Comparing fishers’ and scientific estimates of size at maturity and maximum body size as indicators for overfishing

Abstract

We tested whether fishers' local ecological knowledge (LEK) of two fish life-history parameters, size at maturity (SAM) at maximum body size (MS), was comparable to scientific estimates (SEK) of the same parameters, and whether LEK influenced fishers' perceptions of sustainability. Local ecological knowledge was documented for 82 fishers from a small-scale fishery in Samaná Bay, Dominican Republic, whereas SEK was compiled from the scientific literature. Size at maturity estimates derived from LEK and SEK overlapped for most of the 15 commonly harvested species (10 of 15). In contrast, fishers' maximum size estimates were usually lower than (eight species), or overlapped with (five species) scientific estimates. Fishers' size-based estimates of catch composition indicate greater potential for overfishing than estimates based on SEK. Fishers' estimates of size at capture relative to size at maturity suggest routine inclusion of juveniles in the catch (9 of 15 species), and fishers' estimates suggest that harvested fish are substantially smaller than maximum body size for most species (11 of 15 species). Scientific estimates also suggest that harvested fish are generally smaller than maximum body size (13 of 15), but suggest that the catch is dominated by adults for most species (9 of 15 species), and that juveniles are present in the catch for fewer species (6 of 15). Most Samaná fishers characterized the current state of their fishery as poor (73%) and as having changed for the worse over the past 20 yr (60%). Fishers stated that concern about overfishing, catching small fish, and catching immature fish contributed to these perceptions, indicating a possible influence of catch-size composition on their perceptions. Future work should test this link more explicitly because we found no evidence that the minority of fishers with more positive perceptions of their fishery reported systematically different estimates of catch-size composition than those with the more negative majority view. Although fishers' and scientific estimates of size at maturity and maximum size parameters sometimes differed, the fact that fishers make routine quantitative assessments of maturity and body size suggests potential for future collaborative monitoring efforts to generate estimates usable by scientists and meaningful to fishers.

Ethnozoological knowledge of traditional fishing villages about the anadromous sea lamprey (Petromyzon marinus) in the Minho river, Portugal

“…This threatened and valuable fishing village knowledge of intricate biological patterns should encourage researchers and managers to begin considering, evaluating, and integrating this data source as a means of improving local fishery resource management [83]. Even in situations where fisher’s scientific parameters and estimates are different at specific points, the mere fact that they make regular informal diagnoses motivates an eminent faculty to introduce these individuals into ancillary conservation efforts to generate useful estimates [86].…”

Identifying potential causes of fish declines through local ecological knowledge of fishers in the Ganga River, eastern Bihar, India

“…A linear regression analysis was run between the natural logarithms of Wmax_LEK and Wmax_FB for all species. The magnitude and sign of the linear model slope were interpreted as potential indicators of responses to overfishing for each species through possible size reduction (based on McLean & Forrester, ). Species that fell below a hypothetical 1:1 line on the plot could be overfished (Wmax_LEK < Wmax_FB) and those above the line not overfished (Wmax_LEK ≥ Wmax_FB).…”

New insights into the recent collapse of Eastern Baltic cod from historical data on stock health

“…In this paper, we assemble historical information to extend the time series of a range of life history and demographic parameters of the EBC, which represent aspects of population health [ 28 , 30 , 31 ]. Historical perspectives have in many cases provided valuable insights regarding baselines and targets for management and conservation of marine life [ 32 – 34 ].…”

“…These biological parameters, which are indicators of population health, need to be considered alongside the biomass and fishing pressure for policies aiming to promote ecosystem based management, such as the Marine Strategy Framework Directive in Europe [29]. In this paper, we assemble historical information to extend the time series of a range of life history and demographic parameters of the EBC, which represent aspects of population health [28,30,31]. Historical perspectives have in many cases provided valuable insights regarding baselines and targets for management and conservation of marine life [32][33][34].…”