The relative growth of walking legs of adult Chinese mitten crabs, Eriocheir sinensis in the Odra estuary (Poland). The major axis statistical modeling

Abstract We have quantified the relative growth of the merus and the propodus & carpus of walking legs of an adult of Eriocheir sinensis against the carapace width by fitting the major axis lines. Different lines have been fitted to data relative to male and female individuals. Slope and elevation tests have been performed to investigate sexual dimorphism. Isometry tests have been used to classify the relative growth of each part of the legs against the carapace width as isometric or allometric. All the slope tests have not rejected the null hypothesis of a common slope for the major axes fitted to male data and to female data. However, all the elevation tests have rejected the null hypothesis of a common elevation; so sexual dimorphism was detected for all measured leg parts. The isometry tests have rejected the null hypothesis of isometry only for the merus of the first (left and right) legs of male individuals. All the other isometry tests have not rejected the null hypothesis of isometry. So the relative growth of all the measured leg parts, but the merus of the first (left and right) legs of males, against the carapace width was isometric both for males and for females

Major axis approach to the statistical analysis of the relative growth of Chinese mitten crab (Eriocheir sinensis) in the Odra estuary (Poland)

Abstract A total of 379 individuals of Eriocheir sinensis (198 males and 181 females) were captured in the Odra estuary (Poland). The crabs were thawed and their carapace length (CL), the maximum carapace width (CW) and the maximum height (CH) were measured. Measurements were also taken on each claw, the claw length (CHL1, the right claw; CHL2, the left claw), the width (CHW1 and CHW2 for the right and the left claw, respectively), and the height (CHH1 and CHH2 for the right and the left claw). For each crab, the wet weight was measured for each of the following body components: the whole crab (CrWe), the carapace (CaWe), the right claw (WRC) and the left claw (WLC). For females, the relationship between CL and CW, CH and CW were isometric, and for all linear measures, the relationship with CW was positively allometric. For males only this first relationship was isometric, but others were positively allometric. The differences between relative growth parameters for males and females were statistically significant

The Effect of Maintenance Works on Ichthyofauna in the Context of Hydrochemical Conditions of Small Watercourses of Central and North-Western Poland

The studies were conducted in the summers of 2017 and 2018 on three watercourses in Central and North-Western Poland, the where maintenance works involving disposal of sediment and silt were performed in the autumn of 2017. Monitoring of the ichthyofauna in the Rurzyca River and the Tywa River before (year 2017) and after the maintenance works (year 2018) indicated a decrease in the number of species. Altogether, 23 fish species were caught in all the watercourses. Out of these, 12 species were not recorded after the studied rivers had been dredged. A slight decrease in the number of fish species was observed in each studied river after the maintenance works. The values of physicochemical parameters obtained for each watercourse indicate a low quality of the waters. After silt had been removed from the watercourses, lower N-NO3values were observed at most research sites, whereas the N-NH4+ values increased significantly (except for one site on the Kanał Habdziński). Additionally, high volumes of P-PO43-were observed (except for sites 2 and 3 on the Kanał Habdziński and site 2 on the Rurzyca River). Maintenance works performed on small watercourses have a negative impact on the quality of waters and a less significant impact on the number of fish and biodiversity. This appears to be connected with migration of fish in the river during the maintenance works and avoidance of the consequent unfavourable conditions to gradually return to their habitats afterwards

Condition and population structure of the round goby (Neogobius melanostomus Pallas, 1811) in Szczecin Lagoon in 2010–2014

The round goby (Neogobius melanostomus Pallas, 1811) is one of the most invasive fish species in the world, including Poland. 300 fish of this species were collected in the waters of Szczecin lagoon between 2010 and 2014 and examination of the size, sex and age structures of the population and of the condition of the fish was performed. Total length and standard length of all the collected fish amounted to 149.2 mm (±42.21) and 128.1 mm (±38.65), respectively. The age structure of the fish consisted of nine generations, with clear prevalence of the fish aged 3+ and 4+. Mean values of condition factors for the whole fish sample amounted to 0.20 (±0.02). However, no statistically significant differences in particular years were observed (ANOVA, p > 0.05), but the condition of the fish between 2010 and 2011 was slightly higher than between 2013 and 2014. The obtained results indicate that the Szczecin Lagoon environment provides this species with favourable living conditions and it can be stipulated that the quantity of individuals of this fish species will increase

An Assessment of Progress in the Implementation of the BWM Convention on Ships as an Important Element in Protecting Aquatic Ecosystems

The purpose of this study was to assess progress in the implementation of rules for the control and handling of ballast water and sediments, regulated by the International Convention on the Control and Handling of Ship Ballast Water and Sediments (BWM Convention). The survey was conducted in 2018-2019 among seafarers responsible for handling ballast tanks. Analysis of the survey data revealed that despite the introduction of water treatments, ballast water continues to be a vector for the transfer of non-native organisms. This is due to the low effectiveness of the methods used, and the fact that 8% of the respondents answered that no BWT systems were used on the ships they manage. Despite this, some seafarers (4.7%) indicated that increasing environmental awareness and adherence to BWM principles should result in improved protection of aquatic ecosystems. Therefore, the global problem concerning the transport of non-native organisms via ballast water has still not been solved effectively. In the near future, improved BWT systems should be introduced, which after proper training of the crew will act as a barrier to the transfer of non-native organisms in ballast water

