Opportunistic reproductive strategy of a non-native fish, the spotted metynnis Metynnis maculatus (Kner, 1858) (Characidae Serrasalminae) in a tropical reservoir in south-eastern Brazil

Figures & data

Table 1 χ² Test for sex ratio comparisons by size classes of M. maculatus in the Lajes reservoir, 2005/06.

Size class (TL mm)	Males (n)	Females (n)	Sex ratio	Total	EF	Significance
100–110	2	0	2.0:0.0	2	1.0	n.s.
110–120	1	1	1.0:1.0	2	1.0	n.s.
120–130	5	1	5.0:1.0	6	3.0	n.s.
130–140	14	5	2.8:1.0	19	9.5	n.s.
140–150	35	11	3.2:1.0	46	23.0	*
150–160	35	23	1.5:1.0	58	29.0	n.s.
160–170	7	35	1.0:5.0	42	21.0	**
>170	1	22	1.0:22.0	23	11.5	**
Total	100	98	1.0:1.1	198	99.0	n.s.
Note: TL, total length (mm); n, number of individuals; EF, expected frequency; **significant at 99% level of confidence; *significant at 95% level of confidence; n.s., non-significant.

Figure 1 Transversal section of ovarian tissue. (A) o, oogonia; eps, early perinucleolar stage; cn, chromatin nucleolar stage; (B) eps, early perinucleolar stage; yn, yolk nucleus; lps, late peri-nucleolar stage; n, nucleus; y, cortical alveoli formation; no, nucleoli; yn, yolk nucleus; l, lipid droplets; (C) v, vitellogenesis stage; n, nucleus; l, lipid droplets; (D) v, vitellogenesis stage; zr, zona radiata; l, lipid droplets; yg, yolk granules; (E) r, ripe stage; zr, zona radiata; (F) r, ripe stage; yg, yolk granules; pf, postovulatory follicles. Haematoxylin and eosin stain.

Figure 2 Tubules containing stages of spermatogenesis. (A) s, spermatogonia; ps, primary spermatocytes; ss, secondary spermatocytes; st, spermatids; sz, spermatozoa; ta, tunica albuginea; cy, cysts; (B) ps, primary spermatocytes; ss, secondary spermatocytes; Haematoxylin and eosin stain.

Figure 3 Temporal variation of ovarian (top) and testes (bottom) stages of M. maculatus in the Lajes reservoir. Number of examined individuals is indicated above the bars. A/S, August/September; O/N, October/November; D/J, December/January; F/M, February/March; A/M, April/May; J/J, June/July.

Figure 4 Temporal variation in GSI of M. maculatus (top) and in water level (plus 400 m above sea level), temperature (°C, means+SE) and accumulated rainfall (mm) (bottom) in the Lajes reservoir, from August 2005 to September 2006. Codes of months and number of examined individuals according to Figure 3.

Table 2 F-Values from ANOVA for monthly comparisons of GSI, HSI and K for males and females M. maculatus in the Lajes reservoir.

Parameters	Sex	F	P values	Tukey post-hoc comparisons
GSI	Females	12.06	0.0001**	August–January>February–July
	Males	1.35	0.24 n.s.	–
K	Females	2.62	0.02*	February–March>June–July
	Males	4.8	0.0001**	April–May>August–January
HSI	Females	1.75	0.14 n.s.	–
	Males	0.33	0.92 n.s.	–
Notes: Sample size: 100 males, 98 females. **P < 0.01; *P < 0.05; n.s., non-significant.

Figure 5 Temporal variation in condition factor (K) and hepatossomatic index (HSI) for both sexes of M. maculatus in the Lajes reservoir. Codes of months and number of examined individuals according to Figure 3.

Figure 6 Relationships between Fecundity and TL (top), gonad weight (middle) and body weight (bottom) for M. maculatus in the Lajes reservoir.