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- Exploitation status and stock assessment of the smooth clam Callista
chione (Linnaeus, 1758) in the northern Alboran Sea (GSA01-W Mediterranean
Sea)
Authors: JORGE BARO, TERESA GARCIA, JAVIER URRA, MATIAS LOZANO, JOSE LUIS RUEDA
Pages: 1 - 10
Abstract: The smooth clam, Callista chione (Linnaeus, 1758), is a venerid bivalve widely appreciated in southern Spain where it represents the top commercial bivalve species in terms of landings and economic value. In this area, a total of 223 artisanal boats (68% of the artisanal fleet) are involved in shellfishing targeting bivalve molluscs, including the smooth clam. The artisanal mechanised dredging that targets C. chione in the northern Alboran Sea is described and the current exploitation status of its populations is analysed. A surplus-production model was run using ASPIC and used to assess the temporal variation in the levels of fishing for this bivalve throughout the study period (2002-2015), as well as to suggest conservation reference points that could guarantee the sustainable exploitation of this resource. During the study period, the maximum C. chione catch was registered in 2003 (306 t) and the minimum in 2006 (93 t). The ASPIC model for C. chione stock suggests that a Maximum Sustainable Yield (MSY) of 216 t could be produced from a total stock biomass of 983 t (Bmsy) at a fishing mortality rate of total biomass of 0.22 (Fmsy), with B/Bmsy and F/Fmsy values of 1.34 and 0.82, respectively, indicating that the stock is approaching good status.
PubDate: 2018-05-23
DOI: 10.12681/mms.14193
Issue No: Vol. 19, No. 1 (2018)
- Fish assemblages along the coasts of Tunisia: a baseline study to assess
the effectiveness of future Marine Protected Areas
Authors: EMNA BEN LAMINE, PAOLO GUIDETTI, MOHAMED SALAH ROMDHANE, PATRICE FRANCOUR
Pages: 11 - 20
Abstract: The present study investigated coastal fish assemblages, using Underwater Visual Census (UVC) transects, in Tunisia (south Mediterranean basin). The rationale behind this work is to get i) a suggestive evidence about the status of fish assemblages, and ii) baseline data at 3 locations in Tunisia where 3 MPAs will be established, before the implementation of protection measures. At each location, we used a sampling design where fish censuses were performed in two types of zone: zones that will be inside MPAs, and zones that will remain outside. On the whole, 49 taxa belonging to 19 families were censused. Data reveal clear symptoms of overfishing, especially in terms of dominance of small- and medium-sized individuals of commercially relevant species. Our analyses, moreover, did not show any significant difference in whole fish assemblage structures (considering both density and biomass), patterns of average species richness, total fish density and biomass, density and biomass of different trophic categories of fishes, size distribution of commercially relevant species, between future-protected and unprotected zones. Overall, results suggest that 1) current fish assemblages at the three studied locations are likely to be seriously impacted by fishing activities, and 2) these data could be used as reliable baselines to assess the effectiveness of protection measures within the MPAs that will be established in the future. Our study is the first in Tunisia, and in North African coasts, that assessed distribution patterns of coastal fish assemblages by means of UVC, using a formal spatially replicated sampling design for resource management.
PubDate: 2018-05-23
DOI: 10.12681/mms.14206
Issue No: Vol. 19, No. 1 (2018)
- Seasonal dynamics of small-scale fisheries in the Adriatic Sea
Authors: FABIO GRATI, ADMIR ALADZUZ, ERNESTO AZZURRO, LUCA BOLOGNINI, PIERLUIGI CARBONARA, MIMOZA ҪOBANI, FILIPPO DOMENICHETTI, BRANKO DRAGICEVIC, JAKOV DULCIC, MIRKO ÐUROVIC, ZDRAVKO IKICA, ALEKSANDAR JOKSIMOVIC, JERINA KOLITARI, BOJAN MARCETA, SANJA MATIC-SKOKO, DARIO VRDOLJAK, GIUSEPPE LEMBO, ALBERTO SANTOJANNI, MARIA TERESA SPEDICATO, NIKA STAGLICIC, NEDO VRGOC, NIJAZ ZEREM, ENRICO ARNERI, LUCA CERIOLA, NICOLETTA MILONE
Pages: 21 - 35
Abstract: The main aim of the present study is to increase the knowledge on the seasonal dynamics of the set gears used by Adriatic small-scale fisheries (SSFs) through the collation of data (landings, fishing effort, composition of catches, length-frequency distributions of target species and economic value of landings) on target species,. The study focused on the three set gears mainly used in the basin: gillnets, trammel nets and traps. The results confirmed that SSFs are diverse, complex and dynamic, representing an economic and social engine and providing seafood and employment to local economies. In the Adriatic Sea, SSFs exploit coastal fishing grounds where the seasonal fluctuations of the physical and chemical parameters of the water column strongly influence the occurrence of the different species. Because of this, many different types of set gears are currently used to catch a pool of target species over the year. Fishermen use more than one set gear during the year and tend to increase the fishing effort when the target species concentrate inside the coastal areas during the recruitment or the spawning season. Accordingly, landings reached the highest values during such periods and often include a large portion of juveniles and/or spawners. The study highlighted that the lack of appropriate data and complete statistics is still one of the main constraints for most of the Adriatic coastal countries, as few countries have in place routinely monitoring programs while others are dealing mostly with estimates. These gaps often have the effect of marginalizing and undervaluing the real role of SSFs in a Blue Growth process.
