This study documents the presence of two uncommon tetraodontiform fishes and reviews the occurrence of species from this order in Spanish marine waters. Two tetraodontid specimens (Family Tetraodontidae) were caught in the Atlantic waters off the coast of Galicia, northwestern Spain. A specimen of Sphoeroides pachygaster was collected in 2021 off the Costa da Vela, while a specimen of Ephippion guttifer was captured in 2025 in the Ría de Pontevedra, both locations situated in southern Galicia. Morphological analyses, supported by photographic evidence and DNA barcoding, confirmed the preliminary taxonomic identification of the two species. Histological reproductive analysis of the Ephippion guttifer specimen revealed a female in the spawning-capable phase. These findings constitute the first verified record of S. pachygaster and the second of E. guttifer in Galician waters. An updated comprehensive list of tetraodontiform species found in Spanish waters across five geographical demarcations was compiled. Historically, a total of 26 species across five families have been reported in Spanish waters, with 22 in the Canary Islands and 15 in the Spanish Iberian Peninsula and Balearic Islands. Additionally, a review of the presence of neurotoxic tetrodotoxins (TTXs) or paralytic shellfish toxins (PSTs) in each species is included, providing an up-to-date overview of a largely unexplored field in European waters. The increasing occurrence of tetraodontiform fishes in Spanish waters provides further evidence of the progressive tropicalization of the Spanish marine environment.

Accurate fish stock evaluation requires proper identification of population structure, for which reproductive ecology studies are essential. This study examines blue whiting (Micromesistius poutassou), a widely distributed mesopelagic gadoid managed as a single stock in the Northeast Atlantic, despite ongoing debate about the existence of distinct spawning components. To investigate potential differentiation, we compared reproductive parameters between two regions: the Porcupine area in southwest Ireland (ICES division 27.7.c,k,h,j) and the Peninsula area off the northern Iberian Peninsula (ICES division 27.8.c-9.a.N). Using biological data from 2018 surveys of the Spanish Institute of Oceanography and commercial vessels, we analysed somatic attributes (length, weight and condition) and assessed the species’ reproductive strategy. We also examined interannual variation in Peninsular females’ somatic features, total and batch fecundity, and geographic variation in fecundity and spawning frequency in February–March. Blue whiting was confirmed as a capital breeder, spawning from February to April. Iberian individuals exhibited smaller sizes and lower condition but higher fecundity (mean potential and batch fecundity: 46.817 vs. 12.223 oocytes, 16.808 vs. 6.112 hydrated oocytes), releasing three batches per season at 11-day intervals, compared with one every ~15 days at Porcupine. These findings suggest a distinct southern component, reinforcing the relevance of reproductive studies for stock assessment and management.

This study reports on the presence of two uncommon tetraodontiform fishes and reviews the presence of species of this order in Spanish marine waters. Two tetraodontid specimens (Family Tetraodontidae) were caught in Atlantic waters of the coast of Galicia, northwestern Spain. A specimen of Sphoeroides pachygaster was collected in 2021 off the Costa da Vela, and a specimen of Ephippion guttifer was captured in 2025 within the Ría de Pontevedra, both locations situated in southern Galicia. Morphological analyses, supported by photographic evidence and DNA barcoding, confirmed the preliminary taxonomic identification of both species. The histological reproductive analysis of the Ephippion guttifer specimen showed a female in spawning capable phase. These findings constitute the first verified record of S. pachygaster and the second of E. guttifer in Galician waters. A comprehensive list of tetraodontiform species found in Spanish waters across five geographical demarcations has been compiled and updated. Historically, a total of 26 species across five families have been reported in Spanish waters, counting 22 in the Canary Islands and 15 in the Spanish Iberian Peninsula and Balearic Islands. Additionally, a review of the presence of the neurotoxic tetrodotoxins (TTXs) or paralytic shellfish toxins (PSTs) in each species is also included, bringing an up-to-date overview of a largely unexplored field in European waters. The increasing occurrence of tetraodontiform fishes in Spanish waters provides further evidence of the progressive tropicalization of the Spanish marine environment.