Influence of protected areas on fish assemblages and fisheries in a large tropical river

Abstract

Protected areas are one of the main tools for biological conservation worldwide. Although they have contributed to an increase in fish abundance and alleviated the impacts of fishing on marine ecosystems, the impacts of fishing and of protected areas in freshwater ecosystems are less well known. We compared fishing productivity and fish assemblage descriptors of two distinct protected areas designated for sustainable use of natural resources and an unprotected area in the Tapajós River, in the Brazilian Amazon. Two hypotheses were tested: () fishers from protected areas have higher catch per unit effort than those from unprotected areas; and () fish assemblages in protected areas have higher biomass, abundance, presence of target species, species richness, fish size and mean trophic level than those in unprotected areas. A total of , fish landings were recorded and two surveys were undertaken to sample fishes. Eleven environmental parameters were quantified to distinguish between effects of environmental heterogeneity and protected areas. The catch per unit effort of fishers was higher within protected areas than in unprotected areas, suggesting that protected areas reduce the levels of fishing pressure and increase fishing productivity. However, the fish assemblage descriptors were correlated more with environmental variables than with protected areas, indicating a relatively weak effect of protected areas on fish communities in lakes. The results highlight the importance of considering the influence of environmental heterogeneity in fish conservation programmes, and the positive effect of protected areas on fishing productivity in freshwater environments.

Ecological influences of human population size and distance to urban centres on fish communities in tropical lakes

“…The Negro River has black waters, which have low nutrient levels and acidic pH values, owing to large quantities of dissolved organic matter, such as humic and fulvic compounds (Goulding, Carvalho, & Ferreira, ). More information on the environmental characteristics, fish, and fisheries of each river can be found in previous studies (Begossi, Silvano, & Ramos, ; Keppeler, Hallwass, & Silvano, ; Silva & Begossi, ; Silvano et al, ; Silvano, Ramires, & Zuanon, ).…”

“…Data were analysed from previous studies (Keppeler et al, ; Silvano et al, ; Silvano et al, ), together with original data of 11 158 fish sampled in 48 floodplain lakes, from 2000 to 2013 (Table ). Lakes with fewer than 10 individual fish collected were excluded from the analyses.…”

“…The gillnets were set in the water for a period of 8 to 10 h during the daytime (between 06:00 and 18:00 h), and were checked for fish every 2–4 h. Only samples taken in the low‐water season were analysed, when fish sampling is more efficient owing to an increased fish density in restricted water bodies, resulting in increased catches with gillnets (Silvano, Amaral, & Oyakawa, ). Furthermore, it is precisely during the periods of receding water and low water when fishing boats usually increase the fishing effort in floodplain lakes (Keppeler et al, ). Gillnet sampling usually catches mostly open water or demersal fish, which include most or all fish regularly exploited by fisheries.…”

The Effects of Regulated Area Location and Size on the Effectiveness of a Catch‐and‐Release Season for a Riverine Black Bass

“…; Keppeler et al. ). Most closed areas are enacted during specific seasons at large geographical scales, such as states or provinces, presumably based upon prior knowledge or opinion regarding periods of vulnerability of these fish to angling harvest (Quinn ).…”

“…Because a key objective for most APAs is to provide refugia for spawning fish from harvest (Jennings 2001;Loury et al 2017), closed areas function in a similar way to APAs. Empirical data have rarely been used in the planning process of either APAs or closed areas (Botsford et al 2003;Halpern 2003), and their effectiveness has been widely variable (Cote et al 2001;Kubacki et al 2002;Quinn 2002;Claudet et al 2008;Vandeperre et al 2011;Keppeler et al 2017). Most closed areas are enacted during specific seasons at large geographical scales, such as states or provinces, presumably based upon prior knowledge or opinion regarding periods of vulnerability of these fish to angling harvest (Quinn 2002).…”