A generalized, nonlinear regression approach to the length-weight relationship of European perch (Perca fluviatilis L.) from the Polish coast of the southern Baltic Sea

Length-weight relationships in fish are important tools in fisheries management. The aim of this study was to estimate the growth curve W=aLbfor European perch, Perca fluviatilis L., from the Polish coast of the southern Baltic Sea (ICES Subdivision 25). The data set comprised the total weights and total lengths of 827 specimens caught during the 2011-2013 period. The mean total length (TL) was 169.4 mm (range 100.0-310.0 mm), and the mean total weight was 83.9 g (range 11.3-553.2 g). First, a multiplicative error term and a linear regression approach to loglog-Transformed data was considered. The following estimated values for the parameters were obtained: A = exp(-12.5323), b=3.25, s=0.07862. This approach was not successful in solving the common heterogeneity problem of the length-weight data. A generalized nonlinear regression approach to the original data was more suitable in our case. The estimated model was W = 3.83×10-6×L3.238+ ϵ, with ϵ∼norm(0,0.0281×E[W|L]2×1.242). The estimated 95% confidence interval for b was (3.218, 3.259), and the growth was allometric. The perch from the coastal waters of the Baltic Sea (ICES Subdivision 25) was characterized by slightly better condition than that caught in inland waters and estuaries

Effect of Artificial Regime Shifts and Biotic Factors on the Intensity of Foraging of Planktivorous Fish

It is still to be confirmed whether global warming with its predicted elevated water temperature will cause an increase in predation and alter phenological and physiological processes leading to changes in the size of aquatic organisms. In an experimental system of water column stratification simulating a natural combination of field conditions, we created artificial abiotic factors that mimicked the natural environment, i.e., light intensity, oxygen conditions, and thermal stratification. Subsequently, we added biotic factors such as algae, Daphnia, and planktivorous fish. We studied the intensity of foraging of planktivorous fish on individuals of Daphnia per min in different conditions of biotic and abiotic gradients. We demonstrated a possible scenario involving the risk of elimination of large prey within macrocladocera communities by predatory pressure as a result of climate change. A higher intensity of foraging of planktivorous fish caused or increased the occurrence of larger groups of planktonic animals with a smaller body size. The mechanisms of a future scenario were discovered at a higher trophic level in the aquatic environment

A comparative analysis of two allochthonous populations of the Chinese mitten crab (<i>Eriocheir sinensis</i> H. Milne-Edwards, 1853) from the Szczecin Lagoon (NW Poland) and San Francisco Bay (US west coast)

Selected biological and morphometric characters of two populations of the non-indigenous Chinese mitten crab, one from the Szczecin Lagoon (SL) and the other from San Francisco Bay (SFB), both sampled in autumn, were analysed. The SL crabs showed a significantly higher individual weight,length and carapace width. Males accounted for 55% (87 individuals) of the 179 SL crabs, and 62.9% (90 individuals) of the SFB crabs. Statistical analysis of metric characters, expressed as a percentage of carapace width (X2), enabled four diagnostic charactersto be identified: abdomen width (X11), carapace height (X3), left claw length (X7) and carapace length (X1). These jointly explain 71.75% of the differences between the SL and SFB crabs and are indicative of the distinctness of the populations

First record of brown colouration of Atlantic cod (Gadus morhua, L.) from the North Sea

This paper reports the biological characterisation of a specimen of Atlantic cod (Gadus morhua L.) with a unique brown colour, which is the first fish of this species with such a colouration recorded from European waters. It was caught in the coastal zone of the North Sea in June 2011. This ‘brown’ cod fish weighed 1074.3 g and had an overall length of 422 mm

Analiza jakości wód wybranych małych cieków zlokalizowanych w zlewni rzek Odry i Wisły

