Reef manta beam (Meters. alfredi) sightings and relevant hitchhiker species (1987–2019)

Spatial adaptation throughout the exposure of the very most appear to observed hitchhiker types having Yards. alfredi (mature and teenager Elizabeth. naucrates) was investigated from the mapping the percentage of sightings at every web site (labeled of the website mode) where the hitchhiker types try expose (final amount out of sightings where hitchhikers was basically noticed / final amount from sightings from the webpages) in the ArcGIS ten.eight. One sites having a maximum of 9 otherwise a lot fewer sightings (213 internet) was in fact omitted to minimize the fresh prejudice the lowest amount of sightings might have on the studies.

Temporal variation on the presence away from adult and you may juvenile Age. naucrates which have Meters. alfredi is examined using monthly date series. This series integrated that point for the top number of sightings (2008–2019) to add the ideal period at which in order to visualise trend (i.age., seasonality). The brand new monthly final number regarding sightings was basically fixed having questionnaire efforts of the figuring the latest indicate month-to-month amount of manta light noticed for each questionnaire (monthly total manta beam sightings / month-to-month total number out of surveys).

Generalised linear blended models.

Logistic generalised linear mixed models (GLMM) using R v4.0.0 were used to investigate relationships between the presence of the most frequently observed hitchhiker species (adult and juvenile E. naucrates, G. speciosus, and Lutjanus bohar) with M. alfredi and four explanatory variables: sex with pregnancy status, maturity status, site function (determined by the predominant behaviour observed at the site ), and seasonality (NE or SW Monsoon). Due to the low number of recorded associations between M. alfredi and most of the hitchhiker species, only those with sufficient data were included in the GLMM analysis. The same model was used for Remora remora (the most frequently observed hitchhiker species with M. birostris), but without site function, and sex was classified only as male or female as pregnancies were only observed during four sightings. Each GLMM was fitted with a logit link function to the binary response of hitchhiker species presence (1) and absence (0) using the ‘lme4′ R package . Each model contained the manta-ID as a random intercept to account for any temporal autocorrelation arising from individual rays being repeatedly observed . To compare the relative goodness-of-fit, GLMM models without random effects (GLM) were tested. To reliably estimate the parameters, categories of variables with levels observed equal to or less than five times were removed. For example, under the category behavioural activity, the level ‘breaching’ was observed on less than five occasions, so LGBT dating site was removed from analysis. The most informative explanatory variables were identified by firstly testing GLMM models with all combinations of explanatory variables. The variance inflation factor (VIF) was used to test models for multicollinearity; the maximum VIF was <1.5. Model performance was assessed using corrected Akaike information criterion (AICc) test statistic using the ‘MuMin' R package , and the DHARMa R package was used to check the model residuals were normally distributed. The highest-ranking models (with the lowest AICc value, S1 Table) for each hitchhiker species were then interpreted in terms of odds ratios (ORs) (the likelihood of the presence of the hitchhiker species in comparison with the reference category). Any models with ?AICc <2 were considered in interpretation of the highest-ranking model . The significance of each explanatory variable was determined by the 95% confidence interval (CI) of OR, whereby a narrower CI indicates a more precise estimation while, in comparison, a wider CI which had a greater uncertainty. A CI that crossed one is considered non-significant. Any ORs with p > 0.05 are not reported.


All in all, 4901 M. alfredi were myself known [men = 2442 (50%), females = 2459 (50%)] during the a maximum of 72912 sightings, where 44071 (60%) was of women [mature = 25700 (58%), juvenile = 18371 (42%)] and you can 28841 (40%) was indeed men [adult = 25968 (90%), subadult = 1443 (5%), juvenile = 1430 (5%)]. Every sightings occurred around the 353 internet sites, at which 95 (27%) was in fact cleaning programs [sightings = 24034 (33%)], 53 (15%) was basically touring components [sightings = 129 (0%)], and you can 205 (58%) eating portion [sightings = 48749 (67%)].

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