DOI: 10.5061/dryad.nk98sf7qq
title: Dataset for: Spatial and environmental effects on Coho Salmon life-history trait variation

description: Adult size, egg mass, fecundity and mass of gonads are affected by
 trade-offs between reproductive investment and environmental conditions
 shaping the evolution of life-history traits among populations for widely
 distributed species. Coho salmon Oncorhynchus kisutch have a large
 geographic distribution and different environmental conditions are
 experienced by populations throughout their range. We examined the effect
 of environmental variables on female size, egg size, fecundity, and
 reproductive investment of populations of Coho Salmon from across British
 Columbia using an information theoretic approach. Female size increased
 with latitude and decreased with migration distance from the ocean to
 spawning locations. Egg size decreased with average intragravel
 temperature during incubation, migration distance, in larger rivers, but
 increased in rivers that were lake headed. Fecundity increased with
 latitude, warmer temperature during the spawning period, and river size,
 but decreased in rivers that were lake headed compared to rivers with
 tributary sources. Gonadal somatic index increased with latitude and
 decreased with migration distance. Latitude of spawning grounds, migratory
 distance and temperatures experienced by a population, but also hydrologic
 features – river size and headwater source – are influential in shaping
 patterns of reproductive investment, particularly egg size. The lack of an
 effect of latitude on egg size suggest that local optima for egg size may
 drive the positive relationship between egg number and latitude – a
 pattern that is partially off-set by larger female size and gonadal
 somatic index with latitude.
description: Data were obtained from Fisheries and Oceans Canada (FOC) and
 included mean female size (post orbital hypural length
 [<i>L</i><sub>POH</sub>] most commonly or fork
 length [<i>L</i><sub>F</sub>]), mean egg mass
 (<i>M</i><sub>egg</sub>), and mean fecundity
 (<i>F</i>) for each year data were available. Additional
 life-history data on mean <i>F</i> and
 <i>L</i><sub>POH</sub> were also obtained from
 Fleming and Gross (1990) for Big Qualicum River, Black Creek, and Quinsam
 River populations, and <i>L</i><sub>POH</sub> from
 Meldrum et al. (2017) and references therein for Black Creek.
 For female size, measurements for
 <i>L</i><sub>F</sub> were converted to
 <i>L</i><sub>POH</sub> according to the
 relationship established by Fleming and Gross (1990) and
 <i>L</i><sub>POH</sub> was used in all models (see
 below). Egg mass was used in all calculations, but only volume
 measurements were available for the Toboggan Creek population. Volume was
 transformed to weight by multiplying by the fraction of space occupied by
 random packed spheres (0.64; Finney 1970) and the average density of
 salmon eggs (1.076; Bonham 1976). A measure of reproductive investment,
 gonadal somatic index (<i>I</i><sub>G</sub>), was
 calculated from the average <i>M</i><sub>egg</sub>
 multiplied by average <i>F</i> and expressed as a ratio of
 gonad weight to somatic weight for each population and year that
 <i>M</i><sub>egg</sub>, <i>F</i>, and
 <i>L</i><sub>POH</sub> were available. To
 calculate female weight, <i>L</i><sub>POH</sub>
 was converted to fork length
 (<i>L</i><sub>F</sub>) by multiplying by 1.292 ·
 <i>L</i><sub>POH</sub> – 37.21 (Fleming and Gross
 1990). Based on a condition factor of 1.06 g · cm<sup>–3
 </sup>(<i>K</i>; 100 <i>M</i> ·
 <i>L</i><sub>F</sub><sup>–3</sup>),
 determined from Kitimat River population females,
 <i>L</i><sub>F</sub> was used to calculate an
 approximate total weight. A <i>K</i> of 1.06 for mature female
 Coho Salmon falls within the range reported by Scholz et al. (2011) for
 spawning female Coho Salmon. Environmental variables
 were chosen based on their expected importance for explaining variation in
 <i>L</i><sub>POH</sub>,
 <i>M</i><sub>egg</sub>, <i>F</i>, and
 <i>I</i><sub>G</sub> for anadromous salmon.
 Environmental data were collected from global positioning system
 measurements of spawning locations, the Terrain Resource Information
 Management maps and databases of hatchery operations from FOC. The average
 latitude (LAT) for each population was used with an accuracy of ± 3 m.
 Migration distance from the mouth of the Fraser River to the spawning
 grounds (<i>D</i><sub>MIG</sub>) was also
 calculated for each population. Years of hatchery operations
 (<i>YOH</i>) was based on the difference in time between when
 FOC initiated supplemental stocking for a population and when the data
 used for the analysis was collected. Stream width (<i>WD</i>)
 was categorized as either small (&lt; 5 m wetted width) or large
 (&gt; 5 m wetted width). Headwater (<i>HW</i>) sources
 were categorized as streams or lakes. For each
 location, temperature loggers (HOBO U-22; Onset Computer Corporation,
 Bourne MA) were placed in three different locations within the river
 mainstem or tributaries to the mainstem river (Tuor and Shrimpton 2019). A
 surface temperature logger and two to three intragravel temperature
 loggers were deployed at each site within a study reach; intragravel
 loggers within a site were a minimum of three meters apart to capture some
 of the potential variation in temperatures from different redds within
 each system. Intragravel temperature loggers were buried at a depth of
 approximately 25 cm. Loggers recorded temperature hourly for approximately
 six months throughout incubation from November 2012 to May 2013.
 Additional temperature data was provided by FOC for the Quinsam River
 (2000 to 2017) and Big Qualicum River (2005 to 2018) watersheds. Mean
 surface water temperature was calculated during the peak of spawning from
 November 16 to 30 (<i>T</i><sub>NOV</sub>).
 Average intragravel temperature
 (<i>T</i><sub>AVG</sub>) was calculated from
 November 16 to May 15 or until 750 ATU had been reached. Average
 intragravel temperature was calculated during the coldest period of
 incubation – the month of January
 (<i>T</i><sub>JAN</sub>). 
 References Fleming, I.A., & Gross,
 M.R. (1989). Evolution of adult female life history and morphology in
 Pacific salmon (coho: <i>Oncorhynchus kisutch</i>).
 <i>Evolution</i>, 43, 141–157. Meldrum, J.,
 Campbell, K., Van Will, P., Stiff, H.W., Nagtegaal, D., Miyagi, E.,
 & Duncan, K. (2017). Enumeration of juvenile and adult Coho salmon
 at Black Creek, Vancouver Island, 2013. <i>Canadian Manuscript
 Report of Fisheries and Aquatic Sciences</i>, 3116: viii + 273
 p. Tuor, K.M.F., & Shrimpton, J.M. (2019).
 Differences in water temperatures experienced by embryo and larval Coho
 Salmon (<i>Oncorhynchus kisutch</i>) across their geographic
 range in British Columbia. <i>Environmental Biology of
 Fishes,</i> 102, 955-967. DOI: 10.1007/s10641-019-00882-7