PubDate: 2018-05-23
DOI: 10.12681/mms.2153
Issue No: Vol. 19, No. 1 (2018)
- Spatial distribution of suspended solids during short-term high river
discharge in the Bay of Koper, northern Adriatic Sea
Authors: ROK SOCZKA MANDAC, DUŠAN ŽAGAR
Pages: 36 - 47
Abstract: The Bay of Koper (BoK) located in the Gulf of Trieste (northern Adriatic Sea) is subject to a variety of anthropogenic influences; pollutants from inland are transported to the sea by the local rivers. The impact of high river discharge on suspended solids distribution was assessed by analysing results of an extensive measurement campaign conducted during two episodes of river flooding. The spatial analysis demonstrated the area influenced by fresh water and the distribution of inorganic suspended solids (ISS). The results were then used to calibrate the PCFLOW3D model and to simulate two episodes. A correlation was identified between the measurements and short-term simulations found in the central part of the bay. The results confirm the methods and the model used in this study to be appropriate for studying complex suspended solids processes in coastal areas.
PubDate: 2018-05-23
DOI: 10.12681/mms.2141
Issue No: Vol. 19, No. 1 (2018)
- Insights into the species diversity of the genus Sargassum (Phaeophyceae)
in the Mediterranean Sea, with a focus on a pre-viously unnoticed taxon
from Algeria
Authors: MOUNIA AOUISSI, LOUIZA NESRINE SELLAM, CHARLES F. BOUDOURESQUE, AURELIE BLANFUNÉ, FARID DERBAL, HOCINE FRIHI, MICHELE PERRET-BOUDOURESQUE, CHAFIKA REBZANI-ZAHAF, MARC VERLAQUE, THIERRY THIBAUT
Pages: 48 - 57
Abstract: Nine currently accepted species of the genus Sargassum (Phaeophyceae) have been recorded from the Mediterranean Sea: S. acinarium, S. desfontainesii, S. flavifolium, S. furcatum, S. hornschuchii, S. muticum, S. ramentaceum, S. trichocarpum and S. vulgare. Two of them, S. desfontainesii and S. furcatum, are Atlantic species, the Mediterranean range of which is restricted to the Alboran Sea, close to the Strait of Gibraltar. Three species, S. hornschuchii, S. ramentaceum and S. trichocarpum are endemic to the Mediterranean. The presence of S. flavifolium in the Mediterranean, a north-eastern Atlantic species, is at least in part based upon a misidentification and therefore requires confirmation. A taxon collected near Algiers and Annaba (Algeria), here referred to as ‘Sargassum sp. from Algeria’, although sharing most characters with S. flavifolium, also presents some distinctive characters. In the absence of genetic data, confirming or not its taxonomic value, and in the lack of studies on the herbaria containing the types of many species currently considered as synonyms of S. flavifolium, but which are possible candidates for accommodating the Algerian specimens, the authors prefer a conservative approach. They do not describe a new species, which would be premature, but draw attention to a taxon which may be more widely distributed in the Mediterranean rather than solely along the Algerian coasts.
