Are we ready to track climate-driven shifts in marine species across international boundaries? - A global survey of scientific bottom trawl data

Marine biota are redistributing at a rapid pace in response to climate change and shifting seascapes. While changes in fish populations and community structure threaten the sustainability of fisheries, our capacity to adapt by tracking and projecting marine species remains a challenge due to data discontinuities in biological observations, lack of data availability, and mismatch between data and real species distributions. To assess the extent of this challenge, we review the global status and accessibility of ongoing scientific bottom trawl surveys. In total, we gathered metadata for 283,925 samples from 95 surveys conducted regularly from 2001 to 2019. We identified that 59% of the metadata collected are not publicly available, highlighting that the availability of data is the most important challenge to assess species redistributions under global climate change. Given that the primary purpose of surveys is to provide independent data to inform stock assessment of commercially important populations, we further highlight that single surveys do not cover the full range of the main commercial demersal fish species. An average of 18 surveys is needed to cover at least 50% of species ranges, demonstrating the importance of combining multiple surveys to evaluate species range shifts. We assess the potential for combining surveys to track transboundary species redistributions and show that differences in sampling schemes and inconsistency in sampling can be overcome with spatio-temporal modeling to follow species density redistributions. In light of our global assessment, we establish a framework for improving the management and conservation of transboundary and migrating marine demersal species. We provide directions to improve data availability and encourage countries to share survey data, to assess species vulnerabilities, and to support management adaptation in a time of climate-driven ocean changes.En prensa6,86

Structure, characteristics and manegement of small-scale coastal fisheries in Greece

