Dear Colleagues On behalf of my co-authors, I am pleased to share the following open-access publications on bottlenose dolphin abundance and movements:
D. Silva, R.F. Young, A. Lavin, C. O’Shea and E. Murray. 2020. Abundance and seasonal distribution of the Southern North Carolina Estuarine System Stock of common bottlenose dolphins (Tursiops truncatus). J. Cetacean Res. Manage. 21: 33-43, available at https://archive.iwc.int/?r=13023<https://nam03.safelinks.protection.outlook.com/?url=https%3A%2F%2Farchive.iwc.int%2F%3Fr%3D13023&data=02%7C01%7Cdcsilva%40coastal.edu%7C94d5a596ae154d9433ef08d7d4cb43b3%7Cbf1f856b8ef84e52be9387d3c3622797%7C0%7C0%7C637211842244326647&sdata=p6bL7DMJ72MmIZK7FPcMqHuqM79bO62RV00OHi9pC24%3D&reserved=0> ABSTRACT Under the US Marine Mammal Protection Act, common bottlenose dolphins along the United States Atlantic coast are managed as a series of 17 distinct stocks. To determine the status of each stock, the Potential Biological Removal (PBR) is compared with anthropogenic removals, primarily as a result of fisheries bycatch. Estimates of abundance, with associated measures of variance, are required to generate the PBR for each stock. The objectives of the current study were to estimate abundance for the Southern North Carolina Estuarine System Stock (SNCESS) of common bottlenose dolphins and to better define the southern boundary of this stock. To meet these objectives, photo-identification surveys were conducted during the summer and winter of 2014 in estuarine and nearshore coastal waters in southern North Carolina. The surveys extended 25km South of the defined southern stock boundary, along the northern South Carolina coast. One mark and one recapture survey were conducted for each season. Each survey was completed in four or five days and covered over 300km of survey tracklines. Dorsal fin images were processed and managed using FinBase, and only images of suitable quality and distinctiveness were used for estimates of abundance. A three-step decision tree was used to assign each dolphin group to either the SNCESS or an adjacent coastal stock, based on sighting location, ranging patterns derived from matches to photo-identification catalogues and statistical modelling. Only sightings classified as SNCESS were used to estimate stock abundance. Abundance estimates were calculated using three approaches: the Chapman modification to the Lincoln-Petersen method, package Rcapture in program R and program MARK 6.2. The most parsimonious approach was the Chapman LP method yielding an estimate of 272 dolphins (95% CI 189–390, CV = 0.32) in the summer of 2014. The distribution of SNCESS dolphins shifted South in the winter and several individuals were observed up to 70km southwest of the currently recognised southern boundary. The results of this study support the current definition of the SNCESS but suggest revisions to the southern boundary. The SNCESS is the smallest bottlenose dolphin stock off the East coast of the USA and is at risk of population decline as a result of fisheries-related mortality. D. Silva, B. Tramutolo, E. DeSalvio, T. Speakman and R. Young (2019). Abundance and Movements of the Northern South Carolina Estuarine System Stock of Bottlenose Dolphins (Tursiops truncatus) (USA). JMATE 11(1): 8-18, available at http://www.oers.ca/journal/volume11/issue1/scientific.pdf<https://nam03.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.oers.ca%2Fjournal%2Fvolume11%2Fissue1%2Fscientific.pdf&data=02%7C01%7Cdcsilva%40coastal.edu%7C4b4df979434441e658a608d7493c793f%7Cbf1f856b8ef84e52be9387d3c3622797%7C0%7C1%7C637058396402112235&sdata=E2W4uCjM0KLThNGEnfh%2F3nshxPubugfsxEVFR9dREhM%3D&reserved=0> ABSTRACT In the USA, federal law requires managing anthropogenic threats to bottlenose dolphins at the stock level. The Northern South Carolina Estuarine System Stock (NSCESS) lacks estimates of abundance and potential biological removal required for management. Moreover, the southern stock boundary of the NSCESS is shared with the northern boundary for the Charleston Estuarine System Stock (CESS). The goals of this study were to investigate the empirical location of the southern stock boundary and to generate the first estimate of abundance for the NSCESS. Mark-recapture photo-identification surveys including one ‘mark’ and two ‘recapture’ sessions were completed between August and early October 2016. Predefined survey tracks approximately 245 km in length covered the described range for the NSCESS and an additional 11 km southwest of the currently defined southern stock boundary. Long term movement patterns were also investigated via comparison with historical catalogs from the NSCESS and CESS regions. Observed movement patterns did not suggest a clear revision to the southern stock boundary, thus sightings within the defined NSCESS stock boundaries were used to estimate abundance. Dorsal fin photographs were scored for suitable quality and distinctiveness using the program FinBase, and stock abundance was estimated with closed population models using the package Rcapture for program R. The best fitted model, Mth, was selected based on the lowest AIC value and yielded an abundance estimate of 453 dolphins (95% CI = 265-773, CV = 0.28). This study contributes to the sustainable management of the NSCESS and informed response to anthropogenic and natural threats. Best regards, Dani Silva
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