Effect of diet on breeders and inheritance in syngnathids: application of isotopic experimentally derived data to field studies

Abstract

Syngnathids are vulnerable ovoviviparous fishes in which males undergo repeated brooding within a reproductive season. The isotopic effects of diet on both breeders (pooled sexes) and parent-egg transmission have been demonstrated in a few fish species but never in syngnathids. Quantifying isotopic changes due to diet is necessary to assess parent-newborn conversions and to estimate accurate trophic enrichment factors (TEF). We assessed the isotopic (δ13C and δ15N) effects of 3 experimental diets on TEFs in seahorse Hippocampus guttulatus breeders and isotopic inheritance. Our results suggest that H. guttulatus follows an income-capital continuum pattern for parent-egg transmission. The isotopic variability in diets for breeders and the resulting experimentally derived TEFs were compared with fixed TEFs from reviews to estimate their impact on the relative contribution of potential prey sources in syngnathids from the Cíes archipelago (Atlantic Islands National Park, NW Spain). We estimated source contributions using stable isotope mixing models (SIMMs) by combining prey sources into ecologically informative groups and incorporating informative priors. We demonstrate that (1) most frequently used TEFs from reviews might not be suitable for all fish species, particularly syngnathids, and (2) dietary source variability has a great effect on source contribution estimates. This study is also the first to provide specific TEFs for syngnathids.

A multidisciplinary experimental study on the effects of breeders diet on newborn seahorses (Hippocampus guttulatus)

“…DHA, DHA/EPA) in late newborn batch releases suggests a more or less intense exhaustion of body resources, accompanied by decreases in survivals at 7 DAR and newborn size. This statement is also supported by the trends in newborn isotopic signatures (Planas et , 2020).…”

“…Hence, the identi cation of both diet quality and effective feeding periods (the time period needed to change the biochemical composition of eggs/fry) for optimum broodstock performance is of pivotal importance in enhancing newborn quality (Fernández-Palacios et al, 2011;Griffen, 2018). The present study and the pattern of isotopic changes discussed elsewhere (Planas et al, 2020) suggest that the reproduction type followed by H. guttulatus corresponds to a mixed capital-income strategy. This strategy usually implies a progressive drop in newborn quality in successive batches (McBride et al, 2016, Griffen, 2018.…”

“…However, the main dietary sources for H. guttulatus adults in our nearby region (NW Iberian Peninsula) are amphipoda (caprellids and gammarids), whereas mysidaceans are insigni cant prey in the bulk diet composition (Valladares et al, 2016). We recently demonstrated that diets including mysidaceans (alone or mixed with Artemia) provide the best trophic enrichment factors (laboratory derived) to infer the composition of bulk diet in wild syngnathids by means of isotopic signatures (Planas et al, 2020). Hence, even though mysidaceans might be considered a high quality prey for some seahorse species, it is very likely not suitable for breeding H. guttulatus when administered as the sole prey.…”

A multidisciplinary approach to identify priority areas for the conservation of a vulnerable family of fishes in Spanish Marine National Parks

“…Coastal sheltered areas protected from SW (TR1) and N waves (TR7-TR9) were preferred but areas with high bottom mobility (sand waves and megarriples 3D) were avoided (TR2 and TR4). Some syngnathid species appear to be generalist considering distribution patterns and algal community characteristics whereas others prefer certain seaweed forms and feed on speci c sources (Masonjones et al 2010;Planas et al 2020). Distribution patterns can be partially explained by the exposure to waves and open sea (Smith et al 2008;Masonjones et al 2010) which has a great impact on seaweed cover.…”

Effects of Tissue Preservation on Carbon and Nitrogen Stable Isotope Signatures in Syngnathid Fishes and Prey

“…Where lethal sampling is not desirable, other fish tissues such as fins and scales are non-lethal alternatives for muscle [13,[15][16][17][18], especially in threatened and endangered species [19][20][21][22]. The isotopic signals from those surrogate tissues can be converted to muscle values by means of mathematical corrections obtained from inter-tissue comparisons.…”