Does sand content in spawning substrate result in early larval emergence? Evidence from a lithophilic cyprinid fish

Abstract

The spawning success of lithophilic salmonids is strongly influenced by the fine sediment content ('fines') of spawning substrates, yet knowledge on the impacts of fines on the spawning of non-salmonid lithophiles remains limited, despite their ecological and socioeconomic importance in European rivers. Consequently, the aim here was to use an ex-situ experiment to investigate the impact of sand content on egg survival and timing of larval emergence of the surface-spawning cyprinid European barbel Barbus barbus. Thirty incubator boxes within a recirculating system were filled with one of five experimental sediment mixtures (0 to 40 % sand by mass) that each contained 300 fertilised eggs at a depth of 50 mm. Emerged, free-swimming larvae were captured and counted daily to assess grain size effects on larval survival and emergence. Specifically, total proportion of emerged larvae, cumulative daily proportion of emerged larvae and time required to reach 50 % emergence were measured during the study. Whilst the proportion of sand in the sediments did not have a significant impact on egg-to-emergence survival (mean survival per treatment 75 % to 79 %), it significantly affected the timing of larval emergence to the water column; early emergence was detected in treatments with elevated sand content (on average, 50 % emergence after 12-13 days versus 19 days in the control). Similar to findings from salmonid studies, these results suggest high sand content in spawning gravels can influence timing of larval emergence and potentially cyprinid lithophilic fish survival. 3 1 INTRODUCTION Availability and suitability of spawning habitats are important determinants of fish population viability in freshwater ecosystems (

Substrate composition determines emergence success and development of European nase larvae (Chondrostoma nasus L.)

“…The timing of emergence in the substratum mixtures was significantly affected by the substrate composition, creating a higher variation in the timing of emergence, for example an increasing time span of emergence, by an increasing content of fines. Effects of sand in the spawning substrate have also been reported for barbel, where hatched larvae showed early emergence in treatments with elevated sand content (Bašić, Britton, Rice, & Pledger, 2018). Additionally, high fine sediment shares in spawning substrate might form a physical barrier that slow down the emergence process, which is evident by the high numbers of physically blocked larvae in treatment F (20% fines).…”

“…Effects of sand in the spawning substrate have also been reported for barbel, where hatched larvae showed early emergence in treatments with elevated sand content (Bašić, Britton, Rice, & Pledger, 2018). Effects of sand in the spawning substrate have also been reported for barbel, where hatched larvae showed early emergence in treatments with elevated sand content (Bašić, Britton, Rice, & Pledger, 2018).…”

Quantifying the habitat and zoogeomorphic capabilities of spawning European barbelBarbus barbus, a lithophilous cyprinid

“…The barbel egg survival estimates from the parameterised salmonid models should be used cautiously, given the divergence in the egg survival rates from the salmonid model and the ex‐situ egg survival rates of Bašić et al (). Reasons for this are likely to include the higher oxygen requirements of salmonid eggs, although there is a paucity of information on the oxygen requirements of cyprinid eggs (Elshout, Dionisio Pires, Leuven, Wendelaar Bonga, & Hendriks, ).…”

“…Thus, their eggs are exposed to fines for longer periods than the eggs of fast‐incubating spring/summer spawning cyprinids (Bašić et al, ). Exception to this longer period of exposure to fines in salmonids includes spring‐spawning steelhead trout Oncorhynchus mykiss with a 7 to 10 day incubation period (Goode et al, ; Phillips, Lantz, Claire, & Moring, ) versus 12 to 20 days in barbel (Bašić, Britton, Rice, & Pledger, ) under similar sediment but different temperature conditions (steelhead: 7–11°C, barbel: 16–18°C). Another key difference is the egg diameter, with salmonid eggs generally larger than cyprinid eggs (5–9 mm vs. 0.5–3.0 mm, respectively) (salmon: Aulstad & Gjedrem, ; Beacham & Murray, ; barbel: Pinder, ), indicating higher metabolic demand for salmonid eggs (Rombough, ).…”

“…Salmonid eggs are also often buried deeper (salmonids: 11–30 cm depth; cyprinids 3–17 cm depth; Table ), with oxygen availability decreasing as sediment depth increases (Freixa et al, ). Because of these differences, the effects of fine sediment on spawning success of barbel remains unclear and although Bašić et al () revealed delayed larval emergence from substratum with high sand content (>30% sand by mass), impacts on egg‐to‐emergence survival were not detected.…”