PubDate: 2018-05-23
DOI: 10.12681/mms.14079
Issue No: Vol. 19, No. 1 (2018)
- The dynamics of phytobenthos and its main drivers on abrasion platforms
with vermetids (Alicante, Southeastern Iberian Peninsula)
Authors: MARC TERRADAS FERNÁNDEZ, CARLOS BOTANA GÓMEZ, MIGUEL VALVERDE URREA, JOSÉ JACOBO ZUBCOFF, ALFONSO RAMOS ESPLA
Pages: 58 - 68
Abstract: Abrasion platforms with vermetids shape unique seascapes and biotic assemblages that characterize several of the warm Mediterranean coasts. The composition, structural and seasonal dynamics of the platforms’ phytobenthos were examined at two Southeast Iberian locations through non-destructive sampling. The patterns observed were linked with environmental variables and grazers’ coverage, and we assessed their possible influence. Structural descriptors α-diversity and β-diversity were applied, pointing that depth and season-related variables were the major influencing drivers. Higher α-diversity and β-diversity values during winter and spring coincided with the production optimum of the community. A greater average water depth influences the abundance of both midlittoral and infralittoral taxa. The strong resemblance between the phytobenthos of these vermetid platforms and that on similar platforms in the Eastern and Central Mediterranean Sea suggests that these are affected by the same structuring mechanisms.
PubDate: 2018-05-23
DOI: 10.12681/mms.14143
Issue No: Vol. 19, No. 1 (2018)
- By-catch in the commercial beam trawl fishery for Rapa Whelk in the Black
Sea
Authors: AHMET RAIF ERYASAR, YUSUF CEYLAN, GOKTUG DALGIC, TUNCAY YESILCICEK
Pages: 69 - 78
Abstract: In this work, the by-catch was investigated in commercial beam trawls used in the rapa whelk (Rapana venosa) fishery, in trials at sea between September 1, 2015 and April 30, 2016. Four commercial boats using beam trawls were chartered and catch data was collected from a total of 87 hauls. Hauls were performed between 7.1–28.3 meters deep for a duration of 20–77 minutes and haul speed varied between 1.4 – 2.7 knots. A total of 28 by-catch species were identified, which amount in average to 11.4% of the total number of specimens in the by-catch. Two different groups were identified in the by-catch (G1: 7-18 m, G2: 19-26 m) according to depth. Although there is a reduction in the amount of by-catch for G2 group, no significant difference was found between groups (p>0.05). According to Generalized Additive Models (GAM) results, the variables affecting the by-catch amount were identified as fishing area, depth, haul duration, and amount of captured rapa whelk (p<0.01). In addition, a large proportion of immature individuals of striped venus clams (Chamelea gallina), blood cockles (Anadara kagoshimensis), Mediterranean mussels (Mytilus galloprovincialis) and wedge clams (Donax trunculus) were caught as by-catch during the study. Finally, the impact of commercial beam trawls on the demersal macrofauna is discussed.
PubDate: 2018-05-23
DOI: 10.12681/mms.13873
Issue No: Vol. 19, No. 1 (2018)
- Reconciling Trends of Mean Trophic Index and Mean Temperature of the Catch
in the Eastern Mediterranean and Black Seas
Authors: ÇETIN KESKIN, DANIEL PAULY
Pages: 79 - 83
Abstract: The mean trophic level, i.e., the Mean Trophic Index (MTI) and Mean Temperature of the Catch (MTC) were estimated for Turkish waters in the Eastern Mediterranean and the Black Sea based on the reconstructed marine fisheries catches (consisting of N = 88 species and/or higher taxa) of in Turkish waters for the year 1950 to 2010. The MTI decreased in both regions of Turkey, following expectations, but the MTC showed different trends in these two regions. It increased (by 0.48 °C·decade-1), along with the SST in the Eastern Mediterranean, while it fluctuated in the Black Sea. This fluctuating behaviour, however, was similar to the fluctuating tendency of SST in the Black Sea. This suggests that the MTI and MTC can be relied upon as indicators of fisheries impacts on ecosystems, and of the impact of changing temperatures on fisheries, respectively.
