Gonad maturity in female Chinese mitten crab Eriocheir sinensis from the southern Baltic Sea – the first description of ovigerous females and the embryo developmental stage

AbstractThis paper describes for the first time the gonad maturity stage of Eriocheir sinensis females (carapace width 55.20–78.10mm) collected in the autumns and winters of 2005–2012 in the Gulf of Gdańsk and Vistula Lagoon (southern Baltic Sea). Seventeen females had gonads in the penultimate stage, which indicates that spawning would shortly take place. Four other females had gonads in the last stage, which means they were already carrying eggs. These accounted, on average, for 17.9 ± 2.9% of female weight and were in the 3rd and 4th embryo developmental stage. The results show that the low salinity of southern Baltic Sea (≤ 7 PSU) permits mating and fertilization as well as embryo development in E. sinensis. It is still not clear, whether such a salinity level will enable hatching and the complete larval cycle

Epibiotic mites associated with the invasive Chinese mitten crab Eriocheir sinensis – new records of Halacaridae from Poland **This research was supported by grant No. N304 082 31/3219 from the Polish Ministry of Education and Science.

AbstractSeven epibiotic halacarid mites (Caspihalacarus hyrcanus, two species of Copidognathus, Halacarellus petiti, Porohalacarus alpinus, Soldanellonyx monardi and S. chappuisi), two oribatid mites (Hydrozetes lacustris and Trhypochthoniellus longisetus) and one water mite (Piona pusilla) were found on the setae-covered claws of eighteen Chinese mitten crabs (Eriocheir sinensis) collected from fresh and brackish waters in Poland and Germany. The most abundant of the 111 mite individuals recorded was one of the Copidognathus species (N=52); this was followed by H. petiti (N=38) and C. hyrcanus (N=13). This is the first record of H. petiti and of the genus Copidognathus from Polish waters. The possibility of migrating over long distances assisted by catadromous mitten crabs enhances mite dispersal, as well as their introduction to new environments

Exceptions and exemptions under the ballast water management convention – Sustainable alternatives for ballast water management?

Highlights • Data quality is very important for conducting a reliable risk assessment. • Same locations should be confined to smallest practicable areas within a port. • Nearly all shipping routes with adequate data resulted in high-risk outcomes. • Pelagic larval traits are key factors in natural dispersal modelling assessments.The International Convention for the Control and Management of Ships' Ballast Water and Sediments (BWM Convention) aims to mitigate the introduction risk of harmful aquatic organisms and pathogens (HAOP) via ships’ ballast water and sediments. The BWM Convention has set regulations for ships to utilise exceptions and exemptions from ballast water management under specific circumstances. This study evaluated local and regional case studies to provide clarity for situations, where ships could be excepted or exempted from ballast water management without risking recipient locations to new introductions of HAOP. Ships may be excepted from ballast water management if all ballasting operations are conducted in the same location (Regulation A-3.5 of the BWM Convention). The same location case study determined whether the entire Vuosaari harbour (Helsinki, Finland) should be considered as the same location based on salinity and composition of HAOP between the two harbour terminals. The Vuosaari harbour case study revealed mismatching occurrences of HAOP between the harbour terminals, supporting the recommendation that exceptions based on the same location concept should be limited to the smallest feasible areas within a harbour. The other case studies evaluated whether ballast water exemptions could be granted for ships using two existing risk assessment (RA) methods (Joint Harmonised Procedure [JHP] and Same Risk Area [SRA]), consistent with Regulation A-4 of the BWM Convention. The JHP method compares salinity and presence of target species (TS) between donor and recipient ports to indicate the introduction risk (high or low) attributed to transferring unmanaged ballast water. The SRA method uses a biophysical model to determine whether HAOP could naturally disperse between ports, regardless of their transportation in ballast water. The results of the JHP case study for the Baltic Sea and North-East Atlantic Ocean determined that over 97% of shipping routes within these regions resulted in a high-risk indication. The one route assessed in the Gulf of Maine, North America also resulted in a high-risk outcome. The SRA assessment resulted in an overall weak connectivity between all ports assessed within the Gulf of the St. Lawrence, indicating that a SRA-based exemption would not be appropriate for the entire study area. In summary, exceptions and exemptions should not be considered as common alternatives for ballast water management. The availability of recent and detailed species occurrence data was considered the most important factor to conduct a successful and reliable RA. SRA models should include biological factors that influence larval dispersal and recruitment potential (e.g., pelagic larval duration, settlement period) to provide a more realistic estimation of natural dispersal

The Effect of CO2-Induced Seawater Acidification on the Behaviour and Metabolic Rate of the Baltic Clam Macoma balthica

The aim of this study was to investigate the effect of CO2-induced seawater acidification (pH 8.1; control pH 7.0 and 6.0) on the survival, behaviour and metabolic rate of the Baltic clam Macoma balthica during short- (36 hours) and long-term (14 days) exposures. Total metabolic rate and gaping behaviour (shell opening and closing) were determined based on heat dissipation measurements using an isothermal twin calorimeter of the Calvet type. The survival and burrowing behaviour during long-term exposure were observed every day. Short-term exposure to reduced pH did not significantly affect the resting or active metabolic rate. Neither were there any significant changes in gaping behaviour. However, long-term exposure significantly affected burrowing behaviour. In the lowest-pH treatment, both resting and active metabolic rates were also significantly higher than in the control

