Spatial version on presence of the very apparently noticed hitchhiker variety which have Meters. alfredi (adult and you will juvenile Age. naucrates) was basically examined by mapping the brand new portion of sightings at every website (grouped by web site function) the spot where the hitchhiker kinds try introduce (final amount off sightings where hitchhikers have been noticed / sugar baby site Tucson Arizona total number off sightings at webpages) for the ArcGIS 10.7. People internet sites which have a total of nine or fewer sightings (213 internet) were excluded to reduce brand new prejudice the lowest number of sightings could have into the investigation.
Temporary type on exposure out of adult and teenager E. naucrates having Yards. alfredi was examined having fun with monthly day show. This series included the period towards finest level of sightings (2008–2019) to provide a suitable months at which so you can visualise styles (i.e., seasonality). The newest monthly total number out-of sightings had been corrected to own survey work by calculating the fresh indicate monthly amount of manta radiation observed for each survey (month-to-month overall manta beam sightings / month-to-month total number of surveys).
Generalised linear combined activities.
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.
All in all, 4901 M. alfredi was really understood [men = 2442 (50%), girls = 2459 (50%)] while in the a total of 72912 sightings, at which 44071 (60%) was basically of women [adult = 25700 (58%), teenager = 18371 (42%)] and 28841 (40%) have been men [mature = 25968 (90%), subadult = 1443 (5%), juvenile = 1430 (5%)]. Every sightings occurred across the 353 sites, from which 95 (27%) was basically clean programs [sightings = 24034 (33%)], 53 (15%) was in fact driving section [sightings = 129 (0%)], and 205 (58%) feeding components [sightings = 48749 (67%)].