scholarly journals Survival Rates and Capture Heterogeneity of Bottlenose Dolphins (Tursiops truncatus) in the Shannon Estuary, Ireland

2021 ◽  
Vol 8 ◽  
Author(s):  
Kim E. Ludwig ◽  
Mags Daly ◽  
Stephanie Levesque ◽  
Simon D. Berrow
Keyword(s):  
Range Expansion ◽  
Bottlenose Dolphin ◽  
Site Fidelity ◽  
Bottlenose Dolphins ◽  
Survival Rates ◽  
Adult Survival ◽  
Demographic Parameter ◽  
Resident Population ◽  
The Mean ◽  
Survey Effort

Adult survival is arguably the most important demographic parameter for long-lived species as it has a large impact on population growth, and it can be estimated for cetacean populations using natural markings and mark-recapture (MR) modelling. Here we describe a 26-year study of a genetically discrete, resident population of bottlenose dolphins in the Shannon Estuary, Ireland, conducted by an NGO using multiple platforms. We estimated survival rates (SRs) using Cormack-Jolly-Seber models and explored the effects of variable survey effort, multiple researchers, and changes in camera equipment as well as capture heterogeneity induced by changes in marks and site fidelity variation, all common issues affecting longitudinal dolphin studies. The mean adult SR was 0.94 (±0.001 SD) and thus comparable to the estimates reported for other bottlenose dolphin populations. Capture heterogeneity through variation in mark severity was confirmed, with higher capture probabilities for well-marked individuals than for poorly marked individuals and a “transience” effect being detected for less well-marked individuals with 43% only recorded once. Likewise, both SR and capture probabilities were comparatively low for individuals with low site fidelity to the Shannon Estuary, and SR of these individuals additionally decreased even further toward the end of the study, reflecting a terminal bias. This bias was attributed to non-random temporal migration, and, together with high encounter rates in Brandon Bay, supported the hypothesis of range expansion. Our results highlight the importance of consistent and geographically homogenous survey effort and support the differentiation of individuals according to their distinctiveness to avoid biased survival estimates.

Individual movements between local coastal populations of bottlenose dolphins (Tursiops truncatus) in the northern and eastern Black Sea

2016 ◽  
Vol 98 (2) ◽  
pp. 223-229 ◽  
Author(s):  
Elena Gladilina ◽  
Olga Shpak ◽  
Valentin Serbin ◽  
Anna Kryukova ◽  
Dmitry Glazov ◽  
...  
Keyword(s):  
Black Sea ◽  
Bottlenose Dolphin ◽  
Tursiops Truncatus ◽  
Site Fidelity ◽  
Bottlenose Dolphins ◽  
The Black Sea ◽  
Small Range ◽  
Short Term ◽  
High Population Growth ◽  
Physical Barriers

The Black Sea subspecies of the bottlenose dolphin (Tursiops truncatus ponticus) is threatened and has a small range. Its population structure is little known: it possibly includes a few local coastal populations. We assessed connectivity between coastal groupings in six localities along 800 km of the coastline based on records of photo-identified