Historical trends and future distribution of anchovy spawning in the Bay of Biscay

Marine water environmental DNA metabarcoding provides a comprehensive fish diversity assessment and reveals spatial patterns in a large oceanic area

“…Compared to fish trawling, eDNA metabarcoding was able to “capture” a larger number of fish species. Both, eDNA and trawling based estimates (in number of reads and biomass, respectively) indicate that E. encrasicolus represents half of the abundance, which is consistent to the known large and stable anchovy population in the Bay of Biscay (Erauskin-Extramiana et al, 2019; Santos, Uriarte, Boyra, & Ibaibarriaga, 2018; Uriarte, Prouzet, & Villamor, 1996) and with the fact that the BIOMAN survey took place during the anchovy spawning season. The seven most abundant species in fish trawling representing >1% of the total biomass were T. trachurus, S. scombrus, T. mediterraneus, M. merluccius, M. poutassou, S. pilchardus and B. boops , which were all, except those not present in the reference database ( B. boops and T. mediterraneus ), also found in the eDNA metabarcoding data, and four of them ( E. encrasicolus, S. pilchardus , S. scombrus and M. poutassou ) were also among the most abundant species from eDNA data.…”

Earlier migration and distribution changes of albacore in the Northeast Atlantic

“…However, our study addresses the problem of biases that can affect catch information on migration, hence confirming earlier phenology within the warming period of 1981–2017. The phenological earliness is consistent with recent findings for other fish species in the area, such as the peak of anchovy spawning in the Bay of Biscay (5.5 days/dec; Erauskin‐Extramiana et al., ), and other marine species with similar rates of phenological advancement (4.4 days/dec; Poloczanska et al., ).…”

“…Because the distribution and phenology of albacore juveniles is partially determined by oceanographic conditions (83%–93% accuracy), future projections of climate change might affect these variables. The regional future projections for the Bay of Biscay for an ensemble of 16 IPCC‐AR5 () climate models (Cabré, Marinov, & Leung, ) under RCP8.5 climate change scenarios by the end of the 21st century (2080–2099), compared to present (1980–1999), indicate sea surface warming (2.3°C), sea thermal stratification (−36 m in mixed layer depth), and decreases in surface salinity (−0.6; Erauskin‐Extramiana et al., ). Future sea warming is also expected in the tropical and subtropical North Atlantic (Cabré et al., ), where juveniles and pre‐adults start their feeding migration to the Bay of Biscay and southeastern Ireland in late spring.…”

Modelling species presence–absence in the ecological niche theory framework using shape-constrained generalized additive models

“…The second case study involves the incorporation of several variables in order to find species probabilities of occurrence combining different types of variables. Results are similar to those reported in other studies that needed manual selection of smoother parameters such as the probability of presence of anchovy eggs along salinity or sea surface temperature reported in Erauskin-Extramiana et al (2019) or the estimated optima for mackerel spawning along the salinity gradient in Brunel et al (2018). It is shown that the framework of SC-GAMs enables us to fit both unconstrained and shape-constrained shapes for each of the included variables depending on the type and prior knowledge.…”