Volume 51 (2022): Issue 1 (March 2022)

Parasites of the invasive Chinese sleeper (Perccottus glenii) were studied in five different localities at the site of the first introduction of the Carpathian population of this fish. We recorded eight taxa of parasites in Lviv water bodies. The monogenean Gyrodactylus perccotti and the cestode Nippoteania perccotti were recorded in all five lakes studied. These parasites represent Far East species introduced together with their host. Also the copepod Neoergasilus japonicus is a Far East parasite introduced to Europe with its aquaculture vector. Differences between the surveyed bodies of water were mainly related to their local seasonal conditions and watershed characteristics. The current data confirm the presence of co-introduced populations of G. perccotti and N. perccotti, which probably affects the future invasiveness of their host. Due to low acquisition of local parasites, we cannot confirm any significant effect of invasive fish on local parasite assemblages in this region. However, the presence of the non-indigenous copepod, N. japonicus, requires additional attention in the future.

In this study, three polymer types of microplastics (MPs), polyethylene (PE), polystyrene (PS) and polypropylene (PP), were exposed for 60 days in Xincun Bay (Hainan, China), a long-term mariculture tropical lagoon. High-throughput sequencing and scanning electron microscopy (SEM) were used to investigate the succession of microbial community structure and function on MPs after 10, 30, and 60 days of exposure, respectively. The results showed that diversity indices for bacteria from MPs were higher than those for bacteria from seawater. Significant differences were observed in community structure and metabolic function between MPs and seawater. The microbial network structure on MPs was more complex and dispersed than that in seawater. No significant differences in bacterial community structure and metabolic function were observed among different types of MPs. The biofilm on PS was the thickest, and the network structure on PP was the most complex one. With increasing exposure time, the biofilm attached to the surface of MPs became thicker and microbial composition showed some differences. The analysis of potential degradation bacteria and pathogens with abundance above 0.01% showed that the abundance of several potential plastic biodegraders on MPs was higher than that in seawater, while no potential pathogen was found enriched on MPs.

Cocconeis dapalistriata, first described as a member of the genus Cocconeis, is re-examined due to its unique ultrastructure. Both valvocopulae of this taxon show significant differences compared to those found in the genus Cocconeis. They are expanded and show some similarities with those found in Amphicocconeis. On the other hand, terminal parts of the raphe valve (RV) in C. dapalistriata are simple and the raphe valve (RV) striae are composed of small round areolae with a hymenate occlusion with radial slits, similar to those observed in Cocconeis. Campyloneis and Xenococconeis also have expanded valvocopulae but with numerous morphological differences compared to those found in C. dapalistriata. Furthermore, the areolae of the sternum valve (SV) in C. dapalistriata are occluded by a concave velum with no apparent internal slits, and externally ornamented with irregular silica crystals. Upsilococconeis Riaux-Gobin, Witkowski & Risjani gen. nov. is proposed to accommodate the latter taxon. First described from the Western Indian Ocean (Mascarenes), it was subsequently listed from the Western Pacific Ocean (Guam), the South Pacific Ocean (French Polynesia and New Caledonia) and from the Eastern Indian Ocean (Indonesia), and thus may qualify as pantropical.

Gökova Bay MPAs (southern Aegean Sea, Turkey) include six different no-take zones (NTZs: Akyaka, Çamlı, Akbük, Boncuk-Karaca, İngiliz Limanı, Bördübet), in four of which shore angling is permitted (Akyaka, Çamlı, Akbük, Boncuk-Karaca). This study determined the total catch and size of fish caught in the Akyaka MPA during recreational fishing. In total, fish representing 22 species belonging to 10 families were caught and most of them were smaller than their length at first maturity. The projection showed that the total catch weight reached significant values for recreational angling in the Akyaka MPA. The results of this study indicate that recreational angling may pose a threat to both MPAs and no-take zones, causing them to deviate from their primary conservation goal due to the harvesting of juveniles by recreational anglers.

The efficiency of ammonium nitrogen (N-NH₄⁺) and phosphate (P-PO₄³⁻) removal from wastewater with different loads of these nutrients was evaluated using Chlamydomonas reinhardtii (Chlorophyta) and Oscillatoria neglecta (Cyanophyta/Cyanoprokaryota). In addition, functional characteristics of the microalgae under the studied conditions were determined. It was demonstrated that Ch. reinhardtii is resistant to a wide range of concentrations of inorganic nitrogen and phosphorus compounds. Microalgae actively participate in the removal of N-NH₄⁺ from wastewater (removal efficiency of 49–63%, depending on the initial concentration). At the same time, Ch. reinhardtii showed low levels of P-PO₄³⁻ removal (7–18%) from the aquatic environment. O. neglecta, unlike Ch. reinhardtii, is sensitive to excessively high concentrations of N-NH₄⁺ (90–140 mg l⁻¹) and P-PO₄³⁻ (26–90 mg l⁻¹). However, it is characterized by high removal efficiency for both forms of nitrogen (60–61%) and phosphorus (43–55%) at their initial concentrations of 30–50 mg l⁻¹ and 7–14 mg l⁻¹, respectively. Therefore, O. neglecta is best suited for use in wastewater post-treatment.