Small-scale fisheries are an important fisheries sector in Greece and the Mediterranean. They are characterized by high heterogeneity and a multitude of particularities. The management of small-scale fisheries requires taking into account biological as well as social and economical elements. In the present study, a typology of Greek small-scale fisheries was developed based on biological, social and economical parameters. Consequently, the study focused in the Patraikos Gulf, where elements such as the fishing activity of the local fleet, catch and catch per unit of effort, species composition, discards and length composition of individuals caught were examined. The prefectures of Greece were stratified considering the number of fishermen and local dependence on fisheries and interviews of fishermen were carried out. The multitude of fishing gears and target species and the intense spatial heterogeneity was confirmed. The major activity pattern identified was seasonal (20 days of activity in summer, 13 in winter), however local particularities arose. The main metiers practiced were identified as combinations of fishing gear, target species, area and season. Concerning socio-economical elements, the fishermen generally had low education, high average age, tendency to remain in their place of birth and the profession is attached to the family. The fishermen were categorized into three dependence groups, based on the percentage of income originating from fisheries. Significant differences were identified among these groups considering variables such as mean fishermen age, vessel size, days of activity and income from fishing. Consequently, the small-scale fisheries of the Patraikos Gulf were studied using data from sampling of fishing operations. The catch weighted about 12 kg per operation on average and a total of 102 species were recorded. A methodology for the identification of metiers using a limited dataset, as is often the case in the Mediterranean, was developed. The metiers identified showed significant differences in catch quantity and composition and were grouped in meta-metiers to facilitate fishing activity sampling schemes. The study of discards revealed three reasons for discarding: low commercial value (78% of discards), destruction of the catch before gear retrieval (5%) and bad handling of the catch on board (17%). High discard ratio was recorded for the longline and small-size mesh trammel net metiers. Using data of individual length per species, comparisons were carried out among metiers and seasons that in most cases revealed significant differences. The study of the effect of minimum landing sizes legislation showed a low percentage of undersized individuals regarding both the legislation currently in effect and the proposed one by the Roadmap for the Reform of the Common Fisheries Policy of the European Union, but exceptions arose for certain species. The present work is the foothold for the development of a methodology for studying small-scale fisheries in Greece and for carrying out comparative studies in a European scale concerning this understudied fishing sector.Η μικρή παράκτια αλιεία αποτελεί σημαντικό τμήμα του αλιευτικού κλάδου στnν Ελλάδα και τη Μεσόγειο και χαρακτηρίζεται από υψηλή ετερογένεια και πληθώρα ιδιαιτεροτήτων. Η διαχείριση της απαιτεί την εξέταση βιολογικών, αλλά και κοινωνικών και οικονομικών παραμέτρων. Στην παρούσα εργασία αναπτύχθηκε μία τυπολογία της ελληνικής μικρής παράκτιας αλιείας με βάση βιολογικά, κοινωνικά και οικονομικά χαρακτηριστικά. Στη συνέχεια η εργασία εστιάστηκε στον Πατραϊκό Κόλπο, όπου μελετήθηκε η δραστηριότητα της τοπικής μικρής παράκτιας αλιείας, η συνολική παραγωγή και η παραγωγή ανά μονάδα αλιευτικής προσπάθειας, η σύνθεση του αλιεύματος, τα απορριπτόμενα και η κατά μήκος σύνθεση των αλιευμάτων. Οι νομοί της Ελλάδας στρωματοποιήθηκαν βάσει του αριθμού των αλιέων και της εξάρτησης από την αλιεία και πραγματοποιήθηκαν συνεντεύξεις αλιέων. Επιβεβαιώθηκε η ποικιλία εργαλείων και ειδών-στόχων και η έντονη χωρική ετερογένεια. Το κυρίαρχο πρότυπο αλιευτικής δραστηριότητας εμφάνισε εποχικές διακυμάνσεις (20 ημέρες δραστηριότητας μηνιαίως το καλοκαίρι, 13 ημέρες το χειμώνα), παρουσίασε όμως τοπικές ιδιαιτερότητες. Οι κύριες ενασχολήσεις (metiers) που πραγματοποιούνται σε πανελλήνιο επίπεδο αναγνωρίστηκαν ως συνδυασμοί αλιευτικού εργαλείου, είδους-στόχου, εποχής και περιοχής με πολυμεταβλητή ανάλυση. Οι αλιείς παρουσίασαν χαμηλό μορφωτικό επίπεδο και υψηλή μέση ηλικία, υψηλά ποσοστά παραμονής στον τόπο γέννησης και διαπιστώθηκε έντονη παρουσία της οικογένειας στο επάγγελμα. Οι αλιείς χωρίστηκαν σε τρεις ομάδες εξάρτησης από την αλιεία βάσει του ποσοστού του εισοδήματος που προέρχεται από το ψάρεμα, οι οποίες εμφάνισαν διαφορές σε χαρακτηριστικά όπως η μέση ηλικία, το μήκος του σκάφους, οι ημέρες δραστηριότητας και το εισόδημα από το ψάρεμα. Στη συνέχεια μελετήθηκε η μικρή παράκτια αλιεία του Πατραϊκού Κόλπου με δειγματοληψίες σε αλιευτικές εξορμήσεις. Η αλιευτική παραγωγή ήταν κατά μέσο όρο 12 kg ανά αλιευτική εξόρμηση. Συνολικά, αναγνωρίστηκαν 102 είδη αλιευμάτων. Αναπτύχθηκε μία μεθοδολογία αναγνώρισης ενασχολήσεων σε περιπτώσεις περιορισμένου αριθμού δεδομένων, όπως συχνά συμβαίνει στη Μεσόγειο. Οι ενασχολήσεις που αναγνωρίστηκαν παρουσίασαν διαφορές στην ποσότητα και στη σύνθεση του αλιεύματος και ομαδοποιήθηκαν σε μετα-ενασχολήσεις με σκοπό την αποτελεσματικότερη δειγματοληψία της αλιευτικής δραστηριότητας. Η μελέτη των απορριπτομένων ανέδειξε τρεις αιτίες απόρριψης: χαμηλή εμπορικότητα (78% της απορριφθείσας ποσότητας), καταστροφή των αλιευμάτων κατά την παραμονή τους στο νερό (5%) και μείωση της ποιότητάς τους εξαιτίας κακών χειρισμών του ψαρά (17%). Υψηλό ποσοστό απόρριψης παρουσίασαν οι ενασχολήσεις παραγαδιών και μανωμένων διχτύων με μικρό άνοιγμα ματιού. Από τα δεδομένα ατομικού μήκους των αλιευμάτων πραγματοποιήθηκαν συγκρίσεις κατά μήκους σύνθεσης ανάμεσα σε διαφορετικές ενασχολήσεις και εποχές του έτους. Στις περισσότερες περιπτώσεις διαπιστώθηκαν διαφορές. Η μελέτη της επίπτωσης της εφαρμογής του ελάχιστου επιτρεπόμενου μεγέθους εκφόρτωσης έδειξε μικρό ποσοστό υπομεγεθών ατόμων στο αλίευμα βάσει τόσο των σημερινών σε ισχύ μεγεθών όσο και βάσει αυτών που πρόκειται να εφαρμοστούν σύμφωνα με τον Οδικό Χάρτη για την Αναθεώρηση της Κοινής Αλιευτικής Πολιτικής, σε επίπεδο είδους όμως παρουσιάστηκαν εξαιρέσεις. Η παρούσα εργασία αποτελεί τη βάση για την ανάπτυξη μεθοδολογίας για τη μελέτη της μικρής παράκτιας αλιείας στην Ελλάδα και την πραγματοποίηση συγκριτικών μελετών σε ευρωπαϊκή κλίμακα σε αυτόν τον λίγο μελετημένο αλιευτικό κλάδ

21 traits by 86 species in eastern Ionian fisheries

<p>This file contains traits data for 86 species appearing in the catches of the multi-species fisheries in the eastern Ionian Sea. There are data on 21 traits; for each trait, 2-6 trait categories/modalities exist and each species can only belong to one modality per trait.</p> <p>The excel file has 3 worksheets:</p> <p>(1) The first worksheet is a presence/absence (1/0) matrix of 86 species by 73 traits categories (or modalities).</p> <p>(2) The second worksheet is a matrix of the same 86 species by 21 traits with one or more numbers representing a reference.</p> <p>(3) The third worksheet is a list of reference numbers and the corresponding references.</p> <p> </p

