Prehrana brgljuna Engraulis encrasicolus (Linnaeus, 1758) tijekom mrijesta u istočnom dijelu Jadranskoga mora

The objective of this study was to determine, both quantitatively and qualitatively, the variability in the diet of the anchovy, Engraulis encrasicolus, during its spawning period. Samples were obtained from commercial purse seine catches (April 2014 – September 2016) from coastal and offshore fishing areas of different trophic states and zooplankton composition over the eastern Adriatic Sea. In general, decapod larvae comprise the main source of diet during the anchovies’ spawning period in terms of frequency and abundance, followed by calanoid copepods. The main copepod prey that was identified for anchovy along the eastern Adriatic coast was calanoid Temora stylifera, followed by Oncaeid copepods and Corycaeidae. Although no significant differences in diet composition regarding the anchovy’s size was observed, the contribution of copepods decreased in larger individuals, and were gradually substituted by large crustaceans - decapods, euphausiids, mysids and amphipods. However, a significant difference in prey composition between coastal and offshore areas was observed (global R=0.164, p<0.05). Beside adult copepods, offshore water anchovy fed mainly on decapod larvae and their megalopa stage, and amphipods. In the stomach of the fish caught in the coastal waters, higher contributions of euphausiids, mysids and fish eggs were observed. Prey diversity was greater in the stomach of specimens caught offshore (H’=0.59) than in the costal Adriatic waters (H’=0.40).Cilj ovog rada bio je utvrditi kvantitativnu i kvalitativnu varijabilnost u prehrani brgljuna Engraulis encrasicolus tijekom mrijesta. Uzorci iz komercijalnih ulova plivaricom (travanj 2014 – rujan 2016), obuhvatili su ribolovna područja obalnog i otvorenog mora duž istočne obale Jadrana, različitog trofičkog stanja i sastava zooplanktona. Ličinke deseteronožaca općenito su glavni izvor hrane tijekom mrijesta brgljuna, a prate ih kalanoidni veslonošci. Unutar veslonožaca najzastupljenija je bila vrsta kalanoida Temora stylifera, a slijede veslonošci skupine Oncaea i porodica Corycaeidae. Premda nisu utvrđene značajne razlike u sastavu prehrane u odnosu na dužinu ribe, udio veslonožaca smanjio se porastom dužine brgljuna, a postupno su ih nadomještali veliki rakovi - deseteronošci, eufazidi, rašljonožci i rakušci. Međutim, uočena je značajna razlika u sastavu plijena između obalnog i otvorenog mora (globalni R = 0.164, p <0.05). Pored odraslih veslonožaca, brgljun otvorenog mora hranio se uglavnom ličinkama deseteronožaca i njihovih megalopa stadija te rakušci. U želucu ribe ulovljene u obalnim vodama primijećen je veći doprinos eufauzida, rakušcima i ribljih jaja. Raznolikost plijena bila je veća u želucima jedinki ulovljenih u otvorenim vodama (H’=0.59) nego u obalnom dijelu Jadrana (H’=0.40)

Ingresija hidromeduse Neotima lucullana (della chiaje, 1822) u ekosustavu estuarija rijeke Neretve (jugoistočni Jadran, Hrvatska)