PubDate: 2018-05-23
DOI: 10.12681/mms.1882
Issue No: Vol. 19, No. 1 (2018)
- Shedding light on an East-Mediterranean mesophotic sponge ground community
and the regional sponge fauna
Authors: TAL IDAN, SIGAL SHEFER, TAMAR FELDSTEIN, RUTH YAHEL, DOROTHEE HUCHON, MICHA ILAN
Pages: 84 - 106
Abstract: Sponges are a diverse and abundant phylum, globally inhabiting many hard-bottom habitats. However, data on the East-Mediterranean sponge communities are scarce, outdated, and limited to the shallow waters. This study sought to expand the knowledge of the poriferan fauna along the Mediterranean shore of Israel. A newly-discovered mesophotic sponge ground at ~100 m depth was studied using a remotely-operated vehicle (ROV), in addition to shallow-water surveys conducted by scuba diving. In the mesophotic ecosystem, sponges, serving as environmental engineers, create complex 3D structures that attract invertebrates and fish. The results of the quantitative survey of this mesophotic sponge ground reveal that it maintains a rich and diverse community with an estimated 63 species, and a high sponge percent coverage (~35%). Several of the mesophotic species are documented for the first time from the Levant basin, while others might be novel species. Here we identified over 100 sponge species along the Mediterranean coast of Israel, 33 of which were sampled from the mesophotic sponge ground. The updated sponge list supports the hypothesis that the Levantine sponge diversity is not as species-poor, compared to other parts of the Mediterranean Sea, as has previously been considered. In addition, shallow and mesophotic sponge community compositions were found to only partially overlap. Moreover, the latter harbors some species that have disappeared from the shallow habitats, and only a few species thrive along the entire depth range. We suggest that mesophotic sponge grounds may serve as refugia for species stressed by the rising temperatures in shallow waters and should be protected from anthropogenic influences such as oil and gas drilling.
PubDate: 2018-05-23
DOI: 10.12681/mms.13853
Issue No: Vol. 19, No. 1 (2018)
- Assessing the socio-economic impacts of priority marine invasive fishes in
the Mediterranean with the newly proposed SEICAT methodology
Authors: MARIKA GALANIDI, ARGYRO ZENETOS, SVEN BACHER
Pages: 107 - 123
Abstract: The assessment of impacts of alien species is one of the most critical steps for the prioritisation of policy and management actions and this requires assessment schemes that can compare impacts across different taxa, ecosystems and socio-economic contexts. The Environmental and Socio-Economic Impact Classification of Alien Species (EICAT and SEICAT) are two methodologies that facilitate such comparisons. They classify alien taxa along a 5-level, semi-quantitative scale based on the magnitude of their impacts on the environment and human well-being, respectively. In this study, we applied both protocols to seven invasive marine fishes that that are already considered “high-risk” and have been singled out for monitoring in relation to fisheries in the Mediterranean (Plotosus lineatus, Pterois miles/volitans, Fistularia commersonii, Lagocephalus sceleratus, Siganus rivulatus/Siganus luridus and Saurida lessepsianus). Here, we focus in particular on their socio-economic impacts. By systematically reviewing the published literature and scoring the demonstrated impacts we show that the taxa with the highest environmental impacts (Major) are P. miles/volitans and the two siganids. In contrast, L. sceleratus had the highest socio-economic impact (Moderate) and highest number of impact records. The high and uniform densities of P. lineatus caused widespread, albeit less severe, impacts in the invaded areas. Human activities that are primarily affected by the selected taxa are commercial and recreational fishing and other recreational uses of the sea through impacts on, mainly, material assets and human health. We found significant data gaps regarding the species’ environmental impacts, especially relating to predation, and make specific recommendations for future research. The links between environmental and socio-economic impacts, especially their cultural dimensions, are poorly documented and require novel approaches. Surveys specifically adapted to capture the distinction between socio-economic impact classes would strengthen our confidence in the assessments and better inform prioritisation and decision-making.
PubDate: 2018-05-23
DOI: 10.12681/mms.15940
Issue No: Vol. 19, No. 1 (2018)
- First record of exotic Lysmatid shrimp Lysmata vittata (Stimpson, 1860)
(Decapoda: Caridea: Lysmatidae) from the Egyptian Mediterranean coast
Authors: KHALED MAHMOUD ABDELSALAM
Pages: 124 - 131
Abstract: The present study deals with first record of the alien Lysmatid shrimp Lysmata vittata (Stimpson, 1860) collected in April 2017, from the Egyptian Mediterranean Sea. A concise re-description supplied with illustrations, taxonomical remarks, habitat and distribution of the recorded species are provided.
