Validation of close‐kin mark–recapture (CKMR) methods for estimating population abundance

Under embargo until: 2020-06-181. Knowing how many individuals there are in a population is a fundamental problem in the management and conservation of freshwater and marine fish. We compare abundance estimates (census size, Nc) in seven brook trout Salvelinus fontinalis populations using standard mark–recapture (MR) and the close‐kin mark–recapture (CKMR) method. Our purpose is to validate CKMR as a method for estimating population size. 2. Close‐kin mark–recapture is based on the principle that an individual's genotype can be considered a “recapture” of the genotypes of each of its parents. Assuming offspring and parents are sampled independently, the number of parent–offspring pairs (POPs) genetically identified in these samples can be used to estimate abundance. We genotyped (33 microsatellites) and aged c. 2,400 brook trout individuals collected over 5 consecutive years (2014–2018). 3. We provide an alternative interpretation of CKMR in terms of the Lincoln– Petersen estimator in which the parents are considered as tagging the offspring rather than the offspring “recapturing” the parents. 4. Despite various sources of uncertainty, we find close agreement between standard MR abundance estimates obtained through double‐pass electrofishing and CKMR estimates, which require information on age‐specific fecundity, and population‐ and age‐specific survival rates. Population sizes (N) are estimated to range between 300 and 6,000 adult individuals. Our study constitutes the first in situ validation of CKMR and establishes it as a useful method for estimating population size in aquatic systems where assumptions of random sampling and thorough mixing of individuals can be met.acceptedVersio

Marine habitat use and feeding ecology of introduced anadromous brown trout at the colonization front of the sub-Antarctic Kerguelen archipelago

Abstract In 1954, brown trout were introduced to the Kerguelen archipelago (49°S, 70°E), a pristine, sub-Antarctic environment previously devoid of native freshwater fishes. Trout began spreading rapidly via coastal waters to colonize adjacent watersheds, however, recent and unexpectedly the spread has slowed. To better understand the ecology of the brown trout here, and why their expansion has slowed, we documented the marine habitat use, foraging ecology, and environmental conditions experienced over one year by 50 acoustically tagged individuals at the colonization front. Trout mainly utilized the marine habitat proximate to their tagging site, ranging no further than 7 km and not entering any uncolonized watersheds. Nutritional indicators showed that trout were in good condition at the time of tagging. Stomach contents and isotope signatures in muscle of additional trout revealed a diet of amphipods (68%), fish (23%), isopods (6%), and zooplankton (6%). The small migration distances observed, presence of suitable habitat, and rich local foraging opportunities suggest that trout can achieve their resource needs close to their home rivers. This may explain why the expansion of brown trout at Kerguelen has slowed

Validation of close‐kin mark–recapture (CKMR) methods for estimating population abundance

1. Knowing how many individuals there are in a population is a fundamental problem in the management and conservation of freshwater and marine fish. We compare abundance estimates (census size, Nc) in seven brook trout Salvelinus fontinalis populations using standard mark–recapture (MR) and the close‐kin mark–recapture (CKMR) method. Our purpose is to validate CKMR as a method for estimating population size. 2. Close‐kin mark–recapture is based on the principle that an individual's genotype can be considered a “recapture” of the genotypes of each of its parents. Assuming offspring and parents are sampled independently, the number of parent–offspring pairs (POPs) genetically identified in these samples can be used to estimate abundance. We genotyped (33 microsatellites) and aged c. 2,400 brook trout individuals collected over 5 consecutive years (2014–2018). 3. We provide an alternative interpretation of CKMR in terms of the Lincoln– Petersen estimator in which the parents are considered as tagging the offspring rather than the offspring “recapturing” the parents. 4. Despite various sources of uncertainty, we find close agreement between standard MR abundance estimates obtained through double‐pass electrofishing and CKMR estimates, which require information on age‐specific fecundity, and population‐ and age‐specific survival rates. Population sizes (N) are estimated to range between 300 and 6,000 adult individuals. Our study constitutes the first in situ validation of CKMR and establishes it as a useful method for estimating population size in aquatic systems where assumptions of random sampling and thorough mixing of individuals can be met

Atlantic Sturgeon Spatial and Temporal Distribution in Minas Passage, Nova Scotia, Canada, a Region of Future Tidal Energy Extraction.

