Male sexual signaling and expected effects of hatchery-induced sperm competition vary with water depth at which whitefish are caught

Salmonids like whitefish (Coregonus spp.) are often propagated in supportive breeding. Spawners are caught from their spawning locations, their gametes mixed, and the resulting offspring reared in a protected environment before being released into the wild. This procedure can affect sexual selection, for example, by enhancing the importance of sperm competition or by reducing the relevance of sexual signals. While it is often unclear how sperm competitiveness is affected by a male’s overall genetic quality, there is accumulating evidence that sexual signals reveal good genes and that mate choice based on such signals can increase offspring viability (Auld et al. 2019). Therefore, supportive breeding may affect the genetic variance and the mean genetic quality of next generations. We sampled whitefish from various locations along a depth gradient to test how male characteristics that are likely to affect sexual selection under natural conditions correlate with characteristics that af..., Adult whitefish (Coregonus suidteri, n=104) were caught from Lake Hallwil (Switzerland; 47.2772° N, 8.2173° E) during their breeding season in January 2020 using gill nets set at 40, 25, 12, or 4 m depth along a line perpendicular to the bank (at decreasing distance to the shore, following the natural depth gradient). The nets were separated by distances of about 230, 50, and 40 m, respectively. At each depth, gill nets of 25, 27, 30, and 35 mm mesh size were used to ensure that adult whitefish of all size could be caught. Fish were immediately killed and kept in ice water until further processing. Standard body length (i.e. excluding the caudal fin) was determined, and scales were sampled above the lateral line from the caudal half of the body to later estimate fish age based on the number of annuli, a method offering same age estimates as methods based on otoliths or fin ray for fish younger than 5 years (Muir et al. 2008). Milt was collected by applying gentle bilateral abdominal pre...,

诸如白鲑（Coregonus spp.）的鲑科鱼类常被实施辅助繁育（supportive breeding）。具体操作流程为：从产卵场捕获产卵亲体，混合其配子，将获得的后代在人工保护环境中培育后再放归野外。该繁育程序可能会对性选择造成影响，例如加剧精子竞争的重要性，或是降低性信号的相关性。尽管目前尚不清楚雄性整体遗传质量如何影响精子竞争力，但越来越多的证据表明，性信号能够体现优良基因，基于此类信号的配偶选择可提升后代存活力（Auld等，2019）。因此，辅助繁育可能会改变子代的遗传方差与平均遗传质量。

本研究沿深度梯度选取多个位点采集白鲑样本，以检验自然条件下可能影响性选择的雄性特征，与……（原文此处截断）之间的相关性。

2020年1月繁殖季，于瑞士哈尔维尔湖（Lake Hallwil；北纬47.2772°，东经8.2173°）使用刺网捕获成年白鲑（Coregonus suidteri，样本量n=104）。刺网沿垂直于湖岸的方向布设，对应离岸距离递减的自然深度梯度，布设水深分别为40、25、12与4米，各层刺网之间的间距依次约为230、50与40米。针对每个水深梯度，分别使用网目尺寸为25、27、30及35毫米的刺网，以确保可捕获不同体型的成年白鲑。捕获后的鱼类立即处死，置于冰水中保存以待后续处理。测量其标准体长（不含尾鳍），并从身体后半段的侧线上方采集鳞片，后续将通过鳞片上的年轮数量估算鱼龄——该方法对于5龄以下鱼类的年龄估算结果，与基于耳石（otoliths）或鳍条（fin ray）的方法等效（Muir等，2008）。通过轻柔的双侧腹部按压采集精液（milt）……