PubDate: 2018-05-23
DOI: 10.12681/mms.15591
Issue No: Vol. 19, No. 1 (2018)
- Native, invasive and cryptogenic Ulva species from the Israeli
Mediterranean Sea: risk and potential
Authors: NIMROD KRUPNIK, GUY PAZ, JACOB DOUEK, EFRAIM LEWINSOHN, ALVARO ISRAEL, NAVA CARMEL, FRÉDÉRIC MINEUR, CHRISTINE A. MAGGS
Pages: 132 - 146
Abstract: The genus Ulva (Chlorophyta) is ubiquitous along Israeli Mediterranean shores where it has been studied extensively due to its important ecological role and potential value in biotechnology and aquaculture. Previous identifications of Ulva in Israel were based only on morphology. Here, we compare species found in 2002 and in 2014-2016. Analyses of ribulose-1,5-bisphosphate carboxylase/oxygenase (rbcL) and elongation factor 1-alpha (tufA) plastid genes (2014-2016 samples only), combined with morphological data, identified six Ulva species, three of which are new records for Israel and probably originate from the Indo-Pacific. Ulva compressa, rarely found in 2002, is now the most abundant species and exhibits two fairly distinct morphologies correlated with different haplotypes for both genes. Ulva fasciata was found more commonly in 2002 than in 2014-16, whereas the morphologically similar, and closely related, invasive species U. ohnoi seemed more frequent in recent samples. The finely branched tubular Ulva tepida was found in 2002 and 2015/16, and U. chaugulii and U. mediterranea were discovered for the first time in 2015/16. The changing Ulva flora of the Israeli Mediterranean may be correlated with major environmental changes including 3°C increase in sea surface temperatures over the last two decades, as well as a generally increasing prevalence of non-native species. The local Ulva species now found in Israel could be of value for various industrial uses.
PubDate: 2018-05-23
DOI: 10.12681/mms.2104
Issue No: Vol. 19, No. 1 (2018)
- Structure and temporal dynamics of a seaweed assemblage dominated by the
invasive lineage 2 of Asparagopsis taxiformis (Bonnemaisoniaceae,
Rhodophyta) in the Alboran Sea
Authors: MARIANELA ZANOLLA, RAQUEL CARMONA, JULIO DE LA ROSA, MARÍA ALTAMIRANO
Pages: 147 - 155
Abstract: Asparagopsis taxiformis is a rhodophycean species composed of six genetic lineages, one of which is considered a relevant invasive component of the Mediterranean flora. In the present study we describe seasonal changes of the structure and biomass of the native community associated to Asparagopsis taxiformis in Granada (Southern Spain). Native community was represented by 18 Rhodophyta, 3 Chlorophyta and 4 Ochrophyta species. Biomass was dominated by A. taxiformis and Halopteris filicina. While in January A. taxiformis accounted for only 16% of the community biomass, an explosive dominance was observed only two months later, representing more than 90% of the algal biomass. Furthermore, low and generally stable values of species richness, Shannon’s diversity index and evenness were recorded during the study period. Given that A. taxiformis gametophytes are present year round, they are likely to pose a constant stress to native community development. This survey provides baseline information of macroalgal community structure useful for further studies to assess the true impact of the invasive lineage of A. taxiformis.
PubDate: 2018-05-23
DOI: 10.12681/mms.1892
Issue No: Vol. 19, No. 1 (2018)
- Biodiversity changes along the Algerian coast (Southwest Mediterranean
basin): from 1834 to 2017: A first assessment of introduced species
Authors: SAMIR GRIMES, MOULOUD BENABDI, NADHERA BABALI, WAHID REFES, NAWAL BOUDJELLAL-KAIDI, HALIMA SERIDI
Pages: 156 - 179
Abstract: “Introduced” species of the Algerian coast remains the most undocumented issue in the Mediterranean Sea. Only few studies were dedicated to Introduced species due to the lack of taxonomists. In-depth research on Introduced species along the Algerian coast should provide new data that could explain the spreading mechanisms in the southwestern part of the Mediterranean basin particularly near the Alboran Sea. Introduced species among other related research; of which the outcome is expected in the next few years, is in progress in the southwest Mediterranean basin. The aim of this work is to provide an inventory of available data pertaining to marine species “introduced” in Algerian waters, whether these species were introduced intentionally or accidentally. This large number of Introduced species records covers the period from 1834 to December 2017. Seventy “Introduced” species have been recorded along the Algerian coast, composed by 55.7% true aliens25.7 % range expanding species, 15.7% cryptogenic species and 2,9% vagrant species, with a clear domination of fish (38.57%) and macroalgae (30%). Approximately 348 introduction events have been reported; 64,9 % of them belong to macroalgae and one sighting out of two is done in the central region. The distribution and the status of introduced species in Algeria were evaluated. In total, 20% of the Introduced species can be considered as established along the Algerian coast, in particular the macrophyta, Codium fragile and Ulva lactuca as well as the cryptogenic species, Oculina patagonica, while Asparagopsis armata, A. taxiformis and Caulerpa cylindracea are considered as invasive.
