Physiological responses of a juvenile marine estuarine-dependent fish (Family Sparidae) to changing salinity
Estuaries are subject to high environmental variability coupled to tidal salinity shifts. Under restricted freshwater flow and prolonged drought conditions, salinity may exceed natural ranges and thus organisms may experience stressful hypersaline conditions. This study assessed the physiology of a juvenile marine estuarine-dependent species Rhabdosargus holubi (Family: Sparidae) under changing salinity to determine the impact on respiration and survival under shock and acclimatisation exposures. Oxygen consumption was not significantly different in the 2.5 to 45 salinity range and the interaction between temperature and salinity was not significant at the moderate levels tested. This confirmed the strong osmoregulatory capabilities of marine estuarine-dependent R. holubi. However, respiration was impacted at salinities of 55–62.5. The salinity tolerance ranges of R. holubi were expanded beyond those previously observed in the laboratory, to a maximum of 77 when fish were gradually exposed to daily 20% incremental changes. This indicated the ability to adapt to hypersaline conditions that occur gradually in anthropogenically altered estuaries which is an important aspect for management decisions regarding freshwater inputs. The adaptability of Rhabdosargus holubi to hypersaline conditions in estuaries may thereby ensure the maintenance of populations in the short term under certain environmental conditions, such as those currently occurring in a freshwater-scarce South Africa. However, in the long term and at more extreme salinities (> 55), the physiology of R. holubi and similar species may be compromised, thus placing the species at risk.
KeywordsBream Drought tolerance Hypersalinity Respiration
This research was funded by the National Research Foundation (NRF) and the Department of Science and Technology (DST) as part of the South African Research Chairs Initiative (SARChI). Further bursary support was kindly provided by the Nelson Mandela University (NMU). Dr. S Paul thanks the Department of Science & Technology, Govt. of India, especially the DST Inspire Faculty Award (DST/INSPIRE/04/ 493 2016/000036) for his fellowship and the University of Calcutta for providing facilities during manuscript preparation.
Compliance with ethical standards
Ethics clearance was obtained from the Animal Ethics Committee of Nelson Mandela University under the protocol A14-SCI-ZOO-001.
Any opinions, findings and conclusions or recommendations expressed in this work are those of the authors and the NRF does not accept any liability in this regard.
- Adams JB, Cowie M, Van Niekerk L (2016) Assessment of completed ecological water requirement studies for South African estuaries and responses to changes in freshwater inflow WRC report no KV 352/15. Water Res Comm 57Google Scholar
- Boehlert GW, Mundy BC (1988) Roles of behavioral and physical factors in larval and juvenile fish recruitment to estuarine nursery areas. Am Fish Soc Symp 3:51–67Google Scholar
- Brauner CJ, Gonzalez RJ, Wilson JM (2013) Extreme environments: hypersaline, alkaline and ion-poor waters fish physiology: euryhaline fishes, vol 32. Academic Press, Oxford, pp 435–476Google Scholar
- DEA (2013) Department of Environmental Affairs: Long-term adaptation scenarios flagship research programme (LTAS) for South Africa. Climate Change Implications for Marine Fisheries in South Africa, Pretoria, p 60Google Scholar
- Götz A, Cowley PC (2013) Cape stumpnose (Rhabdosargus holubi). In: Mann BQ (ed) Southern African marine linefish species profiles Special Publication, vol 9. Oceanographic Research Institute, Durban, pp 268–269Google Scholar
- Nel L, Strydom NA, Perissinotto R, Adams JB, Lemley DA (2017) Feeding ecology of Rhabdosargus holubi (Family Sparidae) in multiple vegetated refugia of selected warm temperate estuaries in South Africa. Estuar Coast Shelf Sci 197:194–204. https://doi.org/10.1016/j.ecss.2017.08.026 CrossRefGoogle Scholar
- Paul S, Kumar S, Moniruzzaman M, Chakraborty SB (2019) Oxygen consumption of Mystus gulio under combined stress of varying salinity and temperature. Thalassas Int J Marine Sci 35:155–160Google Scholar
- Potter IC, Tweedley JR, Elliott M, Whitfield AK (2013) The ways in which fish use estuaries: a refinement and expansion of the guild approach. Fish fish 1–10. https://doi.org/10.1111/faf.12050
- Swanson C (1998) Interactive effects of salinity on metabolic rate, activity, growth and osmoregulation in the euryhaline milkfish (Chanos chanos). J Exp Biol 201:3355–3366Google Scholar
- Torres F (1991) Tabular data on marine fishes from southern Africa. Part 1: length-weight relationships. Fishbyte 9:50–53Google Scholar
- Tweedley JR, Dittmann SR, Whitfield AK, Withers K, Hoeksema SD, Potter IC (2019) Chapter 30 - hypersalinity: global distribution, causes, and present and future effects on the biota of estuaries and lagoons. In: Wolanski E, Day JW, Elliott M, Ramachandran R (eds) Coasts and estuaries. Elsevier, p 523–546Google Scholar
- van der Vyver JSF, Kaiser H, Potts WM, James N (2013) Using blood plasma cortisol concentration and fish behaviour to determine temperature avoidance in the estuarine-dependent fish species Rhabdosargus holubi (Steindachner, 1881) (Sparidae). J Appl Ichthyol 2013:1–4. https://doi.org/10.1111/jai.12268 Google Scholar
- Whitfield AK (1998) Biology and ecology of fishes in South African estuaries. Ichthyological Monographs of the JLB Smith Institute for Ichthyology, No. 2, GrahamstownGoogle Scholar
- Whitfield AK, Bruton MN (1989) Some biological implications of reduced fresh water inflow into eastern cape estuaries: a preliminary assessment. S Afr J Sci 85:691–694Google Scholar
- Whitfield AK, Paterson AW (1995) Flood-associated mass mortality of fishes in the Sundays estuary. Water SA 21:385–389Google Scholar
- Whitfield AK, Blaber SJM, amp CDP (1981) Salinity ranges of some southern African fish species occurring in estuaries. Afr Zool 16:151–155Google Scholar