Behavioural response of fishes to increasing pH and dissolved oxygen: field and laboratory observations

Abstract

I 1. Freshwater fish assemblages were sampled quantitatively before, during, and after naturally produced conditions of elevated pH and dissolved oxygen (DO) that occurred for 2-6 h in two dense macrophyte beds. Field observations were followed by 3-4-h laboratory behavioural experiments in which banded killifish (Fundulus diaphanus), bluegill {Jjcpomis macrochirus), and striped bass (Morone saxatilis) were exposed to gradually increasing levels of: (i) pH; (ii) DO; and (iii) pH and DO. 2. Field results indicated that the macrophyte bed dominated by Hydrilla verticillata had a higher fish density than the mixed-spedes (H. verticillata and Vallisneria americana) bed, but beds did not differ significantly in fish species richness or biomass. Within beds, diel changes in fish spedes composition, richness, density and biomass were minor. 3. In the laboratory, avoidance of pH levels exceeding 9.5 was exhibited by all spedes tested. No significant response was observed to either DO increase treatments, or to pH and DO increase treatments. 4. Results suggest fishes do not avoid areas, such as dense macrophyte beds, when high pH levels (9.5-10.0) are accompanied by high DO levels (200-260% saturation). 53

Avoidance behaviour of freshwater fish and shrimp exposed to ammonia and low dissolved oxygen separately and in combination

“…Chronic exposure tests do assess impacts over a longer term, but are expensive, timeconsuming, and are rarely conducted over an animal's entire life cycle (La Point et al 1989). In recent years, more attention has focused on behavioural tests as an alternative method for assessing sub-lethal impacts of contaminants (e.g., Birge et al 1993;Serafy & Harrell 1993;Little & DeLonay 1996;Boubee et al 1997;MacquartMoulin 1997).…”

Effects of freshwater canal discharge on fish assemblages in a subtropical bay:field and laboratory observations

“…While supplementing field work with laboratory studies has increased the understanding of the effects of extremes in turbidity (e.g. Cyrus & Blaber 1987a, b) and pH (Serafy & Harrell 1993) on temperate estuarine fishes, this combined approach has not been fully applied to the problem of salinity change in subtropical bays. We suggest that future research examine the relative importance of duration, Intensity and frequency of freshwater pulses on marine fish assemblages using a combination of field and laboratory investigations.…”

Blinded by the stink: Nutrient enrichment impairs the perception of predation risk by freshwater snails

“…Our preliminary review of the evidence suggests that elevated pH is not an uncommon occurrence. Well known ecosystems with maximum pH values .9.0 include Florida Bay (Lapointe and Matzie 1996), Lake Apopka (Reddy and DeBusk 1991), and Chesapeake Bay (Serafy and Harrell 1993). O'Brien and deNoyelles (1975) report pH values as high as 11.0 in nutrient enriched ponds, and note that ''there are numerous records of such high pH values in small lakes and ponds.''…”

“…Even in systems with low carbonate availability, inorganic carbon is generally replenished by respiration, so depletion tends to be local and temporary (Talling 1976). Inorganic carbon depletion is expected to occur in surface waters if thermal stratification prevents mixing with deeper waters, or it may occur within dense beds of macrophytes if the macrophytes themselves inhibit mixing (e.g., Serafy and Harrell 1993). pH in productive systems will follow a diel pattern, peaking in mid-to-late day and falling at night (Maberly 1996).…”