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Povzetek: Studies on the feeding ecology of sympatric coastal species is important, especially in revealing different strategies to reduce competition. The aim of this study is to test the diet of littoral fish species with a non-destructive method, which does not necessitate the sacrifice of fish specimens. The clingfish Lepadogaster lepadogaster (Bonnaterre, 1788) was used to test this diet assessment method. Freshly caught specimens were delivered immediately to a specially designed box for collecting faecal pellets, supplied by an aerator. Clingfishes were left in the chambers for 24 hours to defecate. The pellets were carefully removed and fixed in 70% alcohol. The content of the pellets was analysed under stereomicroscope and prey items were determined and counted. The comparison with the existing studies showed similarity and consistency between their results, which proves the usefulness and applicability of the method for studying clingfish diet. The suitability of the proposed method was tested on related species L. candollei Risso, 1810, where all ingested prey items were also found and identified in faecal pellets, which confirms its effectiveness for diet analysis. A method of collecting faecal pellets immediately after defecation has proved to be more useful and effective than other nonlethal methods. After defecation, the specimens were released at the site where they were collected. Due to 100% survival as shown in this research, the proposed method is also suitable for studying the diet of rare and endangered fish species, and also coastal fish fauna in protected areas where traditional destructive sampling methods are not appropriate or allowed.
Ključne besede: non-destructive method, feeding habits, fish assemblage
Objavljeno v DiRROS: 19.03.2025; Ogledov: 535; Prenosov: 375
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Povzetek: Protein-based fish adhesives have historically been used in various bonding applications; however, due to the protein’s high affinity for water absorption, these adhesives become destabilized in high-moisture environments, resulting in reduced bondline strength and early failure. This limitation makes them unsuitable for industrial applications with higher demands. To address this issue, water-insoluble raw powder materials such as iron, copper, or zeolite were incorporated into natural fish adhesives. In this study, the hygroscopicity, dry matter content, thermal analysis (TGA/DSC), FT-IR spectroscopy, surface tension measurements, vapour permeability, and scanning electron microscope (SEM) of the modified adhesives were determined. In addition, the bonding properties of the modified adhesives were evaluated by the tensile shear strength of the lap joints, and mould growth was visually inspected. The resulting modified protein-based adhesives demonstrated improved stability in high humidity environments. Enhancing the hygroscopic properties of protein-based fish adhesives has the potential to unlock new opportunities and applications, providing a healthier and more environmentally sustainable alternative to petroleum-based adhesives.
Ključne besede: protein‐based adhesive, polymer stabilization, hygroscopicity, fish adhesive modification, fish industry waste, circular economy, bonding properties
Objavljeno v DiRROS: 12.08.2024; Ogledov: 1183; Prenosov: 828
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Povzetek: On 6th May 2018 a juvenile specimen of ribbon fish (Trachipterus trachypterus) was collected in shallow waters in Izola (Slovenia, northern Adriatic Sea). It measured 403 mm in total length and weighed 37.1 g. In stomach, fragments of seagrasses, pollen cones of pine, petals of terrestrial plant, fragments of terrestrial grass and beetles were found among food remains. The possible causes of this finding in Slovenian waters could be attributed to the ingression of southern Adriatic waters in its northern part. The specimen studied in this paper is the fifth record of this species in the Slovenian part of the Adriatic Sea. The cooperation between ichthyologists and fishermen proved to be crucial for the detection of the ribbon fish and other rare and less-known fish species, as well.
Ključne besede: ribbon fish, occurrence (biology), diet, Adriatic Sea
Objavljeno v DiRROS: 07.08.2024; Ogledov: 1012; Prenosov: 692
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Povzetek: The northern Adriatic Sea is well known for mercury (Hg) contamination mainly due to historical Hg mining which took place in Idrija (Slovenia). The formation of dissolved gaseous mercury (DGM) and its subsequent volatilisation can reduce the amount of Hg available in the water column. In this work, the diurnal patterns of both DGM production and gaseous elemental Hg (Hg0) fluxes at the water-air interface were seasonally evaluated in two selected environments within this area, a highly Hg-impacted, confined fish farm (VN: Val Noghera, Italy) and an open coastal zone less impacted by Hg inputs (PR: Bay of Piran, Slovenia). A floating flux chamber coupled with a real-time Hg0 analyser was used for flux estimation in parallel with DGM concentrations determination through in-field incubations. Substantial DGM production was observed at VN (range = 126.0–711.3 pg L−1) driven by both strong photoreduction and possibly dark biotic reduction, resulting in higher values in spring and summer and comparable concentrations throughout both day and night. Significantly lower DGM was observed at PR (range = 21.8–183.4 pg L−1). Surprisingly, comparable Hg0 fluxes were found at the two sites (range VN = 7.43–41.17 ng m−2 h−1, PR = 0–81.49 ng m−2 h−1), likely due to enhanced gaseous exchanges at PR thanks to high water turbulence and to the strong limitation of evasion at VN by water stagnation and expected high DGM oxidation in saltwater. Slight differences between the temporal variation of DGM and fluxes indicate that Hg evasion is more controlled by factors such as water temperature and mixing conditions than DGM concentrations alone. The relative low Hg losses through volatilisation at VN (2.4–4.6% of total Hg) further confirm that static conditions in saltwater environments negatively affect the ability of this process in reducing the amount of Hg retained in the water column, therefore potentially leading to a greater availability for methylation and trophic transfer.
Ključne besede: Idrija mercury mine, mercury evasion, fish farm, flux chamber, water-air exchange, Adriatic Sea, Idrijski rudnik živega srebra, ribogojnica, pretočna komora, izmenjava voda-zrak, Jadransko morje
Objavljeno v DiRROS: 12.07.2024; Ogledov: 1104; Prenosov: 608
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Povzetek: The authors studied the structure of the coastal fish assemblage in a temperate coral reef within a marine protected area in order to provide a baseline information on the occurrence and temporal distribution of fish and to highlight the importance of the coral reef to ichthyofauna. The coastal fish assemblage was investigated at two sites in Veliko jezero (Mljet National Park) in the southern Adriatic Sea with a non-destructive SCUBA visual technique in the period from 2013 to 2021. Altogether, 38 fish taxa were recorded on the right bank (coral reef) and 36 species on the left bank. The presence of the coral reef at a depth range between 9 m to 12 m is the main factor differentiating the fish fauna in these two areas, which are otherwise governed by the same environmental factors. At the coral reef a decrease in fish diversity was discovered with a steady regression from 2013 to 2021.
Ključne besede: fish fauna, spatial heterogeneity, Mediterranean coral reef, Cladocora caespitosa, marine protected area, Veliko jezero
Objavljeno v DiRROS: 10.05.2024; Ogledov: 1115; Prenosov: 786
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