Risso's dolphins (Grampus griseus) in a proposed Marine Protected Area off east Lewis (Scotland, UK), 2010–2017

AbstractThe coastal waters of east Lewis from the Butt of Lewis to Loch Erisort are a proposed Marine Protected Area (MPA) for Risso's dolphins (Grampus griseus). A total of 100.4 h (2006.4 km) of active search effort (Beaufort sea states ≤3) was collected during 72 dedicated boat surveys between 2010 and 2017 (primarily in August and September) in the southern part of the MPA and south to the Shiant Isles. Forty Risso's dolphin sightings and 24.1 h of encounter effort were recorded, predominantly along the southern and eastern Eye Peninsula in 20–40 m water depths and at distances <1 km from shore. Group size ranged from one to 50 animals (mean = 11.8 dolphins) and calves occurred in 37.5% of sightings. A total of 2404 shore-based scans (Beaufort sea states ≤3) carried out from Tiumpan Head between September 2011 and December 2017 resulted in 271 (11.3%) ‘dolphin-present’ scans. Dolphins were present year-round, with a seasonal increase between May and October. ‘Calf-present’ scans only occurred between April and October. Photo-identification images from 28 boat surveys produced a minimum population size of 117 animals. There was evidence of high inter- and intra-annual site fidelity, with individual dolphins photographically captured in up to six of the eight survey years, and between two and seven capture dates being recorded for over 45% of individuals within most years. The combined datasets support the importance of east Lewis for Risso's dolphins, and recommendations are made for ongoing monitoring of dolphin occurrence throughout the wider MPA.

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Using complementary visual approaches to investigate residency, site fidelity and movement patterns of the dusky grouper (Epinephelus marginatus) in a Mediterranean marine protected area

Marine Biology ◽

10.1007/s00227-021-03917-9 ◽

2021 ◽

Vol 168 (7) ◽

Author(s):

Elena Desiderà ◽

Egidio Trainito ◽

Augusto Navone ◽

Rémi Blandin ◽

Luana Magnani ◽

...

Keyword(s):

Protected Area ◽

Site Fidelity ◽

Marine Protected Area ◽

Small Scale ◽

Underwater Visual Census ◽

Entire Area ◽

Photo Identification ◽

Dusky Grouper ◽

Spatio Temporal ◽

Study Sites

AbstractAssessing individuals’ abundance, residency (presence at a site within a certain period) and site fidelity (tendency to return to the same site in subsequent seasons or years) is crucial for evaluating and improving the effectiveness of spatial conservation/management measures regarding ecologically and socio-economically valuable species. Using underwater visual census (UVC) and photo-identification (photo-ID) techniques, we estimated the abundance, residency and site fidelity of the dusky grouper, Epinephelus marginatus, at two protected sites within the Tavolara-Punta Coda Cavallo Marine Protected Area (Sardinia, Italy) in the summers of 2017–2018. The scope and spatio-temporal resolution of the study was extended by involving volunteer recreational divers in the photo collection. Grouper mean densities varied significantly across sampling dates, with a significant variability between the 2 years and the two investigated sites. At least 94 grouper visited the study sites in the summers of 2017–2018 based on the analysis of 968 high-quality photos using a semi-automated software to photo-identify individuals. Overall, the most frequently sighted grouper was recorded on 32 different days and 21 individuals (22%) identified in 2017 were re-sighted in 2018. The participation of volunteer recreational divers helped detect the inter-site (3.5–4 km apart) movements of a female and a male, supporting previous findings regarding the occurrence of reproduction-related movements. This study provides novel insights into the residency and site-fidelity patterns of the dusky grouper, and its small-scale movements probably related to reproduction. Specifically, we provide indications that effective protection from fishing should encompass the entire area used by grouper for reproductive movements.