In the Baltic Sea, where osmotic stress limits the growth of marine organisms, mariculture is driven primarily by the need to improve the status of the environment. To this end, several mussel farms have been attempted in selected areas, except the southern Baltic. The pilot culture of Mytilus trossulus was carried out with the use of a modified long-line system in the Gulf of Gdańsk in 2009–2012, providing the first evaluation of the mussel farming potential in this area. The growth rate of mussels (3.0–6.7 mm year⁻¹) in the gulf was in the low range, but the mean wet biomass gain (1.50 kg m⁻¹ normalized culture rope) was among the highest in the Baltic. After a two-year growth period, one tonne of mussels fixed in their soft tissues from 93 to 98 kg N t⁻¹ and 11 kg P t⁻¹. The cost-benefit analysis revealed a negative budget balance of production for human consumption, with a total income covering only 12.0% of the cumulative costs. Mussel farming in the gulf can therefore only be justified to improve the environmental quality if additional funding mechanisms are put in place to support farming activity.

As a major component of freshwater ecosystems, insect species play an important role in nutrient cycling and are often used as bioindicators of water pollution. Although extensive studies have characterized insects from freshwater habitats, little is known about the distribution of these species along the Lower Sector of the Danube River. Therefore, this survey conducted in the Danube section within the Romanian territory aimed to identify insect larvae belonging to seven different species of Odonata, Trichoptera, Ephemeroptera, Lepidoptera and Megaloptera by DNA barcoding and to investigate their distribution, density and frequency. A total of 41 quantitative macrozoobenthic samples were collected during two consecutive years (2019 and 2020). Species showed large differences in the distribution and density along different sections, and an overall tendency to populate downstream areas, except for Sialis morio. On the other hand, only Hydropsyche bulgaromanorum, Triaenodes bicolor and S. morio larvae were identified in the upstream section (Sulina branch). These data provide baseline information on the larger range of some of the most common aquatic insects in the Romanian Danube section in relation to several environmental parameters based on the first molecular identification of these species using COI gene sequencing.

Since the 1990s, anthropogenic activities have been the major direct or indirect threats to the structural and functional organization of the unique ecosystem of the Caspian Sea (CS). This study attempts to investigate the relationships between fish community structure and environmental parameters and to analyze the Abundance Biomass Comparison (ABC) in the CS. The input data, including catch data by species and environmental parameters, were collected from 1996 to 2017. Of the 13 bony fish species identified, only two species Rutilus kutum and Chelon aurata accounted for 47.14% and 62.65%, and 40.80% and 29.34% of CPUE and NPUE, respectively. DisTLM revealed that five environmental variables showed a significant linear relationship with the NPUE resemblance matrix. Based on the AIC criteria, the combination of year, precipitation, SST_Apr, SSL, SST, GTA, Iranian rivers, and Volga discharges explain 80.3% of the total variability. Based on the ABC curves and W statistics, it was concluded that the fish assemblage was environmentally stressed from 1996 to 2003. The Shannon diversity index (H′) showed a decreasing trend, suggesting that fish species have been exposed to increasing stress over the past 22 years. Considering the current environmental conditions (downward trend in SSL river discharge and increase in SST) and anthropogenic activities, it appears that the downward trend will continue in the future.

Due to their unique biochemical composition, sea cucumbers are highly prized marine echinoderm species. One of their most important properties is that they contain a high amount of collagen in their body wall. In this study, the relationship between collagen and pepsin-solubilized collagen yields from Holothuria tubulosa and Holothuria poli and morphometric and biochemical parameters were investigated.

Collagen yields were in the range of 10.63–16.04% for H. tubulosa and 7.12–13.10% for H. poli. It was determined that they may be related to length, body wall weight, and biochemical composition at different length frequencies. Moreover, maturity may have a direct effect on the yield, as mature specimens were found to have lower content of collagen, whereas immature small specimens contained a higher percentage of collagen. It was found that with increasing pepsin concentration, the PSC yield increased to 1.83–1.89% in H. tubulosa and H. poli, respectively. It was determined that collagen from smaller individuals, which contained more moisture and ash, was likely more susceptible to pepsin hydrolyzation.

This is the first published study demonstrating that collagen yield of sea cucumbers can vary with length, weight, maturity, and biochemical composition, in addition to species-specific differences.

Unassessed fisheries, mostly non-targeted fisheries, are now particularly predominant in many commercial fisheries and are critical to food security in developing countries. These fisheries typically lack reliable data essential for assessing their stocks, leaving them susceptible to overfishing and declining yield over time. This study proposes a framework for determining the life history and management of such fisheries. Data on the length composition and reproduction of wahoo Acanthocybium solandri, a common bycatch species in commercial fisheries, were obtained from observers aboard Chinese longline vessels in the Eastern Atlantic between 2010 and 2020 and were used as a case study. A comprehensive methodological approach was applied using data on this species to estimate its life history parameters, to evaluate biological reference points, and to provide proxies for the stock status. The final main growth parameters obtained were: L_inf = 161.21 cm FL (157.34–194.68), K = 0.47/year (0.14–0.65); estimated size at first maturity was 89.6 cm FL. As assessed by the set of methods applied, the wahoo stock state was healthy in the Tropical Eastern Atlantic Ocean. This study advises against using a single approach to determining life history parameters in data-limited fisheries, as this may affect reference points and thus management recommendations. This study provides a route whereby many easy-to-apply methods can be used to understand the status of multiple stocks in poorly managed fisheries, and thus provide management plans.