PubDate: 2018-05-23
DOI: 10.12681/mms.13824
Issue No: Vol. 19, No. 1 (2018)
- Distribution of Engraulis encrasicolus eggs and larvae in relation to
coastal oceanographic conditions (the South-western Adriatic Sea case
study)
Authors: SARA MALAVOLTI, ANDREA De FELICE, ILARIA COSTANTINI, ILARIA BIAGOTTI, GIOVANNI CANDUCI, FEDERICA GRILLI, MAURO MARINI, VALENTINA TIRELLI, DIEGO BORME, VINCENZO CAPUTO BARUCCHI, IOLE LEONORI
Pages: 180 - 192
Abstract: Identification of potential spawning and nursery areas of European anchovy (Engraulis encrasicolus) represents an essential step in the management of a resource which is of fundamental importance both for fishery and pelagic trophic web. Egg and larvae occurrence from ichthyoplankton surveys (2012 - 2015) in the South Western Adriatic Sea were examined to understand the mechanisms that control their distribution. Egg and larvae densities varied through the years with the highest values recorded in 2012 and the lowest in 2014. Positive correlations between eggs and larvae with zooplankton were observed. When quotient analysis was used to find relations with environmental and biological variables, the results pointed out an egg preference for depth between 91 and 120 m and an avoidance between 11 and 30 m. Moreover, egg avoidances for high values of chlorophyll-a (> 0.52 mg m-3) and low values of zooplankton biomass (< 199 mg m-2) were highlighted. On the other hand, different ranges of habitat preferences and avoidances were observed for larvae: preference range of depth between 11 and 60 m and avoidance > 151 m; preference for high zooplankton biomass (> 1000 mg m-2) and avoidance for low biomass (< 299 mg m-2). These correlations and the quotient values suggest that egg and larvae distribution in the South-Western Adriatic Sea is mainly driven by food availability and depth.
PubDate: 2018-05-23
DOI: 10.12681/mms.14402
Issue No: Vol. 19, No. 1 (2018)
- Parasites affect hemocyte functionality in the hemolymph of the invasive
Atlantic blue crab Callinectes sapidus from a coastal habitat of the
Salento Peninsula (SE Italy)
Authors: PATRIZIA PAGLIARA, GIORGIO MANCINELLI
Pages: 193 - 200
Abstract: The blue crab Callinectes sapidus is an invasive alien species in the Mediterranean Sea. In native habitats, it is subjected to mortalities determined by different pathogens, including the dinoflagellate Hematodinium perezi, a parasite also affecting other brachyuran species. Specifically, Hematodinium-associated disease is acknowledged worldwide as an emerging infection for commercially important crustacean species, but the general diffusion in wild species is unknown. Here, a preliminary screening in C. sapidus hemolymph as well as in three indigenous crabs captured in SE Italy, evidenced the presence of unidentified protozoans in more than 70% of specimen, but the number of suspected Hematodinium cells was very low. The parasites occurrence affected C. sapidus hemocytes functionality, interfering with their role in innate immunity (i.e. phagocytosis or DOPA production). More studies are necessary in order to verify the impact of this alien brachyuran on invaded ecosystems as mediated by the spread of parasites and other pathogens.