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Capitoline Dolphins: Residency Patterns and Abundance Estimate of Tursiops truncatus at the Tiber River Estuary (Mediterranean Sea)

Biology ◽

10.3390/biology10040275 ◽

2021 ◽

Vol 10 (4) ◽

pp. 275

Author(s):

Daniela Silvia Pace ◽

Chiara Di Marco ◽

Giancarlo Giacomini ◽

Sara Ferri ◽

Margherita Silvestri ◽

...

Keyword(s):

Population Size ◽

Tursiops Truncatus ◽

Site Fidelity ◽

Bottlenose Dolphins ◽

River Estuary ◽

Suitable Habitat ◽

Tyrrhenian Sea ◽

Abundance Estimate ◽

Photo Identification ◽

Tiber River

Periodic assessments of population status and trends to detect natural influences and human effects on coastal dolphin are often limited by lack of baseline information. Here, we investigated for the first time the site-fidelity patterns and estimated the population size of bottlenose dolphins (Tursiops truncatus) at the Tiber River estuary (central Mediterranean, Tyrrhenian Sea, Rome, Italy) between 2017 and 2020. We used photo-identification data and site-fidelity metrics to study the tendency of dolphins to remain in, or return to, the study area, and capture–recapture models to estimate the population abundance. In all, 347 unique individuals were identified. The hierarchical cluster analysis highlighted 3 clusters, labeled resident (individuals encountered at least five times, in three different months, over three distinct years; n = 42), part-time (individuals encountered at least on two occasions in a month, in at least two different years; n = 73), and transient (individuals encountered on more than one occasion, in more than 1 month, none of them in more than 1 year; n = 232), each characterized by site-fidelity metrics. Open POPAN modeling estimated a population size of 529 individuals (95% CI: 456–614), showing that the Capitoline (Roman) coastal area and nearby regions surrounding the Tiber River estuary represent an important, suitable habitat for bottlenose dolphins, despite their proximity to one of the major urban centers in the world (the city of Rome). Given the high number of individuals in the area and the presence of resident individuals with strong site fidelity, we suggest that conservation plans should not be focused only close to the Tiber River mouths but extended to cover a broader scale of area.

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Brachioteuthis beanii Verrill, 1881 (Cephalopoda: Brachioteuthidae) in the northwest Atlantic

Bulletin of Marine Science ◽

10.5343/bms.2019.0073 ◽

2020 ◽

Vol 96 (2) ◽

pp. 309-322

Author(s):

Elizabeth K Shea ◽

Judy Stadler ◽

Annie Lindgren

Keyword(s):

Nova Scotia ◽

Food Web ◽

Population Size ◽

Size Distribution ◽

Protected Area ◽

Marine Protected Area ◽

Measurement Data ◽

Spawning Aggregation ◽

Males And Females ◽

External Ornamentation

Four research cruises to the Gully Marine Protected Area (known as "the Gully") off Nova Scotia, Canada (2007–2010) collected 1454 specimens of the oegopsid squid family Brachioteuthidae. All specimens were identified as Brachioteuthis beanii, and the 842 individuals collected in 2007 were used to describe the morphology and ecology of the species. A subset of 565 specimens were measured for population size distribution, and over 200 of these individuals (21–117 mm ML) were fixed, vouchered, measured, dissected, and sexed to examine the internal and external characters of juveniles, males, and females. Specimens <40 mm ML were almost entirely juveniles. Specimens 40–49 mm ML were a mix of juveniles, males, and females. The smallest specimens, where the spermatophoric complex and nidamental glands could be identified, were approximately 39 mm ML in both males and females, suggesting that maturation begins at roughly the same size in both sexes. Specimens >50 mm ML could be sexed based solely on the color and texture of the mantle. Male mantles were fusiform in shape with few small, widely spaced chromatophores and a reticulated net on the mantle that developed concurrent with the internal spermatophoric complex. Females had a flaccid mantle with larger and denser chromatophores on the mantle and head and no external ornamentation (i.e., ridges or nodules). Measurement data showed that males had slightly larger arms and wider fins than females. The high abundance of B. beanii at the Gully in August/September may be a spawning aggregation and suggests that this small squid is an important component of the canyon food web.

