Environmental filters explain the ecomorphological patterns of stream fish in the southern Amazon

SEABRA, Lidia Brasil; PALHETA, Giovanni Sampaio; BENONE, Naraiana Loureiro; AYRES SANTOS, Bruno; MONTAG, Luciano Fogaça de Assis

doi:10.1590/1809-4392202203192

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Biodiversity and Conservation • Acta Amaz. 53 (3) • Jul-Sep 2023 • https://doi.org/10.1590/1809-4392202203192 copy

Environmental filters explain the ecomorphological patterns of stream fish in the southern Amazon

Authorship SCIMAGO INSTITUTIONS RANKINGS

ABSTRACT

The ecomorphology reflects morphological variations that may indicate significant ecological processes. In this study, the influence of environmental variables on the ecomorphological composition of stream fish was tested. The study was developed in ten streams within a conservation area in the Juruena River sub-basin, in Mato Grosso state, Brazil. The sampling occurred during the drought period in July 2012. The fish were sampled with simple sieves and trawl nets. We analyzed 17 variables of the physical habitat and 14 morphological indices based on morphometric measurements of the fish. In total, 753 specimens were collected, comprising four orders, 14 families, and 27 species. Only fine sediments influenced the ecomorphological composition of the fish assemblages. This substrate variable acted as a filter for the ecomorphology of fish that usually inhabit slow waters, have a morphology adapted towards a good stabilization capacity and maneuverability, fins capable of large and rapid impulses, and that feed close to the surface. Our results can contribute to the understanding of the ecological processes that drive the composition of fish assemblages in conserved Amazonian streams.

KEYWORDS:
ichthyology; conserved streams; fine sediments; habitat morphology

Taxon	N	Species code
Characiformes	606	-
Characidae	392	-
Astyanax gr. bimaculatus	51	Astybima
Hemigrammus sp.	146	Hemisp1
Jupiaba pirana Zanata, 1997	6	Jupipira
Knodus sp.	165	Knodsp1
Moenkhausia oligolepis (Günther, 1864)	24	Moenolig
Crenuchidae	5	-
Characidium zebra Eigenmann, 1909	5	Charzebr
Erythrinidae	91	-
Erythrinus erythrinus (Bloch e Schneider,1801)	89	Eryteryt
Hoplias malabaricus (Bloch, 1794)	2	Hoplmala
Lebiasinidae	118	-
Lebiasina sp. 1	105	Lebisp1
Lebiasina sp. 2	13	Lebisp2
Gymnotiformes	29	-
Gymnotidae	18	-
Gymnotus carapo Linnaeus, 1758	18	Gymncara
Hypopomidae	3	-
Brachyhypopomus beebei (Schultz, 1944)	1	Bracbeeb
Brachyhypopomus brevirostris (Steindachner, 1868)	2	Bracbrev
Sternopygidae	8	-
Eigenmannia aff. trilineata	8	Eigetril
Cichliformes	7	-
Cichlidae	7	-
Aequidens epae Kullander, 1995	6	Aequepae
Crenicichla inpa Ploeg, 1991	1	Creninpa
Siluriformes	111	-
Auchenipteridae	2	-
Centromochlus sp.	2	Centsp1
Callichthyidae	4	-
Callichthys callichthys (Linnaeus, 1758)	3	Callcall
Corydoras sp.	1	Corysp1
Heptapteridae	8	-
Mastiglanis asopos Bockmann, 1994	2	Mastasop
Myoglanis sp.	6	Myogsp1
Loricariidae	90	-
Ancistrus verecundus Fisch-Muller, Cardoso, da Silva e Bertaco, 2005	36	Ancivere
Farlowella amazonum (Günther, 1864)	19	Farlamaz
Hisonotus bockmanni Carvalho e Datovo, 2012	30	Hisobock
Rineloricaria sp.	5	Rinesp1
Pimelodidae	2	-
Pimelodella cristata (Müller e Troschel, 1849)	2	Pimecris
Pseudopimelodidae	5	-
Microglanis poecilus Eigenmann, 1912	5	Micrpoec
Grand total	753	27

