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Cartilaginous Fishes: Stock Assessment and Population Dynamics

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A special issue of Fishes (ISSN 2410-3888). This special issue belongs to the section "Biology and Ecology".

Deadline for manuscript submissions: closed (31 October 2022) | Viewed by 20911

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Special Issue Editors

Dr. Fabrizio Serena

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Guest Editor

Institute for Marine Biological Resources and Biotechnology of the National Research Council (CNR-IRBIM), Via Vaccara, 61-91026 Mazara del Vallo, TP, Italy
Interests: chondrichthyans; fisheries science; stock assessment; taxonomy; marine ecology; biodiversity; conservation biology; scientific diving
Special Issues, Collections and Topics in MDPI journals

Dr. Fabio Fiorentino

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Guest Editor

Institute for Marine Biological Resources and Biotechnology (IRBIM), National Research Council (CNR), Mazara del Vallo, Italy
Interests: fish biology; fishery ecology; stock assessment; fishery management
Special Issues, Collections and Topics in MDPI journals

Dr. Alvaro Juan Abella

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Guest Editor

Private Consultant in fisheries science. Via Rana Ca’Mori 20 Este 35042, Italy
Interests: Fisheries; Fisheries Science; Stock Assessment; Fisheries Management; Fisheries Sustainability; Marine Ecology

Special Issue Information

Dear Colleagues,

We are preparing a Special Issue on the stock assessment and population dynamics of cartilaginous fishes considered at a global level.

One of the main problems for the scientific and sociopolitical community is the sustainability of fishery. The ongoing overexploitation of stocks determines not only the impoverishment of fish populations but also the loss of biological diversity. This situation is the main concern for managers and researchers engaged in the search for clear and sustainable solutions to reverse the negative evolution of fisheries.

The numerous management approaches adopted worldwide are evidence of the large variety of basic assumptions connected to the human–nature relationship. These assumptions are often complex and turn out to be ever closely linked to human habits and interests. The aim of our initiative is to contribute to the open discussion on how to improve stock assessment and management advice by taking into account both the ecological and socioeconomic dimensions of fisheries.

Elasmobranchs are a good example of the importance of this discussion, as they play a primary role in ecosystem balance. Being top predators in the food web, their eventual decrease in terms of biomass or number of individuals, or even their disappearance, threatens to alter the ecological equilibrium of marine communities through trophic cascades, with some consequences also being irreversible.

Our intention is to present a review of the current views in addition to more suitable assessment methods for the management and conservation of stocks, taking into account that elasmobranchs are often a bycatch in fisheries that target other species. Aside from knowledge of the population size and list of species present in each area, it is necessary to define their exploitation status and the negative effects that afflict their populations, which occur mostly as a result of excessive and indiscriminate fishing activities and habitat degradation. Therefore, when we consider the role that elasmobranchs have in the marine ecosystem, we should be discussing an integrated approach that employs multiple practices to address exploitation, conservation, and other relevant issues.

The global assessment framework aims to reduce bycatch and the threats to biodiversity in order to ensure sustainable use. The monitoring and assessment of fishery resources is therefore of vital importance for the maintenance of fish stocks, primarily of all top predators, such as elasmobranchs.

Dr. Fabrizio Serena
Dr. Fabio Fiorentino
Dr. Alvaro Juan Abella
Guest Editors

Short Biography

Dr. Fabrizio Serena

Fabrizio Serena graduates in Biological Sciences at the University of Pisa-Italy.
Since 1975 takes part in several research programmes of the Italian Ministry. He is involved in studies of stock assessment and management, population dynamics, ichthyological taxonomy.
Between 1985-2017, he was scientist in the GRUND national project and from 1994 in the EU international project MEDITS, both aimed at the assessment of demersal resources.
He is scientific advisor for the Food and Agriculture Organization of the United Nations, and for the UNEP-MAP, associate senior research at the CNR-IRBIM and IUCN Co-Regional Vice-Chair for Shark Specialist Group of the Mediterranean and Black Sea. For the EU he attended the European Commission - Directorate-General Fisheries - Conservation policy Management of Elasmobranchs stocks.
Has authored 3 books, 4 field guides and over 260 publications.

