Przemysław Czerniejewski

Changes in condition and in carapace length and width of the Chinese mitten crab (Eriocheir sinensis H. Milne Edwards, 1853) harvested in the Odra River estuary in 1999-2007.

Changes in condition and in carapace length and width of the Chinese mitten crab (Eriocheir sinensis H. Milne Edwards, 1853) harvested in the Odra River estuary in 1999-2007 Carapace length and width as well as condition were analysed in 2336 Chinese mitten crabs, Eriocheir sinensis, caught in 1999-2007 in the Odra River estuary (Poland). Their condition was assessed using the Fulton coefficient and the carapace width-individual weight relationship. September through November catches netted the highest number of crabs (83.60% of the total sample); males accounted for 53.56% of the crabs caught at that time. Males showed a significantly higher mean individual weight, significantly higher carapace width and length, and a higher Fulton coefficient than the females. The lowest mean individual weight, carapace width and length, and the highest condition coefficients were recorded in those crabs caught in 1999-2000. Later on, the mean carapace width and individual weight increased, and the increase was accompanied by a reduction in condition of the crabs. Causes of the differences are being sought in environmental changes taking place in the Odra estuary.

Fecundity Of Vendace, Coregonus Albula (L.), From Several Lakes In Western Pomerania

Fecundity Of Vendace, Coregonus Albula (L.), From Several Lakes In Western Pomerania The aim of the study was to determine individual absolute and relative fecundity in vendace, Coregonus albula (L.), populations from four Western Pomeranian lakes that differ morphometrically and trophically. The highest mean total length and individual weight were recorded in the fish from the mesotrophic lakes Ińsko (229.1 mm and 106.6 g, respectively) and Miedwie (228.1 mm and 105.1 g, respectively). The highest individual absolute fecundity in particular age groups as well as individual relative fecundity were noted in the fish from Lake Miedwie (6635-24620 eggs per female and 10756-11609 eggs per 100 g female body weight, respectively), while the lowest values of these parameters were confirmed in fish from Lake Glinna (4782-6087 eggs per female and 6406-6953 eggs per 100 g female body weight). A high, statistically significant correlation between absolute fecundity and total fish length and a slightly lower correlation between absolute fecundity and fish age were noted in all of the populations studied. Płodność Sielawy, Coregonus Albula (L.) Z Kilku Jezior Pomorza Zachodniego Celem badań było oszacowanie płodności osobniczej bezwzględnej i względnej populacji sielaw pozyskanych z 4 zachodniopomorskich jezior (rys. 1, tab. 1). Analizy wieku ryb wskazują, iż w połowach gospodarczych prowadzonych w jeziorach Miedwie, Ińsko i Woświn dominują ryby w wieku 2+, a w jeziorze Glinna w wieku 3+ (tab. 2). Największą średnią długością całkowitą i masą jednostkową charakteryzowały się ryby z mezotroficznych jezior Ińsko (odpowiednio 229,1 mm i 106,6 g) i Miedwie (odpowiednio 228,1 mm i 105,1 g). Analiza płodności osobniczej bezwzględnej i względnej wykazała, iż ryby z jeziora Miedwie charakteryzują się najwyższymi wartościami tych parametrów (odpowiednio: 6,64-24,62 x 103 ziaren ikry/samicę oraz 10,76-11,61 x 103 ziaren ikry na 100 g masy ciała samicy), natomiast najniższymi z eutroficznego jeziora Glinna (odpowiednio 4,78-6,09 x 103 ziaren ikry/samicę oraz 6,41-6,95 ziaren ikry na 100 g masy ciała samicy) (tab. 3). Zaobserwowano wzrost płodności bezwzględnej sielawy w miarę zwiększania się długości ciała (tab. 4) i wieku ryb (tab. 5). Wyniki analizy regresji wskazują, iż płodność osobnicza bezwzględna jest lepiej zdeterminowana rozmiarami ciała niż wiekiem ryb. Nie stwierdzono istotnych relacji pomiędzy płodnością osobnicza bezwzględną sielawy a geograficznym położeniem jezior na terenie Polski (rys. 2, tab. 6).

Seasonal Changes in Condition Factor and Weight-Length Relationship of Invasive Carassius gibelio (Bloch, 1782) from Leszczynskie Lakeland, Poland

Samples of invasive cyprinid fish, the Prussian carp (Carassius gibelio), were collected by fyke nets in Leszczynskie Lakeland (Poland) during the summer and autumn, 2010, and during the spring, 2011. All captured fish were females. For each fish, the total weight () and the standard length () were measured and Fulton’s condition factor was computed. Graphical investigation and the Mann-Whitney-Wilcoxon test showed statistically significant location shift of the distribution from summer to autumn (upward) and from autumn to spring (downward). Relationship between total weight and standard length was described with the mean growth curve . Seasonal parameters ( and ) were estimated with a nonlinear regression approach, that is, numerical optimization methods. Growth was allometric in summer and autumn and isometric in spring. The differences between summer and autumn growth curves and between autumn and spring growth curves were statistically significant. The seasonality exhibited by the condition factor and the growth curve may be due to different spawning, breeding, and feeding activity in the different seasons and to variable environmental conditions.

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

Abstract Length-weight relationships in fish are important tools in fisheries management. The aim of this study was to estimate the growth curve W=aLb for 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.