Koutsidi_Moukas_Tzanatos_21_traits_by_235_species.xls

<p>This file contains traits data for 235 Mediterranean fisheries resource species. There are data on 21 traits; the data are presented in a continuous or a categorical form (in the latter case, for each trait 2-6 trait categories/modalities exist and each species can only belong to one modality per trait).</p> <p> </p> <p>The excel file has 5 worksheets:</p> <p> </p> <p>(1) <b>continuous_traits_235_species</b>: This worksheet contains information on the continuous traits (longevity, age-at-maturity, fecundity, maximum length, trophic level, depth, optimal temperature). For traits of the range type (e.g. depth) minimum and maximum values as well as the mean value are provided.</p> <p> </p> <p>(2) <b>complete_21_traits_205_species</b>: This worksheet is a presence/absence (1/0) matrix of 205 species by 75 traits categories (or modalities). Only the species with complete information (205 species) on all 21 traits are presented.</p> <p> </p> <p>(3) <b>incomplete_21_traits_235_species</b>: This worksheet is a presence/absence (1/0) matrix of 205 species by 75 traits categories (or modalities). All species, even with incomplete information (235 species) on all 21 traits are presented.</p> <p> </p> <p>(4) <b>reference_codes_per_trait</b>: This worksheet is a matrix of the 235 species by 21 traits with one or more numbers representing a reference from which the information to fill in the trait information (shown in the previous worksheets) was taken.</p> <p> </p> <p>(5) <b>reference_list</b>: This worksheet is a list of reference numbers and the corresponding full references.</p

Koutsidi_Moukas_Tzanatos_Table_S2.xls

<p>Koutsidi_Moukas_Tzanatos_Table_S2: The competition between 205 species of Mediterranean fisheries resources examined, specifically for (a) habitat use, (b) spawning habitat use, and (c) food resources of mature stages. </p><p>Species occurring in the same habitat (Posidonia beds, coralligene formations, lagoons) according to the cited sources are considered as competitors for the specific resource.</p><p> </p><p>The excel file has 3 worksheets:</p><p> </p><p>(1) habitat_use: This worksheet contains the 205 species examined, sorted by the modalities of the traits (depth, habitat type, seabed type) relevant to habitat use.</p><p> </p><p>(2) adult_food: This worksheet contains the 205 species examined, sorted by the modalities of the traits (maximum length, trophic level, feeding type) relevant to the use of food resources by mature fish.</p><p> </p><p> </p><p>(3) spawning_habitat: This worksheet contains the 205 species examined, sorted by the modalities of the traits (spawning period, spawning habitat) relevant to spawning habitat use.</p><p><br></p

Koutsidi_Moukas_Tzanatos_Table_S1.xls

<p></p><p>Koutsidi_Moukas_Tzanatos_Table_S1: Niche classification scheme for 205 species of Mediterranean fisheries resources, generated from a Regression tree analysis, using four niche descriptors (distribution, ecology, biology, behaviour). The file includes the traits of the nodes of each niche descriptor for each species examined.</p><br><p></p

Biology and fisheries of the spotted flounder (

Obtaining data to study fish biology can be a challenge if a stock is fished by a variety of gears with different effort units and different selectivity, particularly if these gears only partially overlap in space and time. In this work, we attempted to study the biology of the spotted flounder Citharus linguatula in the Patraikos Gulf and the adjacent central Ionian Sea (eastern Mediterranean) and to evaluate the current fisheries management. We characterized age composition and growth, length-at-maturity, and catch-per-unit-effort (CPUE) of spotted flounder from the catches of bottom trawls, gillnets and trammel nets for the period autumn 2013–2014. Variation of fish total length, gonadosomatic index, hepatosomatic index and condition factor was analyzed using generalized additive models (GAMs) with regard to sex, date, fishing gear and depth. We also modeled CPUE fluctuations of each gear by date, depth, longitude and latitude using GAMs. Fish age ranged from 1 to 5 years. A slightly allometric growth was documented with females attaining larger sizes than males. Length-at-maturity was 163 mm for females and 169 mm for males. The seasonal change of gonad maturity stages and the gonadosomatic index indicated spawning in late summer-autumn. Changes in length frequencies indicated that recruitment to the fisheries occurred in late spring-early winter in shallow depth (<40 m). The catch composition of trawls and the CPUE model results suggested that the selectivity of this gear should be regulated to reduce catching immature individuals of spotted flounder. The results further indicated that the seasonal trawl closure of the Patraikos Gulf contributes to reduce catching juveniles

Evidence of subtle genetic structure in the sympatric species Mullus barbatus and Mullus surmuletus (Linnaeus, 1758) in the Mediterranean Sea

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