Location and timing of the deposition of egg strands by perch (Perca fluviatilisL.): the roles of lake hydrology, spawning substrate and female size

Abstract

Key-words: SCUBA diving, Aquatic vegetation, Common stonewort, Chara vulgaris, Common reed Phragmites communis, Lake managementThe reproduction biology of perch Perca fluviatilis was studied in relation to lake hydrology, spawning substrate and female size using SCUBA divers during late April and mid-May 2009 in Chabařovice Lake, Czech Republic. An extreme displacement of water mass, induced by a long-lasting strong wind, caused the abundance of egg strands to differ significantly between individual parts of the lake. On average, 91% of perch spawning activity occurred at depths greater than 3 m. The mean concentration of dissolved organic carbon (DOC) indicated that the lake belongs to the category where DOC influencing the penetration of ultraviolet radiation, is not responsible for the deep deposition of egg strands by perch. Most probably, the avoidance of shallow depths (<3 m) results from strong wind/waves coming from any direction. Larger perch females started to spawn earlier than their smaller conspecifics and they used shallower depths for depositing their egg strands. As a spawning substrate, perch strongly selected dead submerged vegetation, such as common reed Phragmites communis and worm weed Artemisia sp. These substrates, however, reveal signs of progressive degradation and seem likely to disappear from the lake within several years. RÉSUMÉLieu et date de la ponte des rubans d'oeufs par la perche (Perca fluviatilis L.) : les rôles de l'hydrologie lacustre du substrat de ponte et de la taille des femelles Mots-clés :plongée sous-marine, végétation aquatique, Chara vulgaris, armoise, roseau commun La biologie de la reproduction des perches Perca fluviatilis a été étudiée en relation avec l'hydrologie lacustre, le substrat de ponte et la taille des femelles par des plongeurs de la fin avril à la mi-mai 2009 dans le lac Chabařovice, République Tchèque. Un déplacement extrême de la masse d'eau, induit par un vent fort de longue durée, a provoqué une abondance des rubans d'oeufs différant considéra-blement entre les différentes parties du lac. En moyenne, 91 % de l'activité de frai des perches est survenue à une profondeur supérieure à 3 m. La concentration moyenne en carbone organique dissous (DOC) indiquant que le lac appartient à la catégorie où le DOC influence la pénétration du rayonnement ultraviolet, n'est pas responsable du dépôt profond de rubans d'oeufs par la perche. Très probablement, l'évitement des faibles profondeurs (<3 m) résulte du vent fort et/ou des vagues venant de n'importe quelle direction. Les plus grandes perches femelles ont commencé à frayer plus tôt que leurs congénères plus petites et elles ont utilisé des profondeurs plus faibles pour le dépôt de leurs rubans d'oeufs. Comme substrat de frai, la perche a fortement sélectionné la végétation morte submergée telle que le roseau commun Phragmites communis et l'armoise. Ces substrats, cependant, montrent des signes de dégradation progressive et semblent susceptibles de disparaître du lac dans quelques années.

Distribution of Herbivorous Fish Is Frozen by Low Temperature

“…It has an area of 250 ha, a volume of 0.036 km 3 and a maximum depth of 25 m. Aquatic restoration started in 2001 and was finished in 2011. Several species of macrophytes and algae are present at high levels of biomass to a depth of 12 m51. The biomass of rudd was 3.58 kg ha −1 in 2013, and 2.50 kg ha −1 in 2014.…”

Fluctuations of perch populations in Lake Geneva from 1984 to 2011 estimated from the number and size of egg strands collected in two locations exposed to different fishing practices

“…Cech et al . () also observed that strong winds influence egg strand distribution in Lake Chabarovice (Czech Republic). However, as this part of the Swiss shore of Lake Geneva is particularly exposed to storms coming from the south‐west, this explanation seems unlikely.…”

“…Probst et al (2009) observed that in Lake Constance large perch egg strands are less abundant than small ones in areas exposed to waves. Cech et al (2011) also observed that strong winds influence 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004 2006 1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004 2006 egg strand distribution in Lake Chabarovice (Czech Republic). However, as this part of the Swiss shore of Lake Geneva is particularly exposed to storms coming from the south-west, this explanation seems unlikely.…”

Thirty-Year-Old Paradigm about Unpalatable Perch Egg Strands Disclaimed by the Freshwater Top-Predator, the European Catfish (Silurus glanis)

“…This size limit was set for two main reasons: 1) The SCUBA diving results from 2007 and 2009 have shown that in Milada Lake 97% and 92% of perch egg strands were spawned by females ≥ 230 mm L T [9, 23]. 2) Based on gillnet catches, almost 90% of perch ≥ 230 mm L T were females [24].…”