Spatial version regarding presence really seem to seen hitchhiker species with Yards. alfredi (adult and you may teenager Elizabeth. naucrates) was in fact investigated of the mapping the new part of sightings at each site (classified because of the website mode) where hitchhiker kinds is establish (final number out of sightings where hitchhikers were seen / final amount of sightings at website) into the ArcGIS ten.eight. One sites having all in all, 9 or a lot fewer sightings (213 internet sites) was indeed omitted to minimize the brand new bias the lowest quantity of sightings possess on study.
Temporal variation in the eastmeeteast Birine NasÄ±l Mesaj presence regarding adult and you may juvenile E. naucrates that have Meters. alfredi try investigated playing with month-to-month day series. It collection integrated that time to the most readily useful level of sightings (2008–2019) to incorporate the ideal period from which to help you visualise trends (i.elizabeth., seasonality). The monthly final amount out-of sightings was basically remedied to possess survey work of the figuring the latest suggest monthly number of manta radiation noticed for each and every survey (month-to-month overall manta ray sightings / month-to-month final amount of studies).
Generalised linear combined habits.
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.
A maximum of 4901 Yards. alfredi was directly understood [men = 2442 (50%), women = 2459 (50%)] during all in all, 72912 sightings, of which 44071 (60%) have been of females [adult = 25700 (58%), teenager = 18371 (42%)] and you may 28841 (40%) was indeed guys [adult = 25968 (90%), subadult = 1443 (5%), juvenile = 1430 (5%)]. All of the sightings taken place across 353 sites, where 95 (27%) was basically clean up programs [sightings = 24034 (33%)], 53 (15%) was cruising section [sightings = 129 (0%)], and 205 (58%) giving elements [sightings = 48749 (67%)].