This study generated bioactive hydrolysates using the enzyme Alcalase and autolysis from mesopelagic fish, including Maurolicus muelleri and Benthosema glaciale. Generated hydrolysates were investigated for their bioactivities using in vitro bioassays, and bioactive peptides were identified using mass spectrometry in active hydrolysates with cyclooxygenase, dipeptidyl peptidase IV and antioxidant activities. In silico analysis was employed to rank identified peptide sequences in terms of overall bioactivity using programmes including Peptide Ranker, PrepAIP, Umami-MRNN and AntiDMPpred. Seven peptides predicted to have anti-inflammatory, anti-type 2 diabetes or Umami potential using in silico strategies were chemically synthesised, and their anti-inflammatory activities were confirmed using in vitro bioassays with COX-1 and COX-2 enzymes. The peptide QCPLHRPWAL inhibited COX-1 and COX-2 by 82.90% (+/−0.54) and 53.84%, respectively, and had a selectivity index greater than 10. This peptide warrants further research as a novel anti-inflammatory/pain relief peptide. Other peptides with DPP-IV inhibitory and Umami flavours were identified. These offer potential for use as functional foods or topical agents to prevent pain and inflammation.

Bioactive peptides are sequences of amino acids, cut from the parent protein with en-zymes or high pressure processing that can impart a tertiary health benefit to the con-sumer that goes beyond basic human nutrition. This study explores mesopelagic fish in-cluding Maurolicus muelleri and Benthosema glaciale as sources of peptides with an-ti-inflammatory, heart health beneficial, antioxidant and other bioactivities. Bioactive peptides were generated post-catch using different enzymatic hydrolysis processes ap-plied to mesopelagic species caught from experimental cruises targeting these fish. Maurolicus muelleri and Benthosema glaciale were the dominant species processed. Bi-oactive hydrolysates included a Maurolicus muelleri Alcalase hydrolysate and a Maurolicus muelleri autolysis. Hundreds of peptide sequences were identified using mass spectrome-try from active hydrolysates. In silico analysis was used to rank identified peptide se-quences in terms of overall bioactivity using Peptide Ranker, anti-inflammatory activity using PrepAIP, ability to impart Umami flavours with Umami-MRNN and dipeptidyl peptidase IV inhibitory potential using AntiDMPpred . Thirty peptides were selected fol-lowing in silico analysis. Several of the selected peptides had sequence homology with peptides derived from other fish proteins including Atlantic salmon (peptide QCPLHR-PWAL) and thin-lipped mullet (peptide FDAFLPM). Seven peptides predicted to have an-ti-inflammatory, anti-type 2 diabetes or Umami potential using in silico strategies were chemically synthesized and their anti-inflammatory activities confirmed using in vitro bioassays with COX-1 and COX-2 enzymes. The peptide QCPLHRPWAL inhibited COX-1 and COX-2 by 82.90% (+/-0.54) and 53.84% respectively and had a selectivity index greater than 10. This peptide warrant further research as a novel anti-inflammatory/pain relief peptide. Other bioactivities associated with DPP-IV inhibition and Umami flavours de-velopment are discussed. Identified peptides offer potential for use in functional foods or topical agents to prevent pain and inflammation associated with diseases like psoriasis, arthritis and inflammatory bowel disease, however further research in vivo is required.

Interest in mesopelagic fish layers is on the rise due to the potential exploitability of their macrofauna; hence, profiling their fish community is crucial to enable the sustainability of future fishing practices. In this context, a dedicated survey was carried out in September 2022 along the Irish shelf break, where fishing (catch) and eDNA metabarcoding analysis using a portable high-throughput sequencer were performed to investigate the fish community of the upper mesopelagic layer. Catch data showed that the targeted layers consisted mainly of the young-of-the-year cohort of Mueller’s pearlside (Maurolicus muelleri), a mesopelagic fish, with little bycatch. eDNA data reflected the high prevalence of M. muelleri’s eDNA (56%–97% of assigned reads), identified species undetected by fishing, and showed that the least represented species differed in water samples collected before or after fishing activities. While this reflects current limitations of each technique, it also shows that a multidisciplinary approach may provide an increased level of resolution for M. muelleri layer’s ancillary fish community. Findings from the present study provided important insights to further refine sample acquisition and rapid processing of eDNA metabarcoding data, which beholds great potential to corroborate fishing methods when ground truthing acoustic approaches in mesopelagic fish layers assessments.

Estuaries are crucial ecosystems where human activities deeply affect numerous ecological functions. Here we present a survey dataset based on the monitoring of fish nursery grounds of the Seine estuary and eastern bay of Seine collected once a year using a beam trawl during three distinct periods (1995-2002, 2008–2010 and 2017–2019). The surveys happen at the start of autumn in order to maximize the catchability of juvenile fish. The beam trawl mainly targets benthic and demersal species on a study area that extends over 600 square kilometers. The dataset includes abundance and densities of 161 species for 634 hauls performed around 40 stations each year. These data can be used by fishery scientists and ecologists motivated by early life stages of commercial species or by the impact of human disturbances, such as harbor developments, on estuarine communities.

Maurolicus muelleri is an important component of mesopelagic ecosystems; nevertheless, we possess only limited knowledge about its biological features. We collected samples of M. muelleri from six scientific surveys between 2019 and 2021 in three geographical areas in the Northeast Atlantic waters (from South to North): the Bay of Biscay, the Celtic Sea, and the Norwegian Sea. Geographical variations in otolith growth, fish age, length, weight, and condition, as well as length–weight relationships and von Bertalanffy growth models (VBGMs), were investigated. Length-weight relationships revealed differences associated with the fish’s origin, paralleling the annual and daily otolith growth. VBGM parameters increased progressively northwards, in accordance with Bergmann’s rules. Fish length was positively related to the otolith radio, and Lee’s phenomenon was undetected. The impact of environmental variables, such as temperature and food availability, is debated, with these considered potential drivers of this variability. Populations may belong to separated units, either genetically or morphologically, representing differences in biological parameters as a signal of geographical divergence.