Does one size fit all? An evaluation of length–weight relationships for New Zealand's freshwater fish species

Figures & data

Table 1 Estimated parameters of length–weight relationships for 53 freshwater fish species in New Zealand using wet-weight data (except for Stokellia anisodon which were preserved in formalin). Parameters are given for power equations and 95% CI for a are provided in Table S1. Quadratic parameters are supplied in Table S2 if they were selected as the better model. For the ‘Origin’ column: N = native, I = introduced, M = marine wanderer, E = extinct. NA = not available.

Family Species name (Naming authority)	Common name	Origin	n	Length measure (TL/FL)	Length range (mm)	Weight range (g)	R^2	a	b	95% CI b
Anguillidae
Anguilla australis (Richardson 1841)	Shortfin eel	N	34891	TL	72–1310	0.3–3955	0.975	4.906×10^−7	3.224	3.218–3.229
Anguilla dieffenbachii (Gray 1842)	Longfin eel	N	41070	TL	88–1565	0.7–15000	0.975	3.624×10^−7	3.307	3.301–3.312
Anguilla reinhardtii (Steindachner 1867)	Spotted eel	N	27	TL	408–760	177–1513	0.935	2.975×10^−7	3.360	2.996–3.725
Cyprinidae
Carassius auratus (Linnaeus 1758)	Goldfish	I	3986	FL	15–396	0.05–2435	0.980	1.253×10^−5	3.125	3.111–3.138
Ctenopharyngodon idella (Valenciennes 1844)	Grass carp	I	398	FL	140–604	39.6–3870	0.967	1.086×10^−5	3.049	2.994–3.104
Cyprinus carpio (Linnaeus 1758)	Koi carp	I	2615	FL	45–700	2–8373	0.985	1.694×10^−5	3.048	3.034–3.062
Hypophthalmichthys molitrix (Valenciennes 1844)	Silver carp	I					–	–	–
Leuciscus idus (Linnaeus 1758)	Orfe	I					–	–	–
Scardinius erythrophthalmus (Linnaeus 1758)	Rudd	I	1548	FL	67–340	4–813	0.975	7.525×10^−6	3.168	3.142–3.193
Tinca tinca (Linnaeus 1758)	Tench	I	363	FL	37–510	0.7–1804	0.991	1.797×10^−5	2.983	2.953–3.012
Eleotridae
Gobiomorphus alpinus (Stokell 1962)	Tarndale bully	N					–	–	–
Gobiomorphus basalis (Gray 1842)	Cran's bully	N	17	TL	40–107	0.8–16	0.724	1.027×10^−4	2.494	1.646–3.341
Gobiomorphus breviceps (Stokell 1940)	Upland bully	N	3323	TL	22–131	0.1–30	0.945	1.127×10^−5	3.025	2.999–3.049
Gobiomorphus cotidianus (McDowall 1970)	Common bully	N	1799	TL	16–140	0.03–30	0.983	6.160×10^−6	3.152	3.133–3.171
Gobiomorphus gobioides (Valenciennes 1844)	Giant bully	N	363	TL	86–222	5–180	0.916	6.893×10^−6	3.145	3.046–3.244
Gobiomorphus hubbsi (Stokell 1959)	Bluegill bully	N	625	TL	31–92	0.1–6.5	0.951	1.798×10^−6	3.393	3.332–3.453
Gobiomorphus huttoni (Ogilby 1894)	Redfin bully	N	243	TL	38–111	0.4–17	0.945	2.574×10^−6	3.329	3.227–3.431
Galaxiidae
Galaxias anomalus (Stokell 1959)	Roundhead galaxias	N	5299	TL	36–106	0.2–8.8	0.931	2.345×10^−6	3.269	3.245–3.292
Galaxias argenteus (Gmelin 1789)	Giant kōkopu	N	298	TL	67–340	4.9–644	0.984	7.004×10^−6	3.121	3.075–3.166
Galaxias brevipinnis (Günther 1866)	Kōaro	N	573	TL	37–230	0.3–110	0.966	1.838×10^−6	3.324	3.272–3.375
Galaxias cobitinis (McDowall/Waters 2002)	Lowland longjaw galaxias	N	7455	TL	19–82	0.05–2.9	0.813	4.490×10^−6	3.039	3.006–3.072
Galaxias depressiceps (McDowall/Wallis 1996)	Flathead galaxias	N	1692	TL	26–116	0.1–11	0.962	1.821×10^−6	3.342	3.310–3.373
Galaxias divergens (Stokell 1959)	Dwarf galaxias	N	4772	TL	20–90	0.05–6.3	0.922	6.252×10^−6	3.003	2.978–3.028
Galaxias eldoni (McDowall 1997)	Eldon's galaxias	N	4577	TL	18–156	0.06–37	0.975	3.636×10^−6	3.186	3.171–3.200
Galaxias fasciatus (Gray 1842)	Banded kōkopu	N	1269	TL	38–248	0.2–228	0.982	1.205×10^−6	3.438	3.412–3.464
Galaxias gollumoides (McDowall/Chadderton 1999)	Gollum galaxias	N	6	TL	65–92	2.7–7.3	0.739	1.341×10^−5	2.914	0.510–5.317
Galaxias gracilis (McDowall 1967)	Dwarf inanga	N					–	–	–
Galaxias macronasus (McDowall/Waters 2003)	Bignose galaxias	N	2357	TL	21–110	0.1–9.6	0.833	7.675×10^−6	2.896	2.844–2.949
Galaxias maculatus (Jenyns 1842)	Īnanga	N	1730	TL	36–140	0.2–18	0.962	4.990×10^−7	3.566	3.533–3.599
