Engaging recreational scuba divers in marine citizen science: Differences according to popularity of the diving area

1. Characterizing the composition of divers visiting different diving areas could help to design marine citizen science (MCS) projects that support biodiversity monitoring and marine conservation.
2. Recreational scuba divers mostly prefer warm and clear waters with coral reefs, and based on the Duffus and Dearden’s wildlife tourism framework we hypothesized that a more popular diving area is visited mostly by generalist divers, whereas in a less popular diving area a higher proportion of specialist divers would be found.
3. Recreational scuba divers were surveyed in diving centres at two diving areas, Rapa Nui (more popular, with warm and clear coral-reef waters) and the Chilean mainland (less popular, with productive and temperate–cold waters), to determine their diving profile, visiting profile, marine species knowledge, and interest and participation in MCS.
4. Support for our hypothesis (generalist divers on Rapa Nui and specialist divers on the mainland) was weak, but recreational divers on Rapa Nui were mostly foreign visitors who come for single visits, whereas divers from the mainland were predominantly Chileans who return repeatedly to the diving area. In both diving areas the divers expressed a strong interest to be trained and to participate in MCS, but divers from Rapa Nui were interested in brief pre-dive inductions, whereas divers from the Chilean mainland preferred intensive training courses.
5. Based on these findings we recommend specific MCS strategies for divers in both types of areas, e.g. simple protocols in more popular diving areas, with short pre-dive briefings for divers, and medium or long-term programmes in areas where most divers are local with high return rates. In these latter conditions more extensive training will be useful, which allows divers to gain more experience and assume higher responsibilities within an MCS project.

     

Impacts of parasites on marine survival of Atlantic salmon: a meta‐analysis

Parasites can, in theory, have large impacts on the survival of fish populations. One method to evaluate such impacts on anadromous species is to apply manipulative field experiments in which parallel groups of antiparasitically treated and non‐treated fish are simultaneously released and then subsequently recaptured as returning adults. A systematic review and meta‐analysis on all such Norwegian studies on Salmo salar provided a data set for the time period 1996 to 2011 on 118 release groups comprising 657 624 fish released and 3989 recaptured. The overall risk ratio (RR) was estimated to be 1.18 (95% CI: 1.07–1.30). The effect varied strongly between groups, (Higgins I² = 40.1%). Over 70% of this heterogeneity could be explained by the release location, time period and baseline survival. The most important predictor variable was baseline survival. In groups with low recapture in the control group (low baseline survival), the effect of treatment was high (RR = 1.7), while in groups with high recapture in the control group (high baseline survival), there was no effect of treatment (RR ~ 1.00). The most prevalent parasite in the region affected by the drugs administered was Lepeophtheirus salmonis. Hence, the meta‐analysis supports the hypothesis that L. salmonis contributes to the mortality of S. salar during outward migration. However, the effect of treatment was not consistent, but was evidently strongly modulated by other risk factors. The results suggest that the population‐level effects of parasites cannot be estimated independently of other factors affecting the marine survival of S. salar.