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

Abstract Background Syngnathid fishes (Actinopterygii, Syngnathidae) are flagship species strongly associated with seaweed and seagrass habitats. Seahorses pipefishes highly vulnerable to anthropogenic environmental disturbances, but most currently Data Deficient according the IUCN (2019), requiring more biological ecological research. This study provides first insights into syngnathid populations in two marine Spanish National Parks (PNIA—Atlantic- PNAC—Mediterranean). Fishes were collected periodically, marked, morphologically identified, analysed for size, weight, sex sexual maturity, sampled stable isotope genetic identification. Due scarcity of previous information, habitat characteristics also assessed PNIA. Results diversity abundance low, identified PNIA ( Hippocampus guttulatus Syngnathus acus ) four PNAC S. abaster , typhle Nerophis maculatus ). Syngnathids from both (NP) differed isotopically, much lower δ 15 N than The dominant preferred less exposed sites macroalgal assemblages Cymodocea meadows PNAC. occurrence very large specimens, absence small-medium sizes isotopic comparison a nearby population suggest that (the PNIA) mainly comprised breeders migrate seasonally. Mitochondrial cytochrome b sequence variants detected H. acus, novel 16S rDNA haplotype was obtained N. . Our data presence cryptic divergent mitochondrial lineage Conclusions is multidisciplinary approach syngnathids NPs. Habitat preferences NPs differed. Further studies needed assess complex discarding potential misidentifications genus PNAC, evaluate migratory events We propose several preferential future monitoring some recommendations their conservation.