Environmental variables	PCA1	PCA2
Mean width-depth ratio	0.64	-0.17
Sand (%)	0.80	0.35
Fine sediments (%)	-0.77	0.34
Falls/cascade/rapids/riffle (%)	0.66	-0.28
All types of pool (%)	0.36	-0.53
Number of wood fragments in channel	0.33	0.71
Volume of wood fragments in channel	0.35	0.72
Undercut bank areal cover	-0.44	-0.58
All fish shelter types	-0.70	0.39
Broken stick model	2.83	1.83
Eigenvalues	3.11	2.14
Variance explained (%)	34.51	23.74
Cumulative variance explained (%)	34.51	58.25

Ecomorphological index	Index code	PC1	PC2
Fineness coefficient	FC	-0.66	-0.67
Compression index	CI	0.62	-0.62
Relative body depth	RBD	0.20	0.78
Relative caudal peduncle length	RCPL	0.17	-0.82
Caudal peduncle compression index	CPCI	-0.28	0.69
Pectoral fin aspect ratio	PFAR	-0.30	-0.06
Index of ventral flattening	IVF	-0.13	-0.44
Relative eye position	REP	0.26	-0.31
Relative head length	RHL	0.56	0.65
Relative mouth width	RMW	0.72	0.51
Relative area of dorsal fin	RADF	0.87	-0.18
Relative area of pectoral fin	RAPF	0.88	-0.32
Relative area of caudal fin	RACF	0.88	0.17
Mouth orientation	MO	-0.44	0.72
Broken-stick model	-	3.25	2.25
Eigenvalue	-	4.46	4.23
Variance explained (%)	-	31.86	30.20
Cumulative variance explained (%)	-	31.86	62.06

Streams	Ecomorphological indices
Streams	RBD	RCPL	RMW	RADF	RAPF	RACF	MO
MT01	0.10	0.29	0.43	1.02	0.95	0.86	-0.74
MT02	0.66	-0.45	0.27	-0.50	-0.42	-0.18	0.56
MT03	0.74	-0.51	0.63	-0.28	-0.37	-0.24	0.45
MT04	0.57	-0.43	0.54	-0.49	-0.34	-0.17	0.58
MT05	0.55	-0.19	0.04	-0.22	0.41	0.44	0.17
MT06	0.97	-0.38	0.20	-0.45	-0.16	-0.03	0.32
MT07	0.76	-0.77	-0.16	-0.11	-0.47	0.10	0.41
MT08	0.30	0.01	-0.24	0.31	0.06	0.30	-0.25
MT09	0.52	-0.43	0.94	-0.40	-0.34	-0.34	0.48
MT10	0.68	-0.39	0.05	-0.37	-0.03	0.22	0.50

Ecomorphological indices	Code	Fine sediments (%)
Relative body depth	RBD	0.64
Relative caudal peduncle length	RCPL	-0.62
Relative mouth of width	RMW	0.44
Relative área of dorsal fin	RADF	-0.66
Relative area of pectoral fin	RAPF	-0.72
Relative area of caudal fin	RACF	-0.83
Mouth orientation	MO	0.63

Variable block	Variable	Mean ± SD	Exclusion method
Channel morphology	Mean wetted width (m)	4.1 ± 3.1	-
Channel morphology	Mean width-depth ratio (m/m)	10.6 ± 2.5	Spearman correlation (≥ 0.60)
Substrate	Sand (0.6-2mm) (%)	31.4 ± 19.1	-
	Fine sediment (silt/clay < 0.6mm) (%)	20.1 ± 9.4	-
	Organic matter (%)	34.8 ± 21.5	-
	Fine roots (%)	3.0 ± 4.5	Spearman correlation (≥ 0.60)
Channel habitat units	Falls/cascade/rapids/riffle (%)	64.2 ± 31.0	-
Channel habitat units	All types of pool (%)	1.9 ± 2.5	Spearman correlation (≥ 0.60)
Declivity	Slope (%)	4.5 ± 4.6	Spearman correlation (≥ 0.60)
Declivity	Channel Sinuosity	1.2 ± 0.3	Spearman correlation (≥ 0.60)
Riparian vegetation cover	Mean canopy density mid-stream (%)	83.5 ± 10.4	-
Riparian vegetation cover	Total riparian cover (Sum of Canopy + Mid-Layer + Ground Cover) (%)	242.5 ± 31.1	-
Large woody fragments*	Number of wood fragments in the channel/150m - Size class 2* (%)	7.5 ± 6.3	-
Large woody fragments*	Volume of wood fragments in the channel/150m - Size class 2* (%)	7.0 ± 7.4	Spearman correlation (≥ 0.60)
Instream shelter for aquatic organisms	Coarse litter (%)	33.7 ± 23.6	-
	Undercut bank areal cover (%)	2.9 ± 1.4	Spearman correlation (≥ 0.60)
	All fish shelter types (Sum of areal cover from all fish concealment types except algae and aquatic macrophytes) (%)	102.3 ± 46.3	-

