What is the influence of a reduction of planktivorous and benthivorous fish on water quality in temperate eutrophic lakes? A systematic review

Table 5 Comparison of responsive and unresponsive lakes

	Responsive lakes (significant improvement)			Unresponsive lakes (no significant improvement)
	Mean	95% C.I.	n	Mean	95% C.I.	n
Response: Secchi depth 1–3 years after manipulation (vs. before manipulation)
Lake area (ha)	18	10 – 32	19	40	14 – 119	8
Mean depth (m)	1.7	1.3 – 2.2	19	1.8	1.3 – 2.5	8
Retention time (days)	171	63 – 461	11	409	221 – 754	5
Pre-manipulation TP (μg/l)	144	93 – 223	19	127	62 – 260	6
Mean atmospheric temperature (°C)	8.0	7.0 – 9.0	19	7.8	6.4 – 9.2	8
Duration of main manipulation (yr)	2.1	1.6 – 2.5	19	2.4	1.5 – 3.3	8
Fish removal (kg/ha)	233	160 – 338	18	251	198 – 317	7
Fish removal (kg/ha/yr)	124	84 – 183	18	119	70 – 203	7
Fish stock depletion (%)	56	37 – 76	13	40	17 – 62	5
Response: Chlorophyll a 1–3 years after manipulation (vs. before manipulation)
Lake area (ha)	12	5 – 36	12	35	14 – 86	15
Mean depth (m)	1.3	1.1 – 1.6	11	1.8	1.4 – 2.4	15
Retention time (days)	78	22 – 275	4	210	103 – 428	9
Pre-manipulation TP (μg/l)	196	120 – 322	12	126	83 – 190	13
Mean atmospheric temperature (°C)	8.1	7.1 – 9.1	12	8.2	7.5 – 8.9	15
Duration of main manipulation (yr)	2.0	1.4 – 2.6	12	2.0	1.5 – 2.5	15
Fish removal (kg/ha)	250	149 – 420	11	272	184 – 403	12
Fish removal (kg/ha/yr)	137	74 – 252	11	140	98 – 202	12
Fish stock depletion (%)	78	56 – 99	7	58	42 – 75	12

Data are based on the selected dataset, with stocking-only interventions excluded. Lake areas, mean depths, retention times, pre-manipulation TP concentrations and fish removals were log-transformed before calculation of means and confidence intervals, and then back-transformed.

ISSN: 2047-2382