Krzysztof Skóra

The Round Goby, Neogobius melanostomus, a Fish Invader on both sides of the Atlantic Ocean

During the past decade, a bottom-dwelling, aggressive, multiple-spawning fish, the round goby (Gobiidae: Neogobius melanostomus), has spread from its native region in the Ponto-Caspian throughout Europe and to the Laurentian Great Lakes in North America. An international workshop, held at the Hel Marine Station, Poland, was organized to summarize population features of the round goby. Common fish predators of round gobies in the Great Lakes and in native regions are obligate and facultative benthic fishes and occasionally, pelagic fishes. In contrast, the main predator of the round goby in the Gulf of Gdansk is the Great Cormorant (Phalacrocorax carbo). In the Great Lakes, round gobies have lead to the decline of mottled sculpin (Cottus bairdi) and logperch (Percina caprodes) and reduced the hatching success of native fishes by feeding on their eggs. In the Gulf of Gdansk, round gobies have increased in abundance, while three-spined sticklebacks (Gasterosteus aculeatus) have declined. Round gobies have a broad diet throughout their range; larger specimens are molluscivores. There are fewer species of parasites and lower infection rates of round gobies in recently colonized areas than in native areas. Overall, newly colonized round gobies in brackish waters and lakes are smaller, mature earlier, have a male biased operational sex ratio and are more short-lived compared with round gobies from marine (native) habitats.

Spread of alien (non-indigenous) fish species Neogobius melanostomus in the Gulf of Gdansk (south Baltic)

The round goby (Neogobius melanostomus) was first noticed in the Gulf of Gdansk in 1990. This Ponto-Caspian fish was most likely introduced to the Baltic environment from ships’ ballast water. During the first years of invasion, slow population growth was observed in the initially colonized regions. From 1994, round goby gradually spread in all shallow water zones of the Gulf of Gdansk. The area occupied by the population and the number of fish grew rapidly. By the end of the nineties, round goby became a dominant fish in shallow waters of the western part of the Gulf of Gdansk, where the fish used all solid substrates on the bottom, including concrete piers, big stones or even dumped waste for spawning and refuge. The presence of round goby in the Vistula Lagoon and shallow waters near Rugia (Western Baltic) was noticed for the first time in 1999. The present state, size and condition of the round goby population in the Gulf of Gdansk led us to predict a continual spread of this species into new regions of the Baltic. In addition, the population of round goby is so large that the species has started playing a part in commercial fishing in the Gulf of Gdansk.

Observations on Diet Composition of Neogobius melanostomus Pallas 1811 (Gobiidae, Pisces) in the Gulf of Gdansk (Baltic Sea)

This study documents the diet of Neogobius melanostomus (round goby) from three different habitats within the Gulf of Gdansk. Diet composition of the round goby in the Gulf of Gdansk appears similar to that in its natural environment within the Ponto-Caspian Basin. In its native habitat, the round goby feeds mainly on epibenthic organisms and opportunistically forages on seasonally abundant components of the benthic community. A natural mollusk-feeder, the round goby feeds mainly on the mussel Mytilus trossulus in the Gulf of Gdansk. This food preference most likely is due to the fact that M. trossulus is commonly distributed throughout most of the gulf and dominates the benthic biomass. The adult round goby prefers an environment full of hiding places that also can be used for nests. Thus, submerged stones or concrete structures covered with colonies of M. trossulus are its preferred habitat. Younger gobies are more abundant in the frontal areas of underwater concrete structures where the substrate is characterized by loose stones and the presence of Mya arenaria. These habitats have different faunal structures and, therefore, different trophic relations. The round goby, which is well suited for ecological expansion, has great potential to dominate the majority of the coastal zone of the Baltic Sea. Puck Lagoon, devoid of predatory fish and rich in mussel beds, is an ideal habitat for this gobiid species.

Metazoa parasites of the invasive round goby Apollonia melanostoma (Neogobius melanostomus) (Pallas) (Gobiidae: Osteichthyes) in the Gulf of Gdańsk, Baltic Sea, Poland: a comparison with the Black Sea

The known metazoa parasite fauna of the invasive round goby Apollonia melanostoma (formerly Neogobius melanostomus) consists of 12 species. The core of the parasite fauna comprises two species: Cryptocotyle concavum and Diplostomum spathaceum; secondary species are absent; satellite species include Cercariae gen. sp. and Ergasilus sieboldi; rare species are Acanthocephalus lucii, Anguillicola crassus, Bothriocephalus sp., Dichelyne minutus, Hysterothylacium aduncum, Pomphorhynchus laevis, Piscicola geometra, and Tylodelphys clavata. Fifty percent of metazoa parasites that occurred in the invasive round goby in the Gulf of Gdańsk (an invasion that was first detected in 1990) are also typically found in the native Gulf of Gdańsk gobiids. The round goby hosts common fish parasite species: C. concavum and D. minutus, but none that are unique to the species and no Ponto–Caspian parasites. Notably, the parasite species of the invasive round goby in the Gulf of Gdańsk includes species that are atypical for this species in its native habitat. In its new habitat, the round goby variously serves the roles of definitive, second intermediate, and paratenic host for different parasite species. The fish species is involved in a parasitic system that includes fish-eating birds, fishes of different ecological groups (predatory, planktivorous, and benthivorous), and invertebrates.