PubDate: 2018-05-24
DOI: 10.12681/mms.13886
Issue No: Vol. 19, No. 1 (2018)
- A non-invasive manual method for the assessment of pregnancy in female
Scyliorhinus canicula catsharks
Authors: MERCEDES HOF, RENATE I. DAHLKE, THOMAS DANDEKAR, MARTIN KALTDORF, LOTHAR A. BECK
Pages: 201 - 208
Abstract: Enhanced survival of oviparous shark populations can rely on only one easily applicable method. We tested a powerful method to retrieve egg cases from dead oviparous females at the fish market which is non-invasive. We approved this method for Scyliorhinus canicula and Scyliorhinus stellaris (smallspotted catshark and Nursehound) in Valletta, Malta in 2014. Here, catsharks are landed in whole, whereas in many other Mediterranean countries sharks are already eviscerated when brought ashore. Saving egg cases bears the grateful opportunity to rescue shark embryos and this then helps again to restore fish stocks. The common work flow of fishermen is to throw away the egg cases when eviscerating the shark and so the embryos were left in the bin to die. To apply a non-invasive method is very important at fish markets where sharks are landed in one piece as fish brokers do not tolerate many dissections. So, our goal was to detect pregnant females with maximum accuracy and dissect only females with egg cases inside. Formerly, the common method used by members of Sharklab-Malta was to dissect females more or less randomly based on only two parameters (i) a total length above 40cm and (ii) a relatively corpulent body shape. This was not effective as many females were dissected without containing egg cases. This led to the more problematic fact that pregnant individuals were not found and so their offspring died in the end. The basic concept in our newly tested method is based on using a fixed touching pattern which allows to screen the belly of all females available simply by hand. To screen one female only 2 seconds are needed, and this works surprisingly well. We called this method “gotIt” simply because we got all available egg cases and could save all embryos. A validation underpinned the success and showed that gotIt works with 100% accuracy. After rescuing the egg cases they were transported to an aquarium. Egg cases were attached to a lanyard by their tendrils and left for development in the tank for 3-6 months (depending on their initial developmental stage at the fish market) at a water temperature of 15-19°C. After hatching, sharks were fed with squid and released into the sea. The number of rescued embryos arose significantly from five to above hundreds of shark pups which were saved and released by applying gotIt. Additionally, fishermen can be encouraged to use this method, as awareness programs can be promoted to encourage consumption of this sustainable fish, which can therefore increase the marketable prices. Widely applied, gotIt can help to preserve oviparous shark populations at fish markets where sharks are landed whole.
PubDate: 2018-05-30
DOI: 10.12681/mms.13838
Issue No: Vol. 19, No. 1 (2018)
- Molluscs collected with otter trawl in the northern Alboran Sea: main
assemblages, spatial distribution and environmental linkage
Authors: CRISTINA CIÉRCOLES, CRISTINA GARCÍA-RUIZ, MARIA GONZÁLEZ AGUILAR, JOSÉ M. ORTIZ DE URBINA GUTIERREZ, NIEVES MARIA LÓPEZ-GONZÁLEZ, JAVIER URRA RECUERO, JOSE LUIS RUEDA RUIZ
Pages: 209 - 222
Abstract: Molluscan assemblages of circalittoral and bathyal soft bottoms of the northern Alboran Sea were studied using an experimental otter trawl. Samples of fauna were collected from 190 hauls during four MEDITS surveys carried out in spring between 2012 and 2015 at depths ranging from 30 to 800 m. Measurements of water column variables (temperature and salinity) and sediment samples were taken in the same locations where faunistic sampling was carried out. A total of 101 species grouped in 55 families were recorded. Cephalopods were the most abundant group, with Abralia veranyi dominating in abundance, Octopus vulgaris in biomass and Illex coindetii and Todarodes sagittatus being the most frequently collected species. Multivariate analyses carried out separately with abundance data of demersal species, benthic species, bivalves, gastropods and cephalopods as well as of all molluscs, generally resulted in three main molluscan assemblages corresponding to a shelf assemblage (30-200 m depth), an upper slope assemblage (201-350 m depth), and a middle slope assemblage (351-800 m depth). PERMANOVA test revealed that significant differences of different groups of molluscs in relation to depth were more acute than to geographical sectors of the Alboran Sea (eastern, central, eastern and insular sectors). Abundance, biomass and species richness decreased with depth with a clear dominance of cephalopods in the slope. Significant geographical differences were mainly detected for demersal and benthic species as well as for gastropods and cephalopods between the insular sector (Alboran Island) and the western and eastern continental sectors. Both depth and temperature were the most influencing variables in the different CCA analyses using datasets of molluscs with different life styles and from different classes, but sedimentological variables displayed a more acute significant relationship with the benthic molluscs than with the demersal ones.
PubDate: 2018-05-31
DOI: 10.12681/mms.2124
Issue No: Vol. 19, No. 1 (2018)
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