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Population size and survivorship for juvenile lemon sharks (Negaprion brevirostris) on their nursery grounds at a marine protected area in Brazil

Neotropical Ichthyology ◽

10.1590/s1679-62252009000200011 ◽

2009 ◽

Vol 7 (2) ◽

pp. 205-212 ◽

Cited By ~ 11

Author(s):

Renato Hajenius Aché de Freitas ◽

Ricardo S. Rosa ◽

Bradley M. Wetherbee ◽

Samuel H. Gruber

Keyword(s):

Population Size ◽

Protected Area ◽

Marine Protected Area ◽

Survival Rates ◽

Direct Methods ◽

Nursery Grounds ◽

Negaprion Brevirostris ◽

Animal Populations ◽

Population Size Estimates ◽

Lemon Sharks

Sharks face a number of obstacles for surviving their first several years of life and many species occupy nursery areas. Although estimates of survival, particularly for young age classes, are essential for assessing, monitoring and effectively managing animal populations, there have been relatively few calculations of survival within shark populations and even fewer estimates based on direct methods for sharks on their nursery grounds. We used tag-recapture methods to estimate the population size and survival of juvenile lemon sharks (Negaprion brevirostris) on their nursery grounds at Atol das Rocas, a marine protected area in Brazil. Sharks were sampled from1999 to 2003. Population size estimates ranged from 12 to 100 juvenile sharks and survival estimates ranged between 24-54% with a mean of 44.6% over the most robust sampling periods. The population of juvenile lemon sharks declined over the course of our study, whereas survival rates may have increased over the same time period. Even a modest level of fishing and removal of mature females in adjacent areas may dramatically affect small populations of sharks within a small and isolated nursery such as Atol das Rocas. The lower survival rates and population size at Atol das Rocas could be the result of differences in physical characteristics of this nursery in comparison to others used by lemon sharks in the northwestern Atlantic. Such comparatively lower populational parameters suggest that the population of young lemon sharks is fragile at the Atol das Rocas nursery.

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Site Fidelity and Residency of Tursiops truncatus off the Aragua Coast, Venezuela-First Records of Long Residency

Journal of Marine Science ◽

10.30564/jms.v3i4.3811 ◽

2021 ◽

Vol 3 (4) ◽

Author(s):

S. Cobarrubia-Russo ◽

Sawyer I. ◽

M. Gómez-Alceste ◽

A. Molero-Lizarraga

Keyword(s):

Bottlenose Dolphin ◽

Marine Mammals ◽

Site Fidelity ◽

Marine Protected Area ◽

Extended Period ◽

Comprehensive Analysis ◽

Agglomerative Hierarchical Clustering ◽

Photo Identification ◽

Whale Sharks ◽

First Time

This study represents the first comprehensive analysis of the residency patterns of a coastal population of bottlenose dolphin off the coast of Aragua, Venezuela, over a multi-year period. Using photo-identification, the most recent study (2019-2020) identified 56 individuals with the time between encounters from one to 344 days between the first and last sighting. Site Fidelity (SF) and Residence (RES) indices were calculated and Agglomerative Hierarchical Clustering (AHC) modeling was performed, with three patterns of residence obtained: resident (25%), semiresident (17.86%) and transient (57.14%). These results were contrasted with remodeled data from a previous study (2006-2007), showing similar patterns: resident (24.44%), semi-resident (28.89%) and transient (46.67%). Importantly, two individuals were found to have been resident over the extended period. A breeding female sighted for the first time in 2004 and again in 2020 (16 years) and the other from 2005 to 2020 (15 years). This region is an important area for marine mammals, known to support a resident reproductive population over many years, as well seabirds, sea turtles, whale sharks and fishermen. We recommend that consideration be given to designating the waters as a Marine Protected Area to safeguard the existing population and provide benefit to the surrounding marine environment.

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