).</p

The spatial distribution of the surplus yield remaining following a fishing season in 2005 delineated by Ontario’s Fisheries Management Zones.

<p>The spatial distribution of the surplus yield remaining following a fishing season in 2005 delineated by Ontario’s Fisheries Management Zones.</p

The spatial distribution of the road coverage (grey lines) and distribution of projects (black dots) approved under the <i>Fisheries Act (1985)</i> delineated by Ontario’s Fisheries Management Zones.

<p>The spatial distribution of the road coverage (grey lines) and distribution of projects (black dots) approved under the <i>Fisheries Act (1985)</i> delineated by Ontario’s Fisheries Management Zones.</p

The spatial distribution of the yields of accessible fisheries in 2005 delineated by Ontario’s Fisheries Management Zones.

<p>The spatial distribution of the yields of accessible fisheries in 2005 delineated by Ontario’s Fisheries Management Zones.</p

The spatial distribution of the area of fish habitat protected using the average of the lower and upper bounds of our estimates in 2005 delineated by Ontario’s Fisheries Management Zones.

<p>The spatial distribution of the area of fish habitat protected using the average of the lower and upper bounds of our estimates in 2005 delineated by Ontario’s Fisheries Management Zones.</p