Andrzej Martyniak

Food web manipulation in a small, eutrophic Lake Wirbel, Poland: effect of stocking with juvenile pike on planktivorous fish

In a four year experiment (1988–1991) carried out in a shallow, eutrophic lake, an increase in young-of-the-year pike (Esox lucius) density was used to control planktivorous fish assemblages consisting mainly of small-sized cyprinids: roach (Rutilus rutilus), Leucaspius delineatus, and white bream (Blicca bjoerkna). Stocking with pike fry of ca 30 mm in three successive springs resulted in large-scale mortality among prey of vulnerable sizes. Rotenone treatment at the end of the fourth year showed that roach and white bream populations contained few 0+ to 2+ fish, but very high numbers of 3+ to 6+ fish. By this time, short-lived, slow-growing L. delineatus, with no size refuge from predators, had been driven almost to extinction.

Food-web manipulation in a small, eutrophic Lake Wirbel, Poland: long-term changes in fish biomass and basic measures of water quality. A case study

A whole-lake experiment was carried out for seven years(1988–1994) in a shallow, eutrophic lake. In the first phase(1989–1991), repeated introductions of young-of-the-year pike(Esox lucius) were used to control the density ofjuvenilestages of the dominant planktivores (roach Rutilusrutilus,white bream Blicca bjoerkna and Leucaspiusdelineatus).The successive introductions of juvenile pike were accompaniedbyselective removal of large pike, roach, bream Abramisbramaand white bream. No visible improvement in water quality wasregistered in the first three years. Assessments made afterthelake was treated with rotenone, revealed the high efficiencyofjuvenile pike in controlling prey of vulnerable size. Thoughthefirst three age-classes were nearly exterminated, older fish(3+ to6+) remained abundant enough to keep their planktonic prey incheck. Indeed, the non-altered density of dominant cladoceransindicated that they were still heavily preyed upon. Algalbiomassremained high.In October 1991, rotenone was applied to remove all fish.Immigrating fish were gradually recolonizing the lake fromspring1992 onwards. However, the process was kept under control bycontinued stocking with juvenile pike and intensive fishing.Theyears following the rotenone treatment witnessed aconsiderableimprovement in water quality, with water transparency 30%higher,a significant 2.2-fold decrease in seston dry weight and2.8-folddecrease in algal biomass, averaged for the summer months.Theseevents can largely be attributed to substantial changes in theherbivorous zooplankton, above all increased density of LakeWirbels largest cladoceran, Daphniacucullata.

Gyrodactylus proterorhini Ergens, 1967 (Monogenoidea, Gyrodactylidae) in gobiids from the Vistula River—the first record of the parasite in Poland

During a parasitological survey of two non-native fish species—racer goby Neogobius gymnotrachelus and monkey goby Neogobius fluviatilis—in the Włocławek Reservoir on the lower Vistula River, the monogenean Gyrodactylus proterorhini was recorded for the first time in Poland, and for the first time, the racer goby was listed as the parasite host. Specimens of G. proterorhini were detected on body surface, fins, and gills of the fish studied. In 2006, the monkey goby was infected with the prevalence 41%, racer goby with the prevalence of 47%, at maximal intensity of 6 and 9 parasites per fish, (respectively). The infection level in relation to the fish size and sampling season was also discussed. The presented study supports the hypothesis of progressive introduction of the parasite with gobiids to the colonized areas.

Marking and return method for evaluating the effects of stocking larval vendace, Coregonus albula (L.), into Lake Wigry in 2000-2001