Hydromedusa Neotima lucullana is an endemic species of the Mediterranean Sea. In this study we document the first numerous and permanent occurrence of N. lucullana in the estuary of the Neretva River, an unusual habitat for this typical marine species. We provide COI barcode sequence of this species, which is also first genetic sequence ever published of N. lucullana. Weekly data on the occurrence and abundance of N. lucullana were obtained from reports and records of autonomous divers and local fishermen in the area from Opuzen to Metković from mid-June to the end of October 2021. The individuals were always located in the layer above the bottom with salinity between 35.2 and 38.2. The diameters of the jellyfish bells ranged from 15 mm to 72 mm, most of them between 40 mm and 58 mm. Differential development of the gonads was observed in all specimens larger than 25 mm. In mid-June, the specimens were common but solitary. A week later, the jellyfish were more frequent and in smaller aggregations. From late June to mid-September, the jellyfish were constantly observed in larger aggregations. Toward the autumn, the number of individuals gradually decreased, and by the last week of October, only single individuals were observed. Our results indicate significant changes in the ecosystem of the Neretva estuary and confirm the observed composition of zooplankton communities dominated by marine species in summer and autumn.Hidromeduza Neotima lucullana je endemska vrsta Sredozemnog mora. Ovim istraživanjem dokumentiramo prve zapise o brojnoj i dugotrajnoj pojavi meduze N. lucullana u estuariju rijeke Neretve, neobičnom staništu za ovu tipično morsku vrstu. U sklopu ovog istraživanja dobivena je sekvenca podjedinice i citokrom oksidaze (COI), što je ujedno i prva genetička sekvenca ikad objavljena vrste N. lucullana. Tjedni podaci o pojavi i brojnosti N. lucullana dobiveni su na osnovi izvještaja i zapisa autonomnih ronilaca i lokalnih ribara na području od Opuzena do Metkovića od sredine lipnja do kraja listopada 2021. Jedinke meduza su uvijek bile u sloju iznad dna unutar vrijednosti saliniteta između 35,2 i 38,2. Promjer zvona meduza kretao se od 15 mm do 72 mm, glavnina između 40 mm i 58 mm. Diferencijalni razvoj spolnih žlijezda uočen je kod svih primjeraka većih od 25 mm. Sredinom lipnja jedinke su bile uobičajene, ali prisutne pojedinačno. Tjedan dana kasnije, meduze su bile često viđene i u manjim skupinama. Od kraja lipnja do sredine rujna, meduze su bile prisutne u većim agregacijama. Broj jedinki postupno se smanjivao prema jeseni i samo pojedinačni primjerci bili su uočeni tijekom posljednjeg tjedna listopada. Naši rezultati ukazuju na znatne promjene ekosustava donjeg toka rijeke Neretve što potvrđuje zabilježen sastav zooplanktonskih zajednica u kojima dominiraju morske vrste tijekom ljeti i jeseni

Copepod Diel Vertical Distribution in the Open Southern Adriatic Sea (NE Mediterranean) under Two Different Environmental Conditions

Diel vertical migration of the copepod the community was investigated in the open South Adriatic, in June 2020 and February 2021, under two very different hydrographical conditions. The influence of a winter wind-induced mixing event on copepod vertical migration at the species level was determined for the first time and compared to the situation in June when pronounced thermal stratification was observed. The samples were collected during a 24 h cycle in four depth layers from the surface down to 300 m depth, using a Nansen opening&ndash;closing net with 250-&micro;m mesh size. In winter, the bulk of the copepod population remained in the epipelagic zone (0&ndash;100 m) over the entire 24 h cycle, with calanoids remaining the dominant group. An increasing trend of copepod standing stocks from midnight to early morning in the surface layer found in June is in agreement with previous records of copepod day&ndash;night variations in the Mediterranean Sea. Day&ndash;night differences in diversity and the number of taxa of the epipelagic area were more pronounced in June, confirming the higher intensity of diel vertical migration in summer. Although the epipelagic community was composed of numerous weak diel vertical migrant species, for the majority of investigated copepod taxa, migration patterns differed between the environmentally contrasting seasons. A multivariate non-metric analysis showed that the copepod community was strongly affected by temperature, thus exhibiting a clear seasonal structure

Composition and diel vertical distribution of euphausiid larvae (calyptopis stage) in the deep southern Adriatic

Summary: Diel changes in the vertical distribution and abundance of calyptopes were studied in the deepest area of the southern Adriatic over four seasons (July 2003, February 2004, October 2004, April 2009). Temperature variations were limited to the upper 100 m and salinity variations were small. Of previously known adult euphausiid species – 12 for the Adriatic (Gangai et al., 2012) and 13 for the Mediterranean (Mavidis et al., 2005) – calyptopes of 11 species of euphausiids were recorded. Abundance of calyptopes of all species was the highest in spring. Species were characterized according to their mean depth: surface (0–50 m), sub-surface (50–200 m), mesopelagic (200–800 m), or bathypelagic (800–1200 m) and vertical dispersion (scattered or non-scattered). Four diel patterns emerged: (i) nocturnal ascent to upper layers (Euphausia brevis, E. hemigibba, E. krohnii, Nematoscelis megalops, N. couchii), (ii) migration to upper layers at middle of the day and at night, and descent during the morning and evening (Stylocheiron maximum – only winter), (iii) weakly-migrating or non-migrating (S. longicorne), (iv) irregular migration independent of the day/night cycle (S. abbreviatum, S. maximum – during spring, summer and autumn, T. aequalis). Keywords: Euphausiid larvae, Mediterranean Sea, Secondary production, Vertical distribution, Weighted mean dept

