Stocking history, biological characteristics, and status of Atlantic salmon (Salmo salar) on Prince Edward Island

This paper compiles information on Atlantic salmon (Salmo salar) in Prince Edward Island (PEI), for use in a review by the Committee on the Status of Endangered Wildlife in Canada. Stocking of Atlantic salmon in PEI waters began in 1880, and has continued to the present time, with some interruptions. Prior to the 1970s, most reproductive material used to stock PEI waters was of PEI origin. In the 1970s, a management objective was set to create early salmon runs by using early-run broodstock of mainland origin, or local early-run broodstock which was likely descended at least in part from mainland fish. At least 37 million salmon were released to PEI waters during 1880 to 1960. Original PEI salmon populations were dominated by fall runs of large (>63 cm fork length) fish. These run-time and size characteristics persist in salmon populations in small PEI rivers. In larger PEI rivers where stocking has been intense, early-run small (<63 cm) salmon form a major, often dominant, component of returning adults. Accounts in the early historical period indicate that salmon were present throughout PEI. At least 71 PEI rivers probably offered sufficient habitat to support salmon populations. Of these, 55 rivers have historic or modern records of having been occupied by salmon. Surveys conducted in 2000 to 2002 and in 2007 to 2008 found salmon in 28 and 22 rivers, respectively. Populations in many rivers are very small and face the likelihood of extirpation if current trends continue. Threats to salmon populations in PEI include stream sedimentation, blockages by beaver dams, artificial impoundments, pesticide kills, competition with rainbow trout, and stream blockages by improperly installed culvert

The status of Atlantic salmon (Salmo salar) on Prince Edward Island (SFA 17) in 2011

Prince Edward Island, Salmon Fishing Area 17, is part of the southern Gulf - Gaspé Designatable Unit which COSEWIC assessed as Special Concern in 2010. Atlantic salmon probably occupied about 71 PEI rivers at the time of European contact. Rivers containing salmon fell to 28 in 2000-2002 and to 22 in 2007-2008, with salmon presence detected in one additional river in 2011. Original salmon populations were largely late-run and multi-sea-winter, but stocking fish of mainland origin has led to early run components in seven PEI rivers. Reported harvest in aboriginal Food, Social, and Ceremonial fisheries were 0-1 fish per year in 2009-2011 (only one of two licenced groups provided harvest information in 2011). Recreational salmon angling is permitted in all PEI rivers, but salmon in small rivers receive de facto protection from angling because seasons close on 15 September, before fish return to these rivers. Salmon fishing is permitted up to 31 October in parts of larger rivers which have early-run components. Recreational angling has been catch-and-release since 2009. Estimated mortalities in the angling fishery due to catch-and-release mortality (assumed to be 3%) were 1- 4 fish per year in 2009-2011. Angler card surveys indicate that fishing effort, small salmon kept, and small and large salmon released have followed declining trends since the mid-1990s. Total conservation requirements for current salmon rivers (4,668,586 eggs) are based on all habitat types in these rivers, including habitat blocked by dams. Egg deposition was estimated from historic biological characteristics and redd counts, using a redd:female spawner ratio (3.357) measured in a single year in the West River, PEI. Total estimated egg deposition in current salmon rivers is 67.7% of requirements for these rivers. Estimated deposition exceeds requirements in six rivers. Total conservation requirements for all 71 probable current and historic salmon rivers on PEI are 10,565,273 eggs. Estimated total egg deposition is 29.9% of this total. Atlantic salmon on PEI are negatively affected by sedimentation, blockages to upstream passage due to artificial and beaver dams, excessive water temperatures and low dissolved oxygen levels caused by some dams, pesticide inputs, and competition with rainbow trout. Fishing mortality from aboriginal fishery harvests and from angling is currently low and probably has little impact on salmon populations. Major sources of uncertainty in this assessment include low sample sizes in angler card surveys, use of historic rather than current data on biological characteristics, and use of a redd:spawner ratio measured at only one site in one yea

Spontaneous mirror symmetry breaking in the limited enantioselective autocatalysis model: abyssal hydrotermal vents as scenario for the emergence of chirality in prebiotic chemistry

The emergence of chirality in enantioselective autocatalysis for compounds unable to transform according to the Frank-like reaction network is discussed with respect to the controversial limited enantioselectivity (LES) model composed of coupled enantioselective and non-enantioselective autocatalyses. The LES model cannot lead to spontaneous mirror symmetry breaking (SMSB) either in closed systems with a homogeneous temperature distribution or in closed systems with a stationary non-uniform temperature distribution. However, simulations of chemical kinetics in a two-compartment model demonstrate that SMSB may occur if both autocatalytic reactions are spatially separated at different temperatures in different compartments but coupled under the action of a continuous internal flow. In such conditions, the system can evolve, for certain reaction and system parameters, toward a chiral stationary state; that is, the system is able to reach a bifurcation point leading to SMSB. Numerical simulations in which reasonable chemical parameters have been used suggest that an ade- quate scenario for such a SMSB would be that of abyssal hydrothermal vents, by virtue of the typical temper- ature gradients found there and the role of inorganic solids mediating chemical reactions in an enzyme-like role. Key Words: Homochirality Prebiotic chemistry