Spatial version regarding presence of the most extremely seem to observed hitchhiker species that have Meters. alfredi (mature and teenager Age. naucrates) were investigated by the mapping the newest portion of sightings at each webpages (categorized by webpages function) where in actuality the hitchhiker species is actually present (final amount from sightings in which hitchhikers was seen / total number of sightings at the web site) for the ArcGIS 10.seven. One sites with all in all, 9 or fewer sightings (213 sites) had been excluded to minimize the brand new bias a decreased number of sightings could have toward investigation.
Temporary version regarding presence off adult and you may juvenile Elizabeth. naucrates with Yards. alfredi was examined using month-to-month big date show. This show integrated the period to your best amount of sightings (2008–2019) to include the right months of which in order to visualise styles (we.age., seasonality). The fresh monthly final amount off sightings was basically remedied to own survey effort by the calculating this new mean monthly level of manta light seen for every single questionnaire (month-to-month full manta ray sightings / month-to-month final amount out of surveys).
Generalised linear mixed patterns.
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 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.
Abilities
A total of 4901 Yards. alfredi was basically truly understood [men = 2442 (50%), lady = 2459 (50%)] during the all in all, 72912 sightings, where 44071 (60%) had been of women [mature = 25700 (58%), teenager = 18371 (42%)] and you may 28841 (40%) have been males [adult = 25968 (90%), subadult = 1443 (5%), juvenile = 1430 (5%)]. All of the sightings taken place all over 353 sites, from which 95 (27%) was indeed cleanup station [sightings = 24034 (33%)], 53 (15%) have been cruising components [sightings = 129 (0%)], and you will 205 (58%) eating components [sightings = 48749 (67%)].