Growth pattern of flounder, Platichthys flesus (L.), from the Gulf of Gdańsk (southern Baltic Sea)

Background. It is a common perception that growth rates of many commercially-exploited fish species have been well known. It is evident, however, that in certain cases, especially in brackish water environments those growth rates may be diversified. Therefore, determination of growth patterns of various stocks of the same fish, living in different salinity regimes may be important for efficient fisheries management, especially fish-quotas negotiations. The aim of the presently reported study was to estimate the growth rates of length and weight of flounder Platichthys flesus (L.) from the Gulf of Gdańsk and to compare them with those from the Pomeranian Bay and Słupsk Furrow areas. Materials and methods. A total of 200 fish, collected in the coastal waters of Hel in 1997, was analysed. The fish were caught using flatfish gill nets. The age of flounder was determined from otoliths, whereas measurements of the annual ring increments were made using a dissecting microscope with reflected light over a dark background. The microscope was outfitted with a camera and linked to computer. The images were processed using an image-processing software “Multiscan”. The method of Vovk was employed to study the growth rate of flounder, both for the whole sample and in relation to both sexes. The calculation of the growth rates of length and weight were aided by the equations of von Bertalanffy. Results. The total length of the flounder studied ranged from 4.3 to 46.0 cm for ages from one through ten. The mean length reached 23.7 cm, while the mean age was 4.6 years. The prevalent age classes were III, IV, and V. The growth rates of length were different in males and females. Until the third year of life males grew slightly faster, while from the fourth year, the females grew more rapidly. The von Bertalanffy equations that describe theoretical growth (length and weight) of flounder, from the Gulf of Gdańsk were calculated. Conclusion. The differences found in the morphometric and biological characters between the samples collected in three different locations of the southern Baltic (Pomeranian Bay, Słupsk Furrow, and Gulf of Gdańsk) may indicate that they represent separate stocks (populations)

Biometric characters of the blue bream Abramis ballerus (L.) (Cyprinidae) from Lake D±bie

The paper presents results of study on 24 metric characters and 19 meristic ones, performed on 50 specimens of the blue bream collected in Lake D±bie. With the aid of Cochran and Cox test the results obtained were compared with the data concerning the population from the river Dnepr

Occurrence of Eimaria protozoa in lambs in Western Pomerania, Poland

A total of 250 Merino lambs from the Lubuskie province and 83 Suffolk lambs from the Zachodniopomorskie province were examined. The level of infection with Eimeria protozoa was determined on coproscopic examinations using the Willis-Schlaaf flotation method. The species composition of the coccidia was determined using Pellerdi’s system. The prevalence of lamb infection with coccidia averaged 85.18% in the Zachodniopomorskie province and 55.32% in the Lubuskie province. Coproscopic examinations showed that the animals were infected with different species. Eight species were isolated from faecal samples: E. faurei, E. ovinoidalis, E. pallida, E. intricata, E. parva, E. arloingi, E. ninakohlyakimovae and E. granulosa. E. parva (53%) and E. ninakohlyakimovae (47.8%) were the dominant in the Zachodniopomorskie province, and E. ninakohlyakimovae (65%) and E. intricata (43.3%) in the Lubuskie province

Meristic and morphometric characters of small sandeel, Ammodytes tobianus L. (Actinopterygii: Ammodytidae), from the Gulf of Gdańsk, Baltic Sea

