Performance of constructed fish spawning and rearing channels – development of the Imatra City Brook in Finland

Figures & data

Figure 1. Location of Imatra City Brook in south-eastern Finland at the Vuoksi river.

Figure 2. Imatra City Brook with its characteristic areas (study sites shown in Figure 4.).

Figure 3. The habitat section was designed with a winding channel and small gradients, with deeper pools in between.

Figure 4. Electrofishing sites 1–5 and macroinvertebrate sites A–D.

Table 1. Brown trout density estimations for age groups 0+ and 1+ juvenile densities (per 100 m²), according to electrofishing results.

	2016	2017	2017
Site	0+	1+	0+
1	63	13	64
2	76	42	3
3	17	62	0
4	41	19	131
5	3	17	17
Average	40	31	43

Table 2. Number of macroinvertebrate taxa and individuals in 2016 and 2017, divided in FFG.

	Number of taxa		Number of individuals
	2016	2017	2016	2017
FIL	4	6	135	463
GAT	4	6	239	911
SCR	6	13	469	5511
SHR	2	6	106	355
PRE	6	12	758	1325
OTHERS	2	4	4	36
TOTAL	24	47	1711	8601

Abbreviations for FFGs are: FIL = filter feeders, GAT = gathering collectors, SCR = scrapers, SHR = shredders, and PRE = predators. The group OTHERS comprises only parasites.

Figure 5. Percentages of individuals attributed to FFGs in Imatra City Brook in 2016 (left) and 2017 (right).

Table 3. Ecological and diversity indices of the macroinvertebrate community in the City Brook in years 2016 and 2017.

	2016				2017
Site	A	B	C	D	A	B	C	D	Refe-rence
Average individuals/ sample	25	62	78	262	563	545	454	492	–
Total taxa site	8	12	14	17	27	19	22	32	–
EPT families, Small rivers	5	5	6	7	7	7	8	10	9.2
EPT families, Large rivers	6	6	7	9	10	10	9	13	13.3
TT, Small rivers	6	7	8	8	13	11	12	15	19.1
TT, Large rivers	6	10	10	14	16	12	13	21	22.4
PMA, Small rivers	0.295	0.287	0.275	0.142	0.291	0.284	0.338	0.144	0.497
PMA, Large rivers	0.121	0.132	0.217	0.265	0.162	0.112	0.211	0.290	0.549
Shannon index	1.06	1.32	1.87	1.58	0.96	1.47	1.69	1.83	–

Abbreviations of indices, see section 3.4. Sampling sites A–D are indicated in Figure 4. All ecological indices (EPT families, TT and PMA) are shown separately for small clearwater rivers (catchment area < 100 km²) and for large and very large clearwater rivers (catchment area > 10 000 km²). Colours indicate ecological classes: blue = high, green = good, yellow = moderate, light brown = poor, and red = bad. Reference values in last column are Finnish WFD classification values of the two river types. Reference values are averages of streams in a natural state, and they are always higher than the lower limit of high ecological quality (Aroviita et al. 2019).

Aroviita J, Mitikka S, Vienonen S. 2019. Pintavesien tilan luokittelu ja arviointiperusteet vesienhoidon kolmannella kaudella. Suomen Ympäristökeskuksen Raportteja. 37:1–182. (in Finnish). https://helda.helsinki.fi/handle/10138/306745.

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