Spatio-temporal variation in species composition of New Zealand's whitebait fishery

Figures & data

Figure 1. The proportion of īnanga (Galaxias maculatus) in whitebait samples (n ≥ 100 fish) collected over four months from up to 87 rivers around New Zealand.

Figure 2. The proportion of banded kōkopu (Galaxias fasciatus) in whitebait samples (n ≥ 100 fish) collected over four months from up to 87 rivers around New Zealand.

Figure 3. The proportion of kōaro (Galaxias brevipinnis) in whitebait samples (n ≥ 100 fish) collected over four months from up to 87 rivers around New Zealand.

Figure 4. The proportion of giant kōkopu (Galaxias argenteus) in whitebait samples (n ≥ 100 fish) collected over four months from up to 87 rivers around New Zealand.

Figure 5. The mean (+SE) proportion (%) of the six whitebait species in samples (n ≥ 100 fish) taken over three months (September–November 2015) from 15 regions of New Zealand. The number of samples is shown at the base of bars in the īnanga panels. ND = no data. Regions are: Auckland (AUK), Coromandel (COR), Waikato (WKO), Bay of Plenty (BOP), Taranaki (TKI), Manawatu-Wanganui (MWT), Hawke's Bay (HKB), Wellington (WTN), Tasman-Nelson (TAS), Marlborough (MBH), Buller (BUL), Canterbury (CAN), Westland (WTL), Otago (OTA), Southland (STL) and all of New Zealand (NZ). Grey bars are regions where enough samples were taken in each month to allow comparisons with ANOVA.

Figure 6. The proportion (%) of five whitebait species in samples (n ≥ 100 fish) taken from eight rivers (plotted from north to south) over up to six months (July–December 2015).

Table 1. Summary of DISTLM models with indigenous forest cover (%) of a catchment as a predictor of the species composition of the whitebait catch. Also shown are Pearson's correlation coefficients between indigenous forest cover (%) and individual species within months.

Month	Forest cover SS	Residual SS	df	Pseudo-F	R^2	Species	r
September	5591	175,623	1,54	17.19***	0.24	Īnanga	−0.544***
						Kōaro	0.503***
						Banded kōkopu	0.245*
October	20843	113,387	1,76	13.97***	0.16	Īnanga	−0.454***
						Kōaro	0.298**
						Banded kōkopu	0.354**
November	4887	51,621	1,64	6.69**	0.09	Īnanga	−0.354**
						Kōaro	0.250*
						Banded kōkopu	0.379**

Table 2. Mean (±SE) species composition (%) of whitebait samples from all rivers in New Zealand, North Island (both coasts), South Island (east coast) and South Island (west coast) in 1964 (adapted from McDowall 1965) and 2015. For 2015 the ‘kōkopu’ species have been separated into banded, giant and shortjaw kōkopu. The number of samples (n) from each area is shown.

Area	Year	n	Īnanga	Kōaro	Kōkopu	Banded kōkopu	Giant kōkopu	Shortjaw kōkopu
NZ	1964	304	85.2	9.7	5.1	–	–	–
	2015	2909	87.6 (1.2)	4.8 (0.7)	7.1 (0.9)	6.9 (0.9)	0.3 (0.1)	0.0 (0.0)
North	1964	21	95.8 (1.1)	1.2 (0.4)	3.0 (1.1)	–	–	–
	2015	109	88.7 (1.7)	1.5 (0.3)	8.6 (1.5)	8.5 (1.5)	0.1 (0.0)	0.0 (0.0)
Southeast	1964	29	98.5	1.1	0.4	–	–	–
	2015	57	98.4 (0.3)	0.6 (0.1)	1.0 (0.3)	1.0 (0.3)	0.0 (0.0)	0.0 (0.0)
Southwest	1964	139	83.3 (1.9)	11.5 (1.5)	5.2 (0.6)	–	–	–
	2015	68	74.9 (3.7)	12.4 (2.3)	12.7 (2.9)	11.8 (2.9)	0.9 (0.4)	0.0 (0.0)

Table 3. Mean (±SE) species composition (%) of whitebait samples from four Bay of Plenty rivers in 1983 (adapted from Rowe et al. 1992) and in 2015. The number of samples (n) from each river is shown.

River	Year	n	Īnanga	Kōaro	Banded kōkopu	Giant kōkopu	Shortjaw kōkopu
Kaituna	1983	18	89.1	1.5	9.4
	2015*	8	83.5 (11.0)	0.1 (0.0)	1.0 (0.5)	0.0 (0.0)	0.0 (0.0)
Rangitaiki	1983	27	95.5	2	2.6
	2015	3	98.4 (1.6)	0.0 (0.0)	1.6 (1.6)	0.0 (0.0)	0.0 (0.0)
Whakatane	1983	23	70	19.4	10.8
	2015	5	91.4 (3.2)	5.5 (2.0)	3.0 (2.7)	0.0 (0.0)	0.1 (0.1)
Whangaparaoa	1983	10	58.6	10.5	30.9
	2015	2	97.5 (2.2)	0.1 (0.1)	2.4 (2.1)	0.0 (0.0)	0.0 (0.0)

*Smelt (Retropinna retropinna) comprised 15.4 ± 10.5% of the whitebait catch in the Kaituna River with proportions increasing in later months.

McDowall RM. 1965. The composition of the New Zealand whitebait catch, 1964. N Z J Sci. 8(3):285–300.

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Rowe DK, Saxton BA, Stancliff AG. 1992. Species composition of whitebait (Galaxiidae) fisheries in 12 Bay of Plenty rivers, New Zealand: evidence for river mouth selection by juvenile Galaxias brevipinnis (Günther). N Z J Mar Freshw Res. 26(2):219–228.

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