Effects of salinity on osmoregulation, growth and survival in Asian swamp eel (Monopterus albus)(Zuiew 1793)

Abstract

The Asian swamp eel Monopterus albus is normally considered a freshwater species, but can also occasionally be found in brackish water. It is an obligate air-breather with highly reduced gills, making its osmoregulation physiology interesting because the gills normally represent the primary site of osmoregulation in teleosts. Being a popular fish for human consumption, the swamp eel is cultured extensively in freshwater ponds in the Mekong Delta of Vietnam. However, very little is known about its salinity tolerance, which is becoming topical due to the increasing salt-water intrusions into tropical deltas. We therefore studied how increased salinity affects survival, growth, blood pressure, heart rate, blood osmolality and plasma ions. All eels survived prolonged exposure to 5 and 10 g L À1 , although plasma osmolality increased significantly at 10 g L À1 . Further elevation to 15 and 20 g L À1 was associated with significantly elevated mortality, with a corresponding increase in plasma osmolality and ion concentrations. Our results show that swamp eels thrive in 0-10 g L À1 with an optimum growth between 0 and 9 g L À1 , indicating that utilization of low saline brackish waters for aquaculture is possible.

Increased gastrointestinal blood flow: An essential circulatory modification for euryhaline rainbow trout (Oncorhynchus mykiss) migrating to sea

“…Increased environmental salinity may also indirectly affect cardiovascular function through dehydration, resulting in decreased blood volume and increased viscosity due to haemoconcentration1314. Knowledge concerning the cardiovascular responses of fish exposed to changes in environmental salinity remains scarce.…”

Osmoregulatory adaptations of freshwater air-breathing snakehead fish (Channa striata) after exposure to brackish water

“…Under SW-FW condition, rapid loss of Na + and Cl − and a brief stress were observed, and the considerably higher activity of Na + /K + -ATPase of SW-SW and SW-FW fish, as compared to FW-adapted fish, remained unchanged. Hence, the snakehead was capable of adapting to salt-dissolved brackish water, similar to other freshwater teleosts, e.g., climbing perch (A. testudineus) ), Asian swamp eel (M. albus) (Pedersen et al 2014), white sucker (Catostomus commersoni) ( Fig. 3 a Changes in plasma glucose and b plasma lactate in C. striata after an abrupt transfer from fresh water to salt-dissolved brackish water (FW-SW), or from fresh water to fresh water (FW-FW).…”

“…Previous reports revealed that air-breathing fish, namely Monopterus albus (Pedersen et al 2014), Anabas testudineus , and Clarias batrachus (Sarma et al 2013), could survive in brackish water. Specifically, M. albus thrived in 10 ‰ salinity, while A. tesudineus tolerated up to 30 ‰.…”

“…In addition, a decrease in plasma free water also raised the hematocrit in snakehead, similar to that observed in white sucker (C. commersonii) (Wilkes and McMahon 1986). In Asian swamp eel, hematocrit decreased after a long exposure to saline water (Pedersen et al 2014). However, hematocrit was not altered in some other species, such as goldfish (C. auratus), tilapia (O. mossambicus), and gray snapper (Lutjanus griseus) after a direct salinity exposure (Luz et al 2008;Kammerer et al 2010;Serrano et al 2011).…”

Optimization of salinity range for rearing glass eel Anguilla bicolor bicolor

“…This result is confirmed by the lowest value of oxygen consumption compared to other salinity treatments (Table 1). Petersen et al (2014), stated that eels survived prolonged exposure to 5 and 10 g/L, although plasma osmolality increased at 10 g/L Boeuf and Payan (2001) suggested that salinity also affects the secretion of hormone, standard metabolism, appetite and feed conversion. Treatment of 10 g/L resulted in the lowest oxygen consumption rate of eel seeds during 14 days of fasting compared to other salinity treatments.…”