Responses of three PIT-tagged native fish species to floods in a small, upland stream in New Zealand

Figures & data

Table 1  An example showing how a substrate size score was calculated for each grid square.

Size class	(A) Minimum size class axis length (mm)	(B) Proportion of grid square comprising size class	A×B
Boulders	256	0.5	128
Large cobbles	128	0.3	38.4
Small cobbles	64	0.0	0.0
Large gravel	16	0.0	0.0
Small gravel	2	0.15	0.3
Sand	0.5	0.05	0.025
Silt	0.1	0.0	0.0
Bedrock	0	0.0	0.0
		Total (substrate size score):	166.73
Note: The proportion of the benthos of each grid square that was covered in each particle size class was estimated in the field with the aid of a bathyscope. Particle size classes were taken from Wentworth (1992) plus sand, silt and bedrock were assigned lengths of 0.5, 0.1 and 0 mm, respectively).

Table 2  Summary information for 120 native freshwater fish that were implanted with 12.5-mm passive integrated transponder (PIT) tags in the Mangaore Stream, New Zealand in 2008.

Scientific name	Common name	Number tagged in January	Number tagged in March	Number detected during floods
Galaxias brevipinnis	Kōaro	18	11	6
Galaxias postvectis	shortjaw kōkopu	7	15	3
Gobiomorphus huttoni	redfin bully	25	42	22
Total		50	68	31
Note: Table shows the number of fish that were redetected at least once during 40 repeat surveys (to collect data for a separate study) of a 100-m study reach and the number of fish that were redetected at least once during one of four surveys that were undertaken during two flood events that occurred in April and July.

Table 3  Numbers of passive integrated transponder (PIT)-tagged fish that were detected in a 100-m reach of the Mangaore Stream, Manawatu, New Zealand before and after two floods in 2008.

	Tagged population (within study reach) size
Species	Before January flood	After January flood	Before April flood^1	After April flood
Redfin bully	25	13	52	37
Shortjaw kōkopu	7	4	18	11
Kōaro	18	11	22	10
Total	50	28	92	58
Note: ^1Before April flood figures comprise those remaining after the January flood plus an additional group of fish that were tagged within the reach in March (n=39, 14 and 11 for redfin bully, shortjaw kōkopu and kōaro, respectively).

Figure 1  Plots showing correlation between stage depth at each sampling occasion (solid line) and community familiarity score (dashed line). Scores were calculated for each sampling occasion based on the number of times each individual fish was found during the previous 10 sampling occasions. 0 = highly unfamiliar; 10 = highly familiar. Shaded area represents the first 10 sampling occasions, for which familiarity was not calculated. Samples 24 and 25 occurred during the April flood and samples 39 and 40 during the July flood.