Non-native crab <i>Rhithropanopeus harrisii</i> (Gould, 1984) - a new component of the benthic communities in the Gulf of Gdańsk (southern Baltic Sea

The aim of this study was to determine the occurrence, spatial distribution and abundance pattern of the Harris mud crab <i>Rhithropanopeus harrisii</i> in the Gulf of Gdańsk (southern Baltic Sea). Between 2006 and 2010, this species was found at 69 out of 129 sampling stations, at depths from 0 to 20 m. Two main aggregations of the Harris mud crab were established: (1) in Puck Bay (max. density 19 indiv. 100 m^-2) and (2) in the Gdynia and Sopot area (max. density 5 indiv. 100 m^-2). 920 specimens were collected during the whole sampling period: 150 juveniles, 370 females and 400 males. The minimum measured carapace width was 1.96 mm, the maximum 21.40 mm (mean 9.03 ±4.11 mm)

The invasive amphipod Gammarus tigrinus Sexton, 1939, in Puck Bay

The paper is a report on the occurrence of the species Gammarus tigrinus Sexton, 1939, in the coastal waters of Puck Bay

The Chinese mitten crab <i>Eriocheir sinensis</i> (Decapoda: Grapsidae) from Polish waters

The Chinese mitten crab Eriocheir sinensis Milne-Edwards, 1854 is a newcomer to the Baltic Sea. Previous studies have shown that since the 1940s single large specimens of this species have been caught annually in Polish waters. The invasion of the Chinese mitten crab has been reported from many European countries, including Poland, where it is especially abundant in the Odra Estuary. Of 186 specimens captured in Lake Dabie in August 1998, 45% were females and 55% males. The carapace width of these crabs varied between 53 and 88 mm and the average wet weight was 169 &#177; 45.3 g

New data on benthic Naididae (Annelida, Clitellata) in Polish brackish waters

This paper presents new findings on oligochaete species inhabiting Polish brackish waters. Identification of 455 specimens collected in September 2013 and July 2014 during the macrozoobenthos survey in the Port of Gdynia (the Gulf of Gdańsk, the southern Baltic Sea, Poland) showed the presence of six species belonging to two subfamilies Naidinae and Tubificinae

The combination of low salinity and low temperature can limit the colonisation success of the non-native bivalve Rangia cuneata in brackish Baltic waters

We studied the behavioural (burrowing and valves gaping) and metabolic responses of Atlantic rangia Rangia cuneata (G.B. Sowerby I, 1832) at different salinities and temperatures. Three salinities (S = 0.5, 7.0, 10.0) were tested at 20 °C, with an additional control of 2.4. The control salinity (S = 2.4) was also tested at 10 °C to examine responses specific to colder temperatures. Clams exposed to the lowest (S = 0.5, T = 20 °C) and the highest salinity (S = 10.0, T = 20 °C), as well as lower temperature (T = 10 °C, S = 2.4) significantly (p .05). Clams kept their shells open in the lowest salinity, but closed in the highest salinity and at lower temperature. The closure time was longer in salinity of 10.0 than at temperature of 10 °C, where the highest reduction in the metabolic rate occurred in relation to the control conditions. This latter fact, in combination with shell closure, may indicate the activation of an anaerobic pathway. Thus, in the long term, lower temperatures may adversely affect R. cuneata, especially at very low salinity (S = 0.5, 2.4), in which this hyper-osmoregulating species has to strongly pump water with ions and oxygen to compensate for energy demand. In salinity of 10.0, where the species is isosmotic to the environment, changes in behaviour (moving to the sediment surface and closing the shell) with a simultaneous reduction in the metabolic rate may be due to lower costs of osmoregulation. Our results may help explain the strong inter-annual fluctuations in the population size of this subtropical species in the Baltic coastal waters resulting from the mass mortality of adults after long winters

Impact of Chinese mitten crab Eriocheir sinensis on blue mussel Mytilus edulis trossulus – laboratory studies of claw strength, handling behavior, consumption rate, and size selective predation

We examined the claw strength, handling behavior, consumption rate, and size selective predation of the invasive Chinese mitten crab Eriocheir sinensis feeding on native Baltic Sea blue mussels Mytilus edulis trossulus during 24 h laboratory experiments. Single starved crabs were offered 15 mussels (five mussels in three length classes) at a time. The total number of mussels consumed by a single crab increased significantly (P < 0.05) with the experimental time from 1.7 ± 0.7 # mussels crab−1 h−1 after 4 h to 0.2 ± 0.7 # mussels crab−1 h−1 after 24 h. The highest consumption rate was observed within the first 4 h, and it decreased significantly (P < 0.05) during the experiment. This was most likely due to the crabs being starved before the start of the experiment. E. sinensis can also harm blue mussel shells by crushing them without further consumption. The mean daily damage, and not consumption, by a single crab was 0.9 ± 1.4 of 11–40 mm mussels. The claw strength of E. sinensis ranged from 1.50 to 20.43 N (mean 8.51 ± 5.93 N) and was significantly correlated (P < 0.05) with sex and both claw size and carapace size. The study showed that E. sinensis may be able to impact the native M. edulis trossulus population abundance in the coastal Baltic waters either through direct predation or indirect mortality by damaging (crushing) the shell