Dissolved oxygen criteria for freshwater fish in New Zealand: a revised approach

Figures & data

Table 1 Summary of USEPA (1986) dissolved oxygen thresholds (independent of temperature) associated with differing levels of production impairment in salmonids (mg/l).

Degree of impairment	Early life stages	Other life stages
No production impairment	11.0^a (8.0)	8.0
Slight production impairment	9.0^a (6.0)	6.0
Moderate production impairment	8.0^a (5.0)	5.0
Severe production impairment	7.0^a (4.0)	4.0
Limit to avoid acute mortality	6.0^a (3.0)	3.0

^a Recommended water column concentrations to achieve the required inter-gravel oxygen concentrations shown in parentheses.

Table 2 Proposed dissolved oxygen levels for protection of New Zealand freshwater fish communities (independent of water temperature).

	Dissolved oxygen concentration (mg/l)
7-day mean
Guideline	8.0
Imperative	7.0
7-day mean daily minimum
Guideline	6.0
Imperative	5.0
Instantaneous minimum
Guideline	5.0
Imperative	3.5

Imperative protection level is the minimum recommended protection level for adult fish. Guideline protection level should be the target protection level or minimum for salmonids and the early life stages of all species. For salmonid spawning redds or embryonic stages of fish, this should be the interstitial concentration.

USEPA 1986. Ambient water quality criteria for dissolved oxygen. United States Environmental Protection Agency. 46 p.

 Google Scholar