Variable	Code	Measurement
Maximum body depth	MBD	Maximum vertical distance from the back to the ventral of the fish.
Body area (mm²)	BA	Total body area, including head, without fins.
Caudal fin area (mm²)	CFA	Caudal fin area from the insertion of the hypural bones.
Dorsal fin area (mm²)	DFA	Dorsal fin surface area.
Pectoral fin area (mm²)	PFA	Pectoral fin surface area.
Standard length	SL	Distance from the tip of the upper jaw to the insertion of the hypural bones.
Head length	HL	Distance from the tip of the upper mandible to the posterior end of the operculum.
Caudal peduncle length	CPL	Distance from the posterior proximal margin of the anal fin to the posterior margin of the hypural bones.
Maximum length of pectoral fin	LPF	Distance from the anterior margin of the pectoral fin to its posterior margin.
Mouth width	MW	Maximum horizontal distance from side to side of the mouth.
Caudal peduncle width	CPW	Maximum horizontal distance from side to side of the body at the height of the caudal peduncle.
Maximum body width	MBW	Maximum horizontal distance from side to side of the body.
Maximum width of pectoral fin	WPF	Maximum distance between the dorsal and ventral edges of the fin, forming an angle perpendicular to the line that joins the anterior and posterior margins of the fin.
Maximum midline depth	MMD	Maximum vertical distance from the midline to the belly. Midline is defined as the imaginary line that goes from the pupil of the eye and passes through the center of the last vertebra.
Mouth angle (°)	MA	Defined by the angle formed between the tangential plane of both lips and the plane perpendicular to the longitudinal axis of the body when the mouth is open.
Head depth	HD	Vertical distance from the back to the belly through the pupil.
Depth of the eye midline	DEM	Vertical distance from the middle region of the pupil to the ventral region of the head.

Ecomorphological index	Code	Formula	Ecological interpretation
Compression index	CI	MBW MBD	High values indicate compressed fish that prefer habitats with lower water speed (Watson and Balon 1984).
Relative body depth	RBD	MBD SL	Smaller values would indicate fish inhabiting fast waters (Gatz 1979).
Relative caudal peduncle length	RCPL	CPL SL	Long peduncles indicate fish inhabiting turbulent waters and with good capacity for continuous swimming (Watson and Balon 1984).
Caudal peduncle compression index	CPCI	CPL CPW	High values indicate compressed peduncles, which is typical of fish with less active swimming (Gatz 1979).
Fineness coefficient	FC	$\frac{SL}{\sqrt{MBD x MBW}}$	Values 2 to 6 indicate reduced drag; the optimal ratio for efficient swimming is 4.5 (Ohlberger et al. 2006).
Index of ventral flattening	IVF	MMD MBD	Smaller values indicate fish inhabiting environments with high hydrodynamics, allowing to maintain their spatial position even when stationary (Hora 1930).
Relative area of dorsal fin	RADF	DFA BA	Larger relative areas of dorsal fins have greater stabilization and deviation capacity (Gosline 1971).
Relative area of pectoral fin	RAPF	PFA BA	High values are related to slow swimming or fish in turbulent waters (Watson and Balon 1984).
Relative area of caudal fin	RACF	CFA BA	High values indicate fins capable of producing large and rapid impulses, necessary for the typical form of swimming of many benthic fish (Webb 1984).
Pectoral fin aspect ratio	PFAR	LPF WPF	High values are related to migratory or continuous swimming species (Wainwright et al. 2002).
Relative head length	RHL	HL SL	High values may indicate fish with the ability to feed on relatively large prey (Gatz 1979).
Relative eye position	REP	DEM HD	High values indicate dorsal eyes, normally found in benthic fish (Pouilly et al. 2003).
Relative mouth width	RMW	MW SL	High values indicate fish with the ability to feed on relatively large prey (Gatz 1979).
Mouth orientation	MO	MA x π	High values are associated with fish that eat close to the surface (Gatz 1979).

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[1] * Corresponding author: lidia_brasil@yahoo.com