Methodological issues affecting the study of fish parasites. I. Duration of live fish storage prior to dissection

Abstract

We tested the ability of parasite species to respond quickly to artificial conditions (e.g. by changing abundance or even decreasing to extinction) while host fish species were being held alive prior to dissection. Prussian carp Carassius gibelio were sampled by electrofishing from 2 ponds alongside the River Dyje (Czech Republic) during 'cold' and 'warm' seasons. All fish were transported to the laboratory in aerated pond water and kept in a 1 m 3 outdoor basin with aged tap water for 6 d. Twenty fish were dissected on consecutive days (total 120 fish for each site). Our results indicated that there was little change in parasite loading over the first 3 d of holding, suggesting no impact on parasitological studies undertaken over this period. From the fourth day, however, overall parasite abundance increased due to rapid reproduction of some parasite species, especially gyrodactylids in the cold season and dactylogyrids in the warm season. Parasite diversity appeared less stable in the warm season, with significant differences being registered as early as the second day. In addition to holding period, environmental conditions during fish holding will also play an important role in parasite community shifts.

Parasite acquisition by the invasive Chinese sleeper ( Perccottus glenii Dybowski, 1877) (Gobiiformes: Odontobutidae) in Latvia and Ukraine

“…Trichodina sp. occur at high abundance in warmer waters (Kvach, Ondračková, et al, 2016), thus they were only recorded in Ukraine and not Latvia, where they are likely to be rare due to the colder climate. Another possible reason of the absence of Trichodina sp.…”

“…In Ukraine, fish were taken from two sampling sites on the Danube delta, Lake Kartal (45.287011N, 28.518269E) Table 1) using either a 10-m beach seine (6-mm mesh) or a 0.5-m long dipnet (0.5-cm mesh) in the vegetation zone (depth 1-m). All fish were placed into canisters filled with the aerated local water and immediately transported to the laboratory, where they were examined for parasites within 48 hr of catching (see Kvach, Ondračková, Janáč, & Jurajda, 2016). Both standard (SL) and total (TL) length of each fish was measured before section, following which the fins, skin, gills, eyes, muscles, viscera and internal organs (gut, liver, gall bladder, spleen, swimming bladder, kidneys, uterine bladder, gonads, mesentery and brain) were examined for parasites.…”

Finding of Pseudobacciger Harengulae (Digenea, Faustulidae) in the Mediterranean Horse Mackerel, Trachurus Mediterraneus (Actinopterygii, Carangidae), from The Gulf of Odessa, Black Sea, Ukraine

“…Th e fi sh were dissected within 48 hrs. as recommended by Kvach et al (2016). Th e digeneans were isolated from the gut, washed in saline and fi xed with hot 4% formalin (Cribb & Bray, 2010).…”

Parasite communities and infection levels of the invasive Chinese sleeper Perccottus glenii (Actinopterygii: Odontobutidae) from the Naab river basin, Germany

“…All fish were sampled using electrofishing and transported alive to the Institute of Vertebrate Biology of the Academy of Sciences of the Czech Republic (Brno, Czech Republic) in aerated barrels. The fish were kept alive in two outdoor basins (fish from the two different localities separated) and dissected within 3 days of collection (see Kvach et al , 2016b).…”

“…First, preserving fish in ethanol could result in loss of some parasite species or problems with identification (Zander, 2004). More recent studies have shown that keeping fish alive until needed for parasitological dissection greatly improves the accuracy of parasitological community determination (Kvach et al , 2016b). Second, as the Chinese sleeper matures at around 6 cm (Kottelat & Freyhof, 2007); the 2–4 cm size group used in the study clearly represents immature 0+ specimens.…”