In the Bay of Fundy, Atlantic sturgeon from endangered and threatened populations in the USA and Canada migrate through Minas Passage to enter and leave Minas Basin. A total of 132 sub-adult and adult Atlantic sturgeon were tagged in Minas Basin during the summers of 2010-2014 using pressure measuring, uniquely coded, acoustic transmitters with a four or eight year life span. The aim of this study was to examine spatial and seasonal distribution of sturgeon in Minas Passage during 2010-2014 and test the hypothesis that, when present, Atlantic sturgeon were evenly distributed from north to south across Minas Passage. This information is important as tidal energy extraction using in-stream, hydrokinetic turbines is planned for only the northern portion of Minas Passage. Electronic tracking data from a total of 740 sturgeon days over four years demonstrated that Atlantic sturgeon used the southern portion of Minas Passage significantly more than the northern portion. Sturgeon moved through Minas Passage at depths mostly between 15 and 45 m (n = 10,116; mean = 31.47 m; SD = 14.88). Sturgeon mean swimming depth was not significantly related to bottom depth and in deeper regions they swam pelagically. Sturgeon predominately migrated inward through Minas Passage during spring, and outward during late summer-autumn. Sturgeon were not observed in Minas Passage during winter 2012-2013 when monitoring receivers were present. This information will enable the estimation of encounters of Atlantic sturgeon with in-stream hydrokinetic turbines

Summary of coded acoustic tag models used during Atlantic sturgeon tagging project in Minas Basin during the summers of 2010, 2011, 2012 and 2014 (n = 132).

<p>All models supplied by Vemco Inc., Halifax, NS, Canada.</p

Summary of yearly detections of acoustically tagged Atlantic sturgeon that occurred in Minas Passage during 2010–2014 (n = 132).

<p>Summary of yearly detections of acoustically tagged Atlantic sturgeon that occurred in Minas Passage during 2010–2014 (n = 132).</p

Depth box plots (Line = median, box = 25 and 75% quartiles, whiskers = SD and dots = outliers) distribution for acoustically tagged Atlantic sturgeon recorded on the Ocean Tracking Network, Minas Passage Line, Minas Passage, Nova Scotia, Canada, totals for years 2010–2014.

<p>Depth box plots (Line = median, box = 25 and 75% quartiles, whiskers = SD and dots = outliers) distribution for acoustically tagged Atlantic sturgeon recorded on the Ocean Tracking Network, Minas Passage Line, Minas Passage, Nova Scotia, Canada, totals for years 2010–2014.</p

Results of OTN range test experiment calculated by Sanderson et al. (in preparation).

<p>Probability of detection of Atlantic sturgeon tagged with V16 acoustic tags (158 db, 75 sec average transmission interval) passing the OTN Minas Passage Line. Individual receivers are represented by blue lines with left hand side representing the south (first blue peak = receiver MPS012) and right side (last blue peak = receiver MPS001). Solid black line represents the probability of a tagged sturgeon being detected by at least one of the receivers. Probability of being detected by at least one receiver is nearly identical for the north and south sections of the line, with a small reduction in probability of detection in the middle.</p

Sturgeon day distribution for acoustically tagged Atlantic sturgeon recorded on the Ocean Tracking Network Minas Passage Line, Minas Passage, Nova Scotia, Canada, totals for years 2010–2014.

<p>Sturgeon day distribution for acoustically tagged Atlantic sturgeon recorded on the Ocean Tracking Network Minas Passage Line, Minas Passage, Nova Scotia, Canada, totals for years 2010–2014.</p

The Minas Basin is the north-eastern portion of the inner Bay of Fundy (A); Minas Passage, links Minas Basin to the rest of the Bay of Fundy (B).

<p>The Minas Basin is the north-eastern portion of the inner Bay of Fundy (A); Minas Passage, links Minas Basin to the rest of the Bay of Fundy (B).</p