Congener-specific data on polychlorinated biphenyls in tissues of common porpoise from Puck Bay, Baltic Sea

Individual congeners of polychlorinated biphenyls (PCBs), including the highly toxic non-ortho coplanar 3,3′,4,4′-tetrachlorobiphenyl (IUPAC No. 77), 3,3′,4,4′,5-pentachlorobiphenyl (IUPAC No. 126), and 3,3′,4,4′,5,5′-hexachlorobiphenyl (IUPAC No. 169), and their mono- and di-ortho analogs, have been identified and quantified in the blubber, liver, and muscles of three female common porpoise Phocoena phocoena collected from the Puck Bay (inner Gulf of Gdańsk, Poland) in 1989–1990, to elucidate actual concentrations and toxic potential. The total 2,3,7,8-tetrachlorodibenzo-p-dioxin toxic equivalent for 13 coplanar PCBs in blubber was 1,500±470 pg/g wet wt. 2,3′,4,4′,5-Pentachlorobiphenyl (IUPAC No. 118) was the most contributing individual and occupied between 57 and 67% in total toxic equivalent of coplanar PCBs in blubber, while 2,2′,4,4′,5,5′-hexachlorobiphenyl (IUPAC No. 153), 2,3,3′,4,4′-pentachlorobiphenyl (IUPAC No. 105) and 2,2′,3,4,4′,5′-hexachlorobiphenyl (IUPAC No. 138) comprised between 9.5–14, 7.6–11.5, and 7.2–11.0%, respectively (totally 82–95%), and 2,3,3′,4,4′,5-hexachlorobiphenyl (IUPAC No. 156) was absent. A potentially most toxic non-ortho PCB members such as 3,3′,4,4′,5-pentachlorobiphenyl, 3,3′,4,4′,5,5′-hexachlorobiphenyl and 3,3′,4,4′-tetrachlorobiphenyl were only minor contributors, altogether occupying between 1.0 and 14.5% in total TEQ of coplanar PCBs. Concentrations of total PCBs in lipids of the blubber ranged from 26 to 47 μg/g and were comparable or lower than reported earlier for common porpoises from the Baltic Sea, North Sea, and North Atlantic by other authors.

Mitochondrial Control Region and microsatellite analyses on harbour porpoise (Phocoena phocoena) unravel population differentiation in the Baltic Sea and adjacent waters

The population status of the harbour porpoise (Phocoena phocoena) in the Baltic area has been a continuous matter of debate. Here we present the by far most comprehensive genetic population structure assessment to date for this region, both with regard to geographic coverage and sample size: 497 porpoise samples from North Sea, Skagerrak, Kattegat, Belt Sea, and Inner Baltic Sea were sequenced at the mitochondrial Control Region and 305 of these specimens were typed at 15 polymorphic microsatellite loci. Samples were stratified according to sample type (stranding vs. by-caught), sex, and season (breeding vs. non-breeding season). Our data provide ample evidence for a population split between the Skagerrak and the Belt Sea, with a transition zone in the Kattegat area. Among other measures, this was particularly visible in significant frequency shifts of the most abundant mitochondrial haplotypes. A particular haplotype almost absent in the North Sea was the most abundant in Belt Sea and Inner Baltic Sea. Microsatellites yielded a similar pattern (i.e., turnover in occurrence of clusters identified by STRUCTURE). Moreover, a highly significant association between microsatellite assignment and unlinked mitochondrial haplotypes further indicates a split between North Sea and Baltic porpoises. For the Inner Baltic Sea, we consistently recovered a small, but significant separation from the Belt Sea population. Despite recent arguments that separation should exceed a predefined threshold before populations shall be managed separately, we argue in favour of precautionary acknowledging the Inner Baltic porpoises as a separate management unit, which should receive particular attention, as it is threatened by various factors, in particular local fishery measures.