Marking and return method for evaluating the effects of stocking larval vendace, Coregonus albula (L.), into Lake Wigry in 2000-2001 In 2000 and 2001, larval vendace, Coregonus albula (L.), were marked and released into Lake Wigry. The larvae were immersed in alizarin red S. Of the 19.2 million vendace larvae released in 2000, 2 million were marked (10.4% of the overall number of fish released), and in 2001 of the 18.8 million fish released, 7 million were marked (47.8%). In subsequent years, otoliths were excised from caught vendace and the number of them with alizarin marks was determined. It was assumed that all unmarked specimens came equally from natural spawning and stocking assuming that survival is equal in both forms of recruitment. It was confirmed that 82.4% of the vendace caught from the 2000 generation originated from stocking, while this figure was 64.2% of all specimens caught from the 2001 generation. Lake Wigry hosts the most abundant vendace population in Poland, and this stock spawns on a massive scale annually. Even so, the study described herein provides evidence of just how important systematic stocking is to the maintenance of the vendace population in this lake. Zastosowanie metody znakowanie - zwroty do oceny efektów zarybień jeziora Wigry larwami sielawy, Coregonus albula (L.) w latach 2000-2001 W roku 2000 i 2001 przeprowadzono znakowanie w alizarynie S larw sielawy, Coregonus albula (L.), przeznaczonych do zarybienia jeziora Wigry. Spośród 19,2 mln larw sielawy w 2000 roku poznakowano 2 mln (10,4% całkowitej ilości wpuszczonych ryb) a w roku następnym z 18,8 mln ryb, poznakowano 7 mln (47,8%). W kolejnych latach od wszystkich odłowionych sielaw pobierano otolity i ustalano ile z nich posiadało znaczek alizarynowy. Założono, że wszystkie osobniki niepoznakowane pochodzą, w równym stopniu, tak z naturalnego tarła, jak i z zarybień, przyjmując podobną przeżywalność ryb z obu źródeł rekrutacji. Stwierdzono, że w odłowach sielaw z pokolenia 2000 ryby z zarybień stanowiły 82,4%, a z pokolenia 2001 64,2% wszystkich odłowionych osobników. Jezioro Wigry jest zbiornikiem o największej liczebnie populacji sielawy w Polsce, w którym co roku odbywa się jej masowe tarło. Jednak wyniki opisywanych badań świadczą o niezbędności systematycznych zarybień dla utrzymania populacji sielawy w jeziorze.

Feeding ecology of sterlet Acipenser ruthenus L. in the Hungarian section of the Danube River

Feeding ecology of sterlet Acipenser ruthenus L. in the Hungarian section of the Danube River The aim of the study was to describe the feeding habits of sterlet, Acipenser ruthenus L., in the mid section of the Danube (km 1676-1694). The fish were caught in the summers of 1991 and 1992. The food composition of 85 sterlets (mean body length BL = 37.1 cm; body weightW= 540 g) was analyzed. Most of the fish analyzed (98.8%) had full digestive tracts. Sterlet is considered to be a typical benthic feeder. The food analyzed contained insect larvae and pupae (Trichoptera, Chironomidae), amphipods (Corophium sp., Gammarus sp.), bivalves (Bivalvia), polychaetes (Annelida) and barbel, Barbus barbus (L.). The dominant food items in the digestive tracts were larval caddisflies (Trichoptera), Corophium (Amphipoda), and larval Chironomidae. Regardless of sterlet body size, the fish consumed Chironomidae followed by Trichoptera. The remaining components were noted in the food rarely and in small quantities. One exception were bivalves that were a considerable dietary component of the largest sterlet size group. Odżywianie się sterleta Acipenser ruthenus L. w węgierskiej części Dunaju Celem pracy było określenie odżywiania się sterleta, Acipenser ruthenus L. w środkowej części Dunaju (1676-1694 km). Ryby łowiono latem 1991 i 1992 roku. Zbadano treść pokarmow ą 85 sterletów (średnia długość ciała BL = 37,1 cm; masa ciała W = 540 g). Większość analizowanych ryb (98,8%) miała wypełnione przewody. Sterlet uważany jest za typowego bentofaga. W pokarmie analizowanych osobników stwierdzono występowanie larw i poczwarek owadów (Trichoptera, Chironomidae), obunogi (Corophium sp., Gammarus sp.), małże (Bivalvia), wieloszczety (Annelida) oraz brzana Barbus barbus (L.). W przewodach pokarmowych dominowały larwy chruścików (Trichoptera), Corophium (Amphipoda) i larwy Chironomidae. Niezależnie od rozmiarów ciała sterlet zjadał Chironomidae a w następnej kolejności Trichoptera. Pozosta łe składniki były obecne w przewodach pokarmowych rzadko i w niewielkich ilościach. Jednym wyjątkiem były Bivalvia, które stanowiły znaczący komponent diety największej grupy wielkościowej sterleta.

Alizarin mark retention in the otoliths of whitefish (Coregonus lavaretus f. lavaretus L.) from Lake Łebsko, Poland

During the spawning migrations of whitefi sh (Coregonus lavaretus f. lavaretus L.) to Lake Łebsko in Poland during 2009 and 2010, a total of 276 individuals was caught and analysed to determine the retention time of alizarin red S (ARS) marks in their otoliths following marking in 2004 and 2005. ARS marks were visible in the otoliths of 89 specimens, with the oldest fi sh having an age of 5 +. Such mark retention of in excess of 5 years means that bath-marking with ARS is a valuable method for monitoring whitefi sh from Lake Łebsko during a current recovery programme for this endemic population.