Habitat fragmentation in the Fraser River watershed : implications for salmonid habitat remediation and management

Habitat fragmentation has been implicated in broad declines of Pacific salmon and trout populations in the Pacific Northwest of North America. Dams are often considered to be the largest driver of fragmentation. However, small-scale barriers like floodgates, weirs and culverts can have significant negative impacts on stream habitat. In British Columbia (BC), Canada, an estimated 135,000 - 200,000 culverts act as barriers to fish passage, making them a major issue for salmonids and a target for restoration. Despite barrier culverts being one of the leading anthropogenic causes of stream fragmentation globally and a frequent target of restoration efforts, the efficacy of these interventions and their conformance with best practices has rarely been examined. Effective planning of these restoration efforts is often hindered by incomplete barrier inventories and uncertainty about where best to perform restoration. I addressed these issues by performing two complementary studies. I first performed a 'post-treatment' audit of culvert barrier remediations in southcentral BC through an examination of current physical attributes at 15 retrofit and 15 replacement sites and scored sites based on the BC culvert fish passage assessment and on best practice guidelines for stream crossings in BC. I then used two modelling approaches to evaluate historical habitat availability, how barriers potentially prevent Chinook and Coho salmon migrations, and the role of barrier remediation in enhancing habitat accessibility in the South Thompson watershed of BC. At barrier remediation sites, 80% of retrofits and 20% of replacements were classified as fish passage barriers, and conformance with best practices was at most 80% at any site. I modelled that Chinook and Coho salmon historically had access to 3600 km and 3400 km of stream length, and these habitats are currently impacted by 1955 barriers. These results show that fragmentation of salmon habitat is a widespread issue, potentially exacerbated by predicted barriers, and that poor conformance may be hindering the effectiveness of remediation actions.Forestry, Faculty ofGraduat

High overexploitation risk due to management shortfall in highly traded requiem sharks

Most of the international trade in fins (and likely meat too) is derived from requiem sharks (family Carcharhinidae), yet trade in only two of the 56 species is currently regulated. Here, we quantify catch, trade, and the shortfall in national and regional fisheries management (M-Risk) for all 56 requiem shark species based on 831 assessments across 30 countries and four Regional Fisheries Management Organizations (RFMOs). Requiem sharks comprise over half (60%) of the annual reported global Chondrichthyan catch with most species (86%) identified in the international fin trade. Requiem sharks are inadequately managed by fisheries, with an average M-Risk of half (50%) of an ideal score, consequently 70% of species are threatened globally. The high catch and trade volume and shortfall in management of these iconic species require worldwide fisheries management for sustainable catch, supported by full implementation of CITES regulations for international trade of this newly listed family

Guitarfishes are plucked: Undermanaged in global fisheries despite declining populations and high volume of unreported international trade

Some sharks and rays are subject to fisheries catch and international trade regulations. However, the Guitarfishes (family Rhinobatidae) are a highly threatened group with minimal regulations. The true volume of Guitarfishes in international trade is underestimated and masked by substantial underreporting of catch and the use of broad commodity codes for traded products. Here, we begin to document the extent of trade by collating international trade information for Guitarfishes that have not readily been documented in trade, possibly due to poor resolution of molecular genetic markers. We also assess the shortfall in fisheries management (M-Risk) for all species of Guitarfish based on 99 assessments across 28 countries. Globally, Guitarfishes are inadequately managed, with an average M-Risk of 45% of an ideal score, resulting in 76% of species being threatened globally. The high and unregulated catch and trade volume, paired with the management shortfalls, require global integrated improvement in fisheries management, supported by regulating international trade to sustainable levels