Fish of Admiralty Bay (King George Island, South Shetland Islands, Antarctica)

SummaryThe species composition of the ichthyofauna of Admiralty Bay, King George Island was determined from results of sampling using bottom trawls, gill-nets and long-lines. Thirty-five species from 24 genera and 10 families (Table 1) were found. The number of species increased with depth (e.g. 7 species at 100 m, 14 species at 255 m and 21 species at 540 m), a tendency characteristic of Antarctic waters. In the bay, the catch rate obtained with a bottom trawl (greater than 30 kg/h) was roughly ten times lower than the catch rate using the same gear on the shelf around the Island. Notothenia gibberifrons was the dominant species in all trawls. The majority of these fish (about 95%) were immature juveniles (Table 4). Younger fish were found to inhabit shallower waters (Fig. 1). The majority of the fish of species Notothenia coriiceps neglecta, Notothenia rossii marmorata, Notothenia nudifrons, Trematomus newnesi and Trematomus bernacchii preferred waters about 255 m deep. Fourteen specimens of a previously undescribed species of the genus Psilodraco (currently being described by H. DeWitt) were caught in the bay within the 146 to 540 m depth range. The rare zoarcid, Lycenchelys aratrirostris, was also caught in Admirality Bay; previously this species had only been reported from the Elephant Island region. In the case of Trematomus newnesi, the occurrence of scales in the interorbital space was noted (Fig. 2), an observation which verifies this feature as a distinct taxonomical criterion for this species.

Bioaccumulation of selected trace elements in lung nematodes, Pseudalius inflexus, of harbor porpoise (Phocoena phocoena) in a Polish zone of the Baltic Sea

Concentrations of Cd, Pb, Cu, Zn, Cr, Co, Ni, Mn and Fe were determined by AAS in lung nematodes and their host organ of harbor porpoise in the Polish zone of the Baltic Sea. Correlation coefficients computed for all element pairs indicate significant co-associations between concentrations of Zn and Mn as well as Mn and Fe in P. inflexus and the host organ, and for the pair Cu-Cr in the parasite. Based on both concentration and discrimination factors it is well documented that the metals studied, especially Fe, Mn and Zn are bioaccumulated in P. inflexus with respect to the host lung, showing significant inter-specimen variations.

Toxic, essential and non-essential metals in harbour porpoises of the Polish Baltic Sea

Concentrations of Hg, Cd, Pb, Ag, Zn, Cu and Mn in liver, kidney, muscle, lung, heart and diaphragm of harbour porpoise (Phocoena phocoena) from the Polish Baltic Sea were determined. Distinct inter-tissue differentiation in metal concentrations was noted; liver showed maximum concentrations of Ag, Cu and Mn; kidney had the greatest concentrations of Cd and Pb while diaphragm contained most Zn. Muscle was generally characterized by small concentrations of all the metals analyzed. The concentrations of Zn, Cu, Hg and Cd in the liver, kidney and muscle found in our study are generally comparable with those reported for individuals of the same species inhabiting other geographical regions such as British, German and Danish waters. An order of magnitude smaller levels of hepatic and renal Cd in these mammals inhabiting NW European area compared to the West Greenland population were found while the Hg levels were about the same. This suggests low rates of Cd exposure, through an alimentary route, for harbour porpoise from the temperate marine areas.

Spatially Explicit Analysis of Genome-Wide SNPs Detects Subtle Population Structure in a Mobile Marine Mammal, the Harbor Porpoise.

The population structure of the highly mobile marine mammal, the harbor porpoise (Phocoena phocoena), in the Atlantic shelf waters follows a pattern of significant isolation-by-distance. The population structure of harbor porpoises from the Baltic Sea, which is connected with the North Sea through a series of basins separated by shallow underwater ridges, however, is more complex. Here, we investigated the population differentiation of harbor porpoises in European Seas with a special focus on the Baltic Sea and adjacent waters, using a population genomics approach. We used 2872 single nucleotide polymorphisms (SNPs), derived from double digest restriction-site associated DNA sequencing (ddRAD-seq), as well as 13 microsatellite loci and mitochondrial haplotypes for the same set of individuals. Spatial principal components analysis (sPCA), and Bayesian clustering on a subset of SNPs suggest three main groupings at the level of all studied regions: the Black Sea, the North Atlantic, and the Baltic Sea. Furthermore, we observed a distinct separation of the North Sea harbor porpoises from the Baltic Sea populations, and identified splits between porpoise populations within the Baltic Sea. We observed a notable distinction between the Belt Sea and the Inner Baltic Sea sub-regions. Improved delineation of harbor porpoise population assignments for the Baltic based on genomic evidence is important for conservation management of this endangered cetacean in threatened habitats, particularly in the Baltic Sea proper. In addition, we show that SNPs outperform microsatellite markers and demonstrate the utility of RAD-tags from a relatively small, opportunistically sampled cetacean sample set for population diversity and divergence analysis.