Galaxias paucispondylus (Stokell 1938)	Alpine galaxias	N	1105	TL	33–120	0.1–9.7	0.897	7.856×10^−6	2.904	2.846–2.962
Galaxias postvectis (Clarke 1899)	Shortjaw kōkopu	N	588	TL	50–243	0.9–204	0.984	2.114×10^−6	3.333	3.299–3.368
Galaxias prognathus (Stokell 1940)	Upland longjaw galaxias	N	386	TL	38–86	0.2–3.4	0.848	3.642×10^−6	3.061	2.932–3.191
Galaxias pullus (McDowall 1997)	Dusky galaxias	N	2765	TL	26–158	0.1–40	0.978	2.307×10^−6	3.295	3.276–3.314
Galaxias ‘sp. D.’	Clutha flathead galaxias	N	1940	TL	26–136	0.1–26	0.972	2.848×10^−6	3.226	3.201–3.250
Galaxias ‘Northern sp.’	Northern flathead galaxias	N					–	–	–
Galaxias ‘Southern sp.’	Southern flathead galaxias	N	20	TL	70–106	3.1–9.7	0.956	1.111×10^−5	2.947	2.634–3.259
Galaxias ‘Teviot’	Teviot flathead galaxias	N					–	–	–
Galaxias vulgaris (Stokell 1949)	Canterbury galaxias	N	1945	TL	28–171	0.1–38	0.957	3.338×10^−6	3.196	3.166–3.226
Neochanna apoda (Günther 1867)	Brown mudfish	N	660	TL	29–162	0.1–23	0.973	4.694×10^−6	3.025	2.986–3.063
Neochanna burrowsius (Phillipps 1926)	Canterbury mudfish	N	1296	TL	30–148	0.1–22	0.938	6.199×10^−6	2.986	2.945–3.028
Neochanna diversus (Stokell 1949)	Black mudfish	N	555	TL	32–157	0.2–24	0.981	5.483×10^−6	3.017	2.982–3.052
Neochanna heleios (Ling/Gleeson 2001)	Northland mudfish	N
Neochanna rekohua (Mitchell 1995)	Chatham mudfish	N
Geotriidae
Geotria australis (Gray 1851)	Lamprey	N	264	TL	23–614	0.1–173	0.972	2.030×10^−5	2.479	2.427–2.530
Ictaluridae
Ameiurus nebulosus (Lesueur 1819)	Brown bullhead catfish	I	5767	FL	42–420	0.8–1129	0.979	5.981×10^−6	3.137	3.125–3.149
Mugilidae
Aldrichetta forsteri (Valenciennes 1836)	Yelloweye mullet	M	28	FL	198–390	107–680	0.980	2.111×10^−5	2.902	2.773–3.070
Mugil cephalus (Linnaeus 1758)	Grey mullet	M	146	FL	138–520	33–2054	0.975	8.632×10^−6	3.078	2.997–3.159
Percidae
Perca fluviatilis (Linnaeus 1758)	Perch	I	3218	FL	23–441	0.1–1614	0.978	1.543×10^−5	2.984	2.968–2.999
Pinguipedidae
Cheimarrichthys fosteri (Haast 1874)	Torrentfish	N	711	FL	31–140	0.4–40	0.977	1.3929×10^−5	2.974	2.940–3.008
Pleuronectidae
Rhombosolea leporina (Günther 1862)	Yellowbelly flounder	M	526	TL	46–369	1.1–721	0.983	1.490×10^−5	2.989	2.955–3.022
Rhombosolea plebeia (Richardson 1843)	Sand flounder	M	503	TL	46–328	1.1–599	0.962	8.476×10^−6	3.117	3.063–3.172
Rhombosolea retiaria (Hutton 1874)	Black flounder	N	355	TL	75–391	5.7–1003	0.944	6.154×10^−5	2.765	2.694–2.836
Poeciliidae
Gambusia affinis (Baird/Girard 1853)	Mosquito fish	I	188	TL	15–51	0.02–2.0	0.906	1.018×10^−6	3.681	3.512–3.860
Poecilia latipinna (Lesueur 1821)	Sailfin molly	I					–	–	–
Poecilia reticulata (Peters 1859)	Guppy	I					–	–	–
Ptereleotridae
Parioglossus marginalis (Rennins/Hoese 1985)	Dart goby	I					–	–	–
Retropinnidae
Prototroctes oxyrhynchus (Günther 1870)	Grayling	E					–	–	–
Retropinna retropinna (Richardson 1848)	Common smelt	N	33270	FL	20–125	0.01–22	0.930	3.612×10^−6	3.105	3.097–3.115
Stokellia anisodon (Stokell 1941)	Stokell's smelt	N	50	FL	70–81	N/A	0.683	2.778×10^−5	2.650	N/A
Salmonidae
Oncorhynchus mykiss (Walbaum 1792)	Rainbow trout	I	84262	FL	38–790	0.5–5550	0.939	2.101×10^−5	2.909	2.904–2.914
Oncorhynchus nerka (Walbaum 1792)	Sockeye salmon	I	47	FL	197–465	88–1336	0.994	2.357×10^−6	3.290	3.212–3.368
Oncorhynchus tshawytscha (Walbaum 1792)	Chinook salmon	I	3640	FL	30–1070	0.1–21110	0.990	6.401×10^−6	3.099	3.089–3.109
Salmo salar (Linnaeus 1758)	Atlantic salmon	I	40	FL	445–724	1134–2948	0.833	5.419×10^−3	1.994	1.701–2.288
Salmo trutta (Linnaeus 1758)	Brown trout	I	17662	FL	22–930	0.1–8172	0.995	1.332×10^−5	2.978	2.975–2.981
Salvelinus fontinalis (Mitchill 1814)	Brook char	I	518	FL	29–235	0.2–147	0.986	9.593×10^−6	3.007	2.975–3.038
Salvelinus namaycush (Walbaum 1792)	Mackinaw trout	I					–	–	–