Dr. Fabio Fiorentino

Fabio Fiorentino, PhD in marine environmental science, senior researcher of Institute for Marine Biological Resources and Biotechnologies (IRBIM) of Italian National Research Council (CNR) at Mazara del Vallo (Italy).
Responsible of research projects on fishery data collection, stock assessment and management of fishery resources in the Mediterranean.
Member of national and international working groups dealing with sustainable fishing strategies.
Coordinator of the Sub Committee on Stock Assessment of the Scientific Advisory Committee (SAC) of the General Fisheries Commission of the Mediterranean (GFCM) from 2010 to 2013.
Italian National Focal Point for the FAO Regional Project MedSudMed.
Author of 80 scientific papers in ISI journals and numerous articles and technical reports on Mediterranean fisheries.

Dr. Alvaro Juan Abella

University degree in Biological Sciences, specialized in Zoology of Vertebrates, Montevideo University (Uruguay).
1972-1975. In the Zoology Department of the University of the Republic in Uruguay working in sharks taxonomy and biology.
1975-1980 Work in the National Fisheries Institute of Uruguay on stock assessment and biology of demersal fishes.
1980-1985 work on stock assessment in the National Research Council in Mazara del Vallo, Italy
1985 1989 Work as FAO senior expert carrying out studies and field surveys on board research vessels along the coasts of Western Africa, Caribbean Sea and Eastern Pacific.
1989-2016 Senior scientist in the Agency for the Protection of the Environment in Livorno, working on assessment of renewable marine resources, in Italy
Since 1995 he works as independent expert involved in many international projects.
He has published more than 100 scientific papers on taxonomy, population dynamics and biology of sharks and bony fishes, many of them published in peer reviewed international journals.
He has been lecturer in many training courses on stock assessment held in Egypt, Libya, Turkey, Bulgaria and Italy.
Since 2008 he is a permanent member of the Scientific, Technical and Economic Commission of Fisheries of the European Commission.

Manuscript Submission Information

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Keywords

stock assessment
management
bycatch

Published Papers (8 papers)

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Research

22 pages, 6612 KiB

Open AccessArticle

Conservation Status Assessment of Demersal Elasmobranchs in the Balearic Islands (Western Mediterranean) over the Last Two Decades

by Alba Serrat, Maria Teresa Farriols, Sergio Ramírez-Amaro, Francesc Ordines, Beatriz Guijarro, Francesca Ferragut-Perello and Enric Massutí

Fishes 2023, 8(5), 230; https://doi.org/10.3390/fishes8050230 - 27 Apr 2023

Cited by 2 | Viewed by 1761

Abstract

More than half of the Mediterranean sharks and rays are threatened by fishing exploitation. However, population assessments are limited by the scarcity of specific data on fishing catches. In this study, we assessed temporal trends of the indicators developed within the European Marine Strategy Framework Directive over the last two decades in order to assess the conservation status of demersal sharks and batoids in the Balearic Islands, which represent an important fraction of the bycatch of bottom trawling in this area. On the basis of a georeferenced, fishery-independent dataset of 19 species of elasmobranchs, we analyzed 20 year time series (2002–2021) of nine indicators regarding area distribution, population size, population status, and community structure. Between 30% and 50% of the elasmobranch species and functional groups showed increasing trends in distribution area and population size. This was especially true for batoids, whereas the distribution area and population size of most sharks remained stable over the study period. The remaining indicators showed stability or, in some cases, variable trends. Only in one case did we find a negative trend sustained all along the time series (i.e., the proportion of R. radula large individuals in relation to the reference period). Overall, our results suggest that the populations of elasmobranchs from the Balearic Islands show stable or recovery trends, mainly in terms of distribution area and density. However, it remains elusive whether this community can recover to the levels of more than half a century ago, before the development of the bottom trawl fishery, or whether this apparent current steady state should be interpreted as a new equilibrium. Full article

