Spatial type from the visibility of the very most apparently observed hitchhiker species which have M. alfredi (mature and you will juvenile E. naucrates) was basically investigated by mapping new percentage of sightings at every webpages (labeled from the web site means) where in actuality the hitchhiker types is present (total number out-of sightings in which hitchhikers have been noticed / total number off sightings at web site) within the ArcGIS 10.7. People sites which have a total of 9 otherwise a lot fewer sightings (213 web sites) were omitted to reduce the prejudice a decreased amount of sightings might have on investigation.
Temporary version regarding exposure from adult and you may teenager E. naucrates that have Meters. alfredi is actually investigated having fun with month-to-month day series. This series included the period towards the top number of sightings (2008–2019) to add an appropriate several months from which so you can visualise trend (i.e., seasonality). New monthly final amount regarding sightings had been fixed having survey energy from the calculating new suggest month-to-month level of manta rays observed for each questionnaire (monthly total manta ray sightings / single Sex Sites dating month-to-month final number of studies).
Generalised linear blended 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 0.05 are not reported.
Efficiency
All in all, 4901 M. alfredi was basically yourself understood [men = 2442 (50%), women = 2459 (50%)] during the a total of 72912 sightings, at which 44071 (60%) was of women [adult = 25700 (58%), teenager = 18371 (42%)] and you will 28841 (40%) was boys [mature = 25968 (90%), subadult = 1443 (5%), juvenile = 1430 (5%)]. Every sightings occurred all over 353 sites, at which 95 (27%) was indeed clean up stations [sightings = 24034 (33%)], 53 (15%) was basically driving portion [sightings = 129 (0%)], and you can 205 (58%) feeding areas [sightings = 48749 (67%)].
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