Background. The small sandeel, Ammodytes tobianus L., is a fish species of no commercial value, which is probably why its biology and, particularly, taxonomic status has not attracted much interest. However, the ecological importance of this species outweighs its economic value. It has been regarded a "vulnerable" fish species and therefore its taxonomic status urgently needs more detailed studies. The presently reported study was intended to be a contribution to the knowledge on poorly known morphology of this fish, from a single location in the southern Baltic Sea. Materials and methods. The fish (130 specimens, 9.2-16.3 cm TL) were collected in June 1995 from the area between the Puck Bay and open waters of the Gulf of Gdańsk, at the depth of 8 m. Taxonomic analysis involved both meristic and morphometric characters. The lengths were expressed as percentage of the standard length (SL) of the fish while the fish head characters-as percentage of the head length (HL). In addition, the coefficients of correlation and determination (r and r2, respectively) were calculated for the relations between all characters studied and standard length (SL) and for the relations between the characters pertinent to head and the head length (HL) in the sample examined. The fish age was determined from the otoliths. Results. The age of fish examined ranged from 1+ to 4+, and the sandeels aged 2+ were the distinctly dominant age group. The most abundant size group was the 13.0-13.99 cm length class. The coefficients of variation in the meristic characters were relatively low. The vertebral count and the number of plicae were the most stable characters in the sample studied, while the anal- and pectoral fin ray counts proved to be the most variable ones. Meristic characters can be described by the formula: D (47-49) 50-55, P (10) 11-12 (13), A (24, 25) 26-30 (31), sp.br. (21) 22-27 (28), vt. 61-67 (68). The morphometric relations showed a tendency to allometry, only the postdorsal and postorbital distances showed almost the isometric pattern of growth. The head characters expressed as proportion of the head length showed a very low variability. The strongest negative relations, on the course of exponential curve, were recorded in the following characters: (first) depth of head, eye diameters, jaws length, interorbital distance (associated with the head length); (second) predorsal distance (associated with the fin arrangement), minimum and maximum body depths and length of caudal fin (the features associated with the body shape). Conclusion. The mean vertebral count obtained in the present study indicates the sampled sandeel from the Gulf of Gdańsk to belong to the autumn-spawning component of the stock. The sandeel is a species of relatively short lifespan, the age group IV was the oldest one and the least numerous in the sample (3.38% of the all specimens). The head length and pectoral fin rays count may be regarded as the characters differentiating the Baltic and Atlantic populations, however more detailed study from different areas of the Baltic Sea is urgently needed to confirm this assumption

Growth rate and condition of vimba, Vimba vimba (Actinopterygii: Cypriniformes: Cyprinidae), a species under restitution in the Odra River estuary

Background. The majority of European populations of vimba, Vimba vimba (L.), have been classified into increasing categories of conservation status while Polish populations of this fish are classified as CR (critically endangered) and in fact they are facing extinction. In many rivers in Poland, including the Odra River, restitution efforts of vimba have been undertaken. Monitoring some biological parameters of the population such as the rate of growth (increase in mass and length), age structure, sex structure, and condition nay help to evaluate the success rate of the restitution efforts. Materials and methods. In total, 210 individuals of vimba, caught in the waters of the southern part of the Odra River estuary, mainly in Lake DÄ…bie, between 28 May 2007 and 30 June 2008 were studied as to their age, condition, rate of growth in mass and length. Making use of the linear R–L dependence, the back calculations were made according to the Rosa Lee procedure with a standard of 20 mm. Results were approximated by 5 mathematical models of growth proposed by von Bertalanffy, Ford–Walford, Gompertz, and based on second degree polynomial function and modified power function. Increase in mass was described by a modified von Bertalanffy equation. The condition of the fish was described by the Fulton (K) and Le Cren (Lc) formulae. Results. Females dominated in the material studied, they constituted over 61% of all individuals. In the age structure groups, females were most often found in groups: 10+ (13.33%), 9+, and 11+ (12.86% each). Males were found in the greatest number among 5-, 6-, and 7-year-old fish (4+, 5+, and 6+, respectively). The mean standard length and mass of the vimba fish studied were 306.33 mm and 286.02 g, respectively. The annual increase in length of the fish approximated 20 mm, being the most intense in the first two years of life (23–24 mm). Fulton and Le Cren coefficients of condition were 0.93 and 1.64 and the ranges of these values were 0.69–1.47 and 1.15–2.60, respectively. Conclusion. Analysis of back readings and empirical results proved that the growth of vimba was best approximated by the von Bertalanffy model. Comparative analysis of condition coefficients of the population of vimba in the Odra River estuary and other populations showed that the condition of analysed vimba population in individual years of live was lower