An important source of contamination of inland waters is the content of nitrogen and phosphorus compounds, which in agricultural areas constitute a significant threat by getting into flowing waters. The runoff of mineral substances from areas with high intensification of agriculture contribut to increase of nutrient content in rivers, which often causes disturbances in water quality, with excess nutrients supporting the growth of phytoplankton (algae receipts) and macrophytes and associated with it loss of habitats and desirable plant and animal species. The small rivers play an important role in the water quality of large rivers. The purpose of this work is to assess the quality of water in small lowland rivers, which are tributaries of the Odra and Wisła rivers, with particular emphasis on the content of biogenic compounds (nitrogen and phosphorus forms). The study was carried out on 10 small rivers from the Odra river basin (Płonia, Myśla, Tywa, Rurzyca and Wardynka River), and the Wisła river basin (Habdziński Channel, Zielona, Czarna-Cedron, Kraska and Molnica River). The analyzed water samples in all rivers had increased content of reactive phosphorus, which allows to classify the waters into non-class waters. The highest exceedences were recorded in the Płonia River (on average 1.505 mg P-PO43-/L) in the Odra river basin, while in the in the Wisła basin the highest exceedances were recorded in the Molnica watercourse (average 2.023 mg P-PO43-/L). Also high concentrations of the nitrate-nitrogen content were recorded, and the highest amounts of N-NO3-/L were found in the Rurzyca River (the Odra catchment – 7.321 mg N-NO3-/L) and in Molnica River (Wisła catchment – 5.092 mg N-NO3- /L). Lower values of ammonium nitrogen were found in all tested watercourses, classifying water to the first class of water quality according to Minister of the Environment Regulation (21.07.2016r.). Only increased concentrations classifying the examined waters up to the 2nd water quality class were recorded in the Rurzyca river (Odra catchment - 0.350 mg N-NO3- /L average, and in the Habdziński Channel (Wisła catchment - 0.293 mg N-NO3- /L). Significant increases in the content of biogenic compounds classifying tested waters to the 2nd class and above, were also conducive to low values of oxygen concentration in water and high conductance. For example in the Molnica river, high nitrate nitrogen and phosphate content influenced on low water oxygenation. In addition, there was a very low water level in the watercourse, which could have triggered nutrient loads in bottom sediments. Contamination of waters from agricultural areas with nitrogen and phosphorus compounds may pose a threat to larger rivers to which they can pass without proper monitoring.Istotnym źródłem zanieczyszczenia wód śródlądowych są zawartości związków azotu i fosforu, które na obszarach rolniczych stanowią znaczące zagrożenie przedostając się do wód płynących. Do nadmiernego wzrostu zawartości związków biogennych w rzekach przyczyniają się spływy substancji mineralnych z terenów o dużej intensyfikacji rolnictwa, co niejednokrotnie jest przyczyną zaburzeń jakości wody, przy czym nadmiar składników odżywczych sprzyja wzrostowi fitoplanktonu (zakwitów glonów) i makrofitów oraz związanej z tym utraty siedlisk i pożądanych gatunków roślin i zwierząt. Dużą rolę w kształtowaniu jakości wody dużych rzek pełnią niewielkie dopływy stanowiące małe cieki wodne. Celem niniejszej pracy jest ocena jakości wód w wybranych małych nizinnych ciekach wodnych będących dopływami rzeki Odry i rzeki Wisły ze szczególnym uwzględnieniem zawartości związków biogennych (formy azotu i fosforu). Badaniami objęto 10 niewielkich cieków z obszaru zlewni rzeki Odry (rzeki: Płonia, Myśla, Tywa, Rurzyca i Wardynka), oraz zlewni rzeki Wisły (Kanał Habdziński, Zielona, Czarna-Cedron, Kraska i Molnica). Analizowane próby wody we wszystkich rzekach miały podwyższone zawartości fosforu fosforanowego, co pozwala zaklasyfikować badane wody do wód pozaklasowych. W zlewni rzeki Odry największe przekroczenia norm odnotowano w rzece Płonia (średnio 1.505 mg P-PO43-/L), natomiast w zlewni Wisły największe przekroczenia zanotowano w cieku Molnica (średnio 2.023 mg P-PO43-/L). Również wysokie stężenia odnotowano analizując wody pod kątem zawartości azotu azotanowego, a największe ilości N-NO3-stwierdzono w rzece Rurzyca (zlewnia Odry – 7.321 mg N-NO3-/L) i w Molnicy (zlewnia Wisły – 5.092 mg N-NO3-/L). We wszystkich badanych ciekach stwierdzono niższe ilości azotu amonowego, klasyfikując wody do I klasy czystości wg Rozp. MŚ z 21.07.2016r. Jedynie podwyższone stężenia klasyfikujące badane wody do 2 klasy czystości wód zanotowano w rzece Rurzyca (zlewnia Odry – średnio 0.350 mg N-NH4+/L, oraz w Kanale Habdzińskim (zlewnia Wisły – 0.293 mg N-NH4+/L). Znaczące podwyższenia zawartości związków biogennych klasyfikujące badane wody doII klasy i powyżej II klasy czystości wód sprzyjały również niskim wartościom stężenia tlenu w wodzie oraz wysoką konduktancją. Przykładem jest tu rzeka Molnica, w której wysokie zawartości azotu azotanowego oraz fosforanów przekładały się na niskie natlenienie wody i wysokie przewodnictwo właściwe. Ponadto w cieku była bardzo niski stan wód, co mogło uruchomić pokłady ładunków biogennych w osadach dennych. Zanieczyszczenia wód z terenów rolniczych związkami azotu i fosforu mogą stanowić zagrożenie dla większych rzek, do których bez odpowiedniego monitoringu mogą się przedostawać