Table 2 Estimated parameters of length–weight power relationships for New Zealand freshwater fish species for which dry-weight data was available. Quadratic parameters are supplied in Table S3 if they were selected as the better model.

			Length	Length			95%		95%
			measure	range			CI		CI
FamilySpecies name	Common name	n	(TL/FL)	(mm)	R^2	a	a	b	b
Anguillidae
Anguilla australis	Shortfin eel	86	TL	54–385	0.983	2.999×10^−8	1.799×10^−8–4.998×10^−8	3.481	3.382–3.581
Anguilla dieffenbachii	Longfin eel	108	TL	66–647	0.978	1.390×10^−8	7.790×10^−9–2.479×10^−8	3.641	3.535–3.746
Eleotridae
Gobiomorphus breviceps	Upland bully	271	TL	24–94	0.968	2.155×10^−7	1.561×10^−7–2.973×10^−7	3.616	3.537–3.695
Gobiomorphus cotidianus	Common bully	76	TL	14–111	0.982	7.746×10^−7	5.061×10^−7–1.186×10^−6	3.297	3.193–3.402
Gobiomorphus gobioides	Giant bully	3	TL	52–81	0.998	1.227×10^−7	1.150×10^−11–1.309×10^−3	3.712	1.502–5.922
Gobiomorphus hubbsi	Bluegill bully	53	TL	48–76	0.787	1.498×10^−6	2.389×10^−7–9.389×10^−6	3.078	2.629–3.528
Galaxiidae
Galaxias brevipinnis	Kōaro	29	TL	35–105	0.978	1.400×10^−8	4.978×10^−9–2.479×10^−8	4.082	3.839–4.324
Galaxias maculatus	Īnanga	35	TL	42–101	0.917	1.229×10^−7	2.734×10^−8–5.520×10^−7	3.473	3.104–3.843
Galaxias paucispondylus	Alpine galaxias	67	TL	52–95	0.856	1.107×10^−6	2.993×10^−7–4.095×10^−6	3.068	2.757–3.380
Galaxias vulgaris	Canterbury galaxias	217	TL	60–137	0.936	3.831×10^−7	2.240×10^−7–6.550×10^−7	3.417	3.297–3.537
Pinguipedidae
Cheimarrichthys fosteri	Torrentfish	64	FL	49–136	0.984	4.261×10^−7	2.581×10^−7–7.033×10^−7	3.467	3.353–3.580
Salmonidae
Oncorhynchus mykiss	Rainbow trout	25	FL	61–185	0.984	3.472×10^−7	1.503×10^−7–8.020×10^−7	3.407	3.218–3.596
Oncorhynchus tshawytscha	Chinook salmon	68	FL	67–115	0.903	1.092×10^−7	2.906×10^−8–4.102×10^−7	3.735	3.434–4.036
Salmo trutta	Brown trout	221	FL	58–199	0.956	2.294×10^−6	1.560×10^−6–3.373×10^−6	3.050	2.963–3.137