JellyCo - A simple imaging system for in situ quantification of jellyfish

Trabajo presentado en el 1st Meeting of the Iberian Ecological Society y XIV AEET Meeting (SIBECOL 2019), celebrados en Barcelona del 4 al 7 de febrero de 2019.Gelatinous zooplankton (cnidarians, ctenophores, tunicates)are gaining increasing interest from researchers and the general public. This is due to their ability to form large blooms that may interfere with human activities and have a strong impact on the affected ecosystems. Early detection and monitoring of such organisms is essential for effective management and mitigation of jellyfish outbreaks. Considering the impacts that jellyfish may have, there is surprisingly little data on their distribution and abundance, that is at least in part due to problems with the sampling and monitoring of these fragile organisms.This study was partially founded by the Slovenian Research Agency and Slovenian Ministry of Higher Education, Science and Technology (Program P1-0237, project “Raziskovalci-2.0-NIB-529024”),the project Medusas Baleares UCA2014020031,the Croatian Science Foundation under the project IP-2014-09-2945 andthe Mljet National Park.Peer reviewe

Long-term Monitoring of Carnivorous Gelatinous Macrozooplankton in the Area of Dubrovnik-Neretva County (Croatia)

In the southern part the Adriatic, gelatinous macrozooplankton fauna is poorly known compared to the other taxa. Therefore, our goal was to collect and systematize all available phenological data and abundances of gelatinous organisms based on scientific surveys from 1996 to 2020 and a ”citizen science“ sighting program in the southern Croatian waters. The inter-annual variability and seasonality of planktonic Cnidaria and Ctenophora were described. A total of 590 reports was received from citizens, which summed up to result in 870 data together with the scientists’ records. In total, 15 species were recorded. Of these, scyphomedusa Pelagia noctiluca accounted for 34 %, followed by ctenophora Cestum veneris (19 %) and the scyphomedusa Cothylorhiza tuberculata (17 %). Mass occurrence was most frequently found in P. noctiluca and then in C. tuberculata and C. veneris. Isolated mass occurrence was recorded for the freshwater hydromedusa Craspedacusta sowerbii, found in Lake Kuti near the mouth of the Neretva River, and for the scyphomedusa Aurelia cf. solida. The three species A. solida, Mnemiopsis leidyi and C. sowerbii are not native to European waters. Considered that alien species are invading the Adriatic Sea and human impact and global warming are increasing, it is crucial to carefully monitor the occurrence of gelatinous zooplankton taxa and to conduct studies focused on deciphering their ecological impact in marine ecosystems. Therefore, our empirical analysis of 25 years of observations provides essential information on the variation of gelatinous zooplankton in the Southern Adriatic region

The Distribution of <i>Pseudodiaptomus marinus</i> in European and Neighbouring Waters—A Rolling Review

Among non-native copepods, the calanoid Pseudodiaptomus marinus Sato, 1913 is the species probably spreading at the fastest pace in European and neighbouring waters since its first record in the Adriatic Sea in 2007. In this contribution, we provide an update on the distribution of P. marinus in the Mediterranean and Black Seas, along the Atlantic coasts of Europe, in the English Channel and in the southern North Sea. Starting from a previous distribution overview, we include here original and recently (2019–2023) published data to show the novel introduction of this species in different geographical areas, and its secondary spreading in already colonised regions. The picture drawn in this work confirms the strong ability of P. marinus to settle in environments characterised by extremely diverse abiotic conditions, and to take advantage of different vectors of introduction. The data presented allow speculations on realistic future introductions of P. marinus and on the potential extension of its distribution range

Copernicus Marine Service Ocean State Report, Issue 5

International audienc