Habitat associations of the sharpnose shiner Notropis oxyrhynchus in the upper Brazos River, Texas

Figures & data

Table 1 Chi-square and significance values for generalized linear models in 2003 for six physical and chemical habitat variables used to predict sharpnose shiner presence in the Brazos River, TX, USA in 2003 (n = 425) and 2004 (n = 549)

	2003		2004
Variable	χ^2	P	χ^2	P
Current velocity (m/s)	0.16	0.693	4.42	0.035
Depth (cm)	7.27	0.007	0.94	0.332
Dissolved oxygen (mg/L)	< 0.01	0.996	0.69	0.406
Temperature (°C)	0.1	0.752	3.15	0.076
Conductivity (μS/cm)	1.62	0.203	0.51	0.475
Turbidity (NTU)	2.32	0.127	< 0.01	0.978

Table 2 Model selection for nested generalized linear models for significant habitat variables for sharpnose shiner in the Brazos River, TX, USA

Year	Variable	Model	AIC	Δ AIC
2003	Depth	Month	482.0	90.0
		Month + depth	419.4	27.4
		Month + depth + depth^2	407.0	15.0
		Month + depth + depth^2 + month × depth	392.0	0.0
2004	Current velocity	Month	541.0	10.3
		Month + velocity	539.8	9.1
		Month + velocity + velocity^2	536.3	5.6
		Month + velocity + velocity^2 + month × velocity	530.7	0.0

Figure 1 Fitted probabilities of logistic regression models for sharpnose shiner presence and frequency of depths for samples taken monthly from April 2003 through March 2004. Black dots represent the presence or absence of sharpnose shiner in each of the 50 seine hauls made during each month. Sharpnose shiner were absent in all samples during the months (August, December 2003 to February 2004) for which results are not presented

Figure 2 Fitted probabilities of logistic regression models for sharpnose shiner presence and frequency of current velocities for samples taken monthly from April 2004 through March 2005. Black dots represent the presence or absence of sharpnose shiner in each of the 50 seine hauls made during each month. Flood conditions prevented sampling during November 2004