Figure 1 Scatterplot of log₁₀a and b parameters based on body shape for 52 New Zealand freshwater fish species. For clarity, the data point for Atlantic salmon has been omitted from the plot.

Table 3 Differences in length–weight relationships between locations. Equations are only provided for those species where a significant difference between the North and South Islands was detected (the list of species for which no significant differences were detected are in Table S4).

Family
Species name	Common name	Island	n	a	b
Anguillidae
Anguilla australis	Shortfin eel	North	21723	3.9129×10^−7	3.2552
		South	13168	6.1403×10^−7	3.1952
Cyprinidae
Scardinius erythrophthalmus	Rudd	North	1134	7.6776×10^−6	3.1587
		South	414	4.6029×10^−6	3.2792
Eleotridae
Gobiomorphus cotidianus	Common bully	North	1375	6.6481×10^−6	3.1377
		South	423	2.0647×10^−6	3.4027
Galaxiidae
Galaxias argenteus	Giant kōkopu	North	86	1.3902×10^−5	2.9946
		South	212	5.9995×10^−6	3.1485
Galaxias divergens	Dwarf galaxias	North	2691	3.8140×10^−6	3.1286
		South	2081	2.6898×10^−5	2.6320
Galaxias fasciatus	Banded kōkopu	North	513	2.1307×10^−6	3.3208
		South	756	9.6888×10^−7	3.4865
Galaxias maculatus	Īnanga	North	1339	5.8634×10^−7	3.5282
		South	391	1.9799×10^−7	3.7754
Percidae
Perca fluviatilis	Perch	North	3107	1.7488×10^−5	2.9604
		South	111	4.1487×10^−6	3.2190
Pinguipedidae
Cheimarrichthys fosteri	Torrentfish	North	41	5.0381×10^−6	3.2052
		South	670	1.4706×10^−5	2.9616
Salmonidae
Oncorhynchus mykiss	Rainbow trout	North	83180	6.2808×10^−5	2.7335
		South	1082	1.0038×10^−5	3.0225
Salmo trutta	Brown trout	North	10656	1.5335×10^−5	2.9582
		South	7006	1.5114×10^−5	2.9492

Table 4 Differences in length–weight relationships for male and female fishes. Equations are only provided for those species where a significant difference between the sexes was detected. Note that values for a and b may be markedly different to those in Table 1 because less data was used across a more limited size range.

FamilySpecies name	Common name	P value	Sex	n	Range (mm)	a	b	95% CI b
Cyprinidae
Carassius auratus	Goldfish	0.02	Female	144	87–241	6.3760×10^−6	3.252	3.184–3.319
			Male	145	83–239	1.1234×10^−5	3.134	3.072–3.205
Cyprinus carpio	Koi carp	0.005	Female	265	243–633	9.8060×10^−6	3.147	3.029–3.265
			Male	510	231–630	2.6727×10^−5	2.970	2.905–3.035
Galaxiidae
Galaxias brevipinnis	Kōaro	0.01	Female	58	96–192	1.9255×10^−5	2.867	2.721–3.014
			Male	40	96–195	4.4570×10^−6	3.170	2.965–3.375
Percidae
Perca fluviatilis	Perch	0.04	Female	290	117–305	1.0284×10^−5	3.043	2.968–3.118
			Male	118	114–305	5.0490×10^−6	3.186	3.067–3.306
Salmonidae
Salmo trutta	Brown trout	<0.001	Female	846	177–600	5.4749×10^−5	2.742	2.704–2.781
			Male	747	170–605	1.2074×10^−4	2.604	2.558–2.650

Figure 2 The relationship between measured and predicted fish weight for 25 sites around New Zealand. Predicted fish weights were calculated using both power and quadratic equations from Table 1. Note that two separate regression lines are not visible because the fitted relationships were equivalent when both methods were used.