Abstract
The present paper deals with the breeding biology of the invasive fish Pterygoplicthys pardalis from the natural drainages of Thiruvananthapuram, Kerala. The specimens were collected from Amayizhanchan Thodu, a natural drainage running through the heart of the city. A total of 145 males and 142 females were collected from January to December 2018. The sex ratio was determined monthly as the percentage of males to females (M: F). Monthly mean gonadosomatic index (GSI) values were compared using R stat, and GSI was plotted monthly to identify the spawning seasons. The gonads were examined and different stages of maturity were noted using standard methods. The length at first maturity was also found out. The fish exhibit courtship behaviour and the eggs are deposited in burrows and also along the crevices in the granite walls; the burrows are guarded by the male fish till the young ones are hatched out. The sex ratio showed an average mean value of 1.04: 1 and showed no significant departure. The size at first maturity was 23.9 cm standard length. The ova diameter studies show the presence of ripe ovaries throughout the year, with peaks during March and April and between August and September and in December, indicating the fish is a batch spawner. The absolute fecundity ranges from 923 to 14,777 eggs, and the relative fecundity ranges 0.0142–0.0015. Regression analysis showed a significant relationship (P <0.001) between absolute fecundity and the total length, the total body weight, and ovary weight. The strong breeding behaviour, the presence of accessory respiratory organs, the absence of natural enemies and parental care makes Pterygoplichthys pardalis a successful invader in the natural drainage. More biological studies are needed for the successful eradication of the species from the invaded ecosystem.
Highlights
Reproductive biology is one of the key features considered for the invasion biology studies of fish (Feiner et al 2012; Gutkowsky & Fox 2012; Zahorska et al 2013; Horkova & Kovac 2015)
Our observations reveal that the male fish excavate burrows (Image 2A, B) before spawning for laying eggs
Courtship behaviour was exhibited in the form of circular movements near the burrows (Images 2C–E), by rubbing their bodies with the flashing of water, and in a few cases, multiple males take part in the process, and the eggs are guarded till the young ones emerge from the nest (Image 2F)
Summary
Reproductive biology is one of the key features considered for the invasion biology studies of fish (Feiner et al 2012; Gutkowsky & Fox 2012; Zahorska et al 2013; Horkova & Kovac 2015). The high invasiveness shown by this species is primarily because of its unique biological features, which include the ability to survive in water with varying levels of flow regimes (Nico & Martin 2001; Welcomme & Vidthayanom 2003; Chavez et al 2006; Nico et al 2012), temperature and dissolved oxygen using accessory respiration with diverticula of the gastrointestinal tract (Armbruster 1998; da Cruz et al 2013), and pH (Mendoza et al 2009; Parente et al 2017), a broad range of diet (German et al 2010) and the absence of natural predators (Nico & Martin 2001; Gibbs et al 2008), which enable them to survive in the invaded ecosystems They are salt-tolerant and survive well in brackish water regions (Mendoza et al 2009; Kumar et al 2018). Site selection for spawning, nest building and caring of eggs and the young ones are a complex set of reproductive behaviour among loricariids (Covain & Fisch-Muller 2007)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