(This article belongs to the Special Issue Cartilaginous Fishes: Stock Assessment and Population Dynamics)

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14 pages, 2464 KiB

Open AccessArticle

Exploitation and Conservation Status of the Thornback Ray (Raja clavata) in the Balearic Islands (Western Mediterranean)

by Francesca Ferragut-Perello, Sergio Ramírez-Amaro, Athanassios C. Tsikliras, Natalia Petit-Marty, Donna Dimarchopoulou, Enric Massutí, Alba Serrat and Francesc Ordines

Fishes 2023, 8(2), 117; https://doi.org/10.3390/fishes8020117 - 19 Feb 2023

Cited by 1 | Viewed by 2177

Abstract

Fisheries management requires the best scientific knowledge on the exploitation and conservation status of stocks. This is challenging for by-catch species, for which necessary data for their assessment is more limited than for target ones. That is the case for the thornback ray, Raja clavata, in the Balearic Islands (western Mediterranean), whose exploitation and conservation status are addressed here for the first time, in an integrative approach, by using innovative assessment methods and genetic diversity analysis. The time series of fishing landings from 1964 and MEDITS trawl survey data from 2004 were used to apply CMSY++ and Bayesian state-space Schaefer production models. We also estimated the genetic diversity of the Cytochrome C Oxidase subunit I mitochondrial gene from 31 individuals collected during MEDITS surveys. The species showed overexploitation with a current fishing mortality (F) below that producing maximum sustainable yield (F_MSY), but with a current stock biomass (B) lower than B_MSY. Despite the fact that the exploitation status is stable or even has improved in the last decades, the overexploitation period since the late 1970s seems to have reduced levels of genetic diversity, below those of related species and other populations of R. clavata. This low genetic diversity may entail the loss of adaptive potential, making the species more vulnerable to fishing and the current climate change. Full article

(This article belongs to the Special Issue Cartilaginous Fishes: Stock Assessment and Population Dynamics)

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11 pages, 1352 KiB

Open AccessArticle

Opportunistic Survey Analyses Reveal a Recent Decline of Skate (Rajiformes) Biomass in Falkland Islands Waters

by Andreas Winter and Alexander Arkhipkin

Fishes 2023, 8(1), 24; https://doi.org/10.3390/fishes8010024 - 30 Dec 2022

Cited by 2 | Viewed by 1574

Abstract

Data were combined from surveys in 2013, 2018, 2019 and 2021 to examine biomass changes of the skate (Rajiformes) stock in waters around the Falkland Islands. The 2013 and 2019 surveys were research surveys for skate abundance and used 90 mm trawl mesh to capture species and size compositions. The 2018 survey was a mesh size trial, and the 2021 survey was a commercial exploration; both used 400 mm trawl mesh to target skates. All four surveys were compared for biomass by deselecting the proportions of skates per size interval caught in 90 mm mesh that would not have been caught in 400 mm mesh, calculated with the SELECT method. Estimated commercial-size skate biomass decreased for most species individually and approximately 61% overall. Estimated commercial-size skate biomass also decreased by as much south of 51° latitude, the area that was closed to skate target fishing since 1996, as north of 51° latitude, which has been maintained open to skate target fishing. The outcome is correlated with continuing skate bycatch in finfish trawls. Full article

(This article belongs to the Special Issue Cartilaginous Fishes: Stock Assessment and Population Dynamics)

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20 pages, 871 KiB

Open AccessArticle

An Annotated Checklist and the Conservation Status of Chondrichthyans in the Adriatic

by Alen Soldo and Lovrenc Lipej

Fishes 2022, 7(5), 245; https://doi.org/10.3390/fishes7050245 - 19 Sep 2022

Cited by 10 | Viewed by 2690

Abstract

Although there is a high number of publications listing fish species in the Adriatic, only a few have focused on chondrichthyans, while their conservation status has been investigated even less. Thus, this paper aims to provide an updated and annotated checklist of the chondrichthyans occurring in the Adriatic waters with their presence and conservation status. Each species is evaluated against the criteria defined in IUCN (International Union for Conservation of Nature) Red List Categories and Criteria and according to the guidelines for national and regional level assessments. In total, 60 chondrichthyan species from 27 families and 42 genera are listed. The list contains 33 species of sharks, 26 species of rays and one chimera. Assessment of the conservation status reveals that three species are now considered Regionally Extinct (namely Squatina oculata, Pristis pectinata and Rhinobatos rhinobatos). A total of 21 species are assessed as Critically Endangered, 8 are Endangered and 10 are Vulnerable. Of the remaining species, six are Near Threatened and the same number of species are Least Concern and Data Deficient. Considering that the principal driver of chondrichthyan decline and regional extinction is overfishing, it is recommended that the Adriatic countries adopt the same management measures and strengthen their coordination. Full article

(This article belongs to the Special Issue Cartilaginous Fishes: Stock Assessment and Population Dynamics)

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12 pages, 1576 KiB

Open AccessEditor’s ChoiceArticle

An Updated Greek National Checklist of Chondrichthyans

by Ioannis Giovos, Roxani Naasan Aga-Spyridopoulou, Fabrizio Serena, Alen Soldo, Adi Barash, Nikolaos Doumpas, Georgios A. Gkafas, Dimitra Katsada, George Katselis, Periklis Kleitou, Vasileios Minasidis, Yannis P. Papastamatiou, Eleana Touloupaki and Dimitrios K. Moutopoulos

Fishes 2022, 7(4), 199; https://doi.org/10.3390/fishes7040199 - 09 Aug 2022

Cited by 4 | Viewed by 3192

Abstract

Accurate checklists of species are essential for evaluating their conservation status and for understanding more about their distribution, biology and ecology and, therefore, the first step in order to effectively protect them. According to the existing literature, the Greek seas are rich in chondrichthyan biodiversity and herein, we update the most recent chondrichthyan checklist for the country regarding the species that are present in the Greek waters, correct unvalidated miscellaneous sightings and observations and provide guidelines about future research to improve their conservation. In total, 330 sources were collected from which 276 were used for further analysis, resulting in 1485 records of 67 species, among which 61 are confirmed by experts, including 34 sharks, 26 batoids and one chimaera. We are further listing six species as “Questionable/Not Confirmed”. Full article

(This article belongs to the Special Issue Cartilaginous Fishes: Stock Assessment and Population Dynamics)

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15 pages, 1435 KiB

Open AccessEditor’s ChoiceArticle

Length-Based Assessment Methods for the Conservation of a Pelagic Shark, Carcharhinus falciformis from the Tropical Pacific Ocean

by Richard Kindong, Ousmane Sarr, Feng Wu and Siquan Tian

Fishes 2022, 7(4), 184; https://doi.org/10.3390/fishes7040184 - 25 Jul 2022

Cited by 11 | Viewed by 3271

Abstract

The silky shark, Carcharhinus falciformis is one of the most heavily exploited sharks, being the main by-catch species in both tuna longline and purse-seine fisheries in tropical waters worldwide. Despite this severe exploitation, little is known about the species’ life history and population status. Silky sharks, like many other sharks, exhibit slow growth and low fecundity, indicating the urgency of developing assessment studies to aid in the implementation of conservation plans for their stocks. Because information on the catch and effort of this species is scarce, some length-based data-limited methods were applied in the present study to provide estimates of the status of the tropical Pacific silky shark population. As evident from the LBSPR analysis, the current spawning potential ratio (SPR) was found to be below the target reference point of SPR 40% and slightly above the limit reference point of SPR 20%. In addition, the LBB model also confirmed that this stock’s status is overfished with relatively low biomass levels. Furthermore, both models showed estimates of size selectivity at 50% and 95% that were lower than the estimated size at sexual maturity. In conclusion, the data-limited models developed in this study indicated that the silky shark stock in the tropical Pacific Ocean may be at risk of further decline. Additionally, the results show that growth and recruitment overfishing may be occurring in the silky shark’s population calling for immediate intensification of monitoring programs for these sharks as a pre-requisite to develop efficient management and conservation plans in the Pacific Ocean. Full article

(This article belongs to the Special Issue Cartilaginous Fishes: Stock Assessment and Population Dynamics)

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10 pages, 2287 KiB

Open AccessCommunication

Diel Vertical Habitat Use Observations of a Scalloped Hammerhead and a Bigeye Thresher in the Northern Gulf of Mexico

by Taylor Anderson, Emily N. Meese, James Marcus Drymon, Gregory W. Stunz, Brett Falterman, Elias Menjivar and R. J. David Wells

Fishes 2022, 7(4), 148; https://doi.org/10.3390/fishes7040148 - 24 Jun 2022

Viewed by 2412

Abstract

Understanding habitat use of elasmobranchs in pelagic environments is complicated due to the mobility of these large animals and their ability to move great distances in a three-dimensional environment. The Gulf of Mexico is a region where many highly migratory pelagic shark species occur, while in close proximity to coastal, anthropogenic activity including recreational and commercial fisheries. This study provides summary information on the vertical habitat use for a single male scalloped hammerhead and a single male bigeye thresher that were each caught and tagged with an archiving satellite tag. The scalloped hammerhead occupied shallow depths (<100 m) over the continental shelf during the 90 d deployment. The bigeye thresher exhibited strong patterns of diel vertical migrations by occupying depths below the thermocline (>350 m) during the day, then occupying shallower depths (50–100 m) during the night. By providing summary information, this note urges future research to provide scientific information on pelagic, highly migratory species for management efforts in the Gulf of Mexico region. Full article

(This article belongs to the Special Issue Cartilaginous Fishes: Stock Assessment and Population Dynamics)

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16 pages, 4737 KiB

Open AccessFeature PaperArticle

Assessing the Stock Dynamics of Elasmobranchii off the Southern Coast of Sicily by Using Trawl Survey Data

by Fabio Falsone, Vita Gancitano, Michele Luca Geraci, Giacomo Sardo, Danilo Scannella, Fabrizio Serena, Sergio Vitale and Fabio Fiorentino

Fishes 2022, 7(3), 136; https://doi.org/10.3390/fishes7030136 - 07 Jun 2022

Cited by 13 | Viewed by 2689

Abstract

Elasmobranchii (sharks and rays), which have peculiar and vulnerable life-history traits, are highly threatened by fishing activities. Indeed, between 53% and 71% of Mediterranean elasmobranch species are at risk of extinction. In this context, using the abundance MSY (AMSY) model, the present study provides an assessment of 20 batoids and 16 shark species in the Strait of Sicily, sampled during a bottom trawl survey from 1995 to 2020. Overall, the outputs underline a progressively improving condition for shark and ray assemblages of both shelf and eurybathic zones. As for slope-dwelling species, a horseshoe-shaped dynamic, characterized by a progressive decrease in relative harvesting pressure and an increase in relative biomass followed by an increase in fishing pressure and decrease in biomass, was detected. The dynamics of the Elasmobranchii living in the Strait of Sicily appear to be affected by changes in the fishing patterns of trawlers, showing a shift from shallow water to bathyal fishing grounds and targeting deep-water red shrimp. In this context, it seems wise to limit the impact of deep-water fisheries on Elasmobranchii by reducing fishing efforts and implementing ad hoc management measures aimed at safeguarding these vulnerable species. Full article

(This article belongs to the Special Issue Cartilaginous Fishes: Stock Assessment and Population Dynamics)

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