Reef manta ray (Meters. alfredi) sightings and you can associated hitchhiker variety (1987–2019)

Reef manta ray (Meters. alfredi) sightings and you can associated hitchhiker variety (1987–2019)

Spatial variation in the exposure quite seem to noticed hitchhiker varieties which have Yards. alfredi (adult and teenager Age. naucrates) had been examined because of the mapping brand new portion of sightings at every webpages (categorized by the web site form) where in actuality the hitchhiker kinds are expose (final number out-of sightings in which hitchhikers was observed / total number from sightings at website) inside ArcGIS One web sites having a total of nine or less sightings (213 internet sites) was in fact excluded to attenuate the brand new prejudice a reduced quantity of sightings could have on investigation.

Temporal adaptation on presence of adult and you may teenager E. naucrates having Yards. alfredi is examined using month-to-month time collection. So it series incorporated that point with the better quantity of sightings (2008–2019) to add the right months from which so you’re able to visualise trends (i.elizabeth., seasonality). New monthly total number regarding sightings was fixed getting survey work by the figuring the latest indicate month-to-month number of manta rays noticed for every single questionnaire (monthly overall manta ray sightings / monthly final amount from studies).

Generalised linear blended 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) best hookup apps Chattanooga 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 were directly known [male = 2442 (50%), females = 2459 (50%)] through the a total of 72912 sightings, where 44071 (60%) was indeed of females [mature = 25700 (58%), teenager = 18371 (42%)] and you can 28841 (40%) was basically people [adult = 25968 (90%), subadult = 1443 (5%), juvenile = 1430 (5%)]. Every sightings taken place round the 353 sites, of which 95 (27%) was in fact cleanup stations [sightings = 24034 (33%)], 53 (15%) were driving components [sightings = 129 (0%)], and you will 205 (58%) eating areas [sightings = 48749 (67%)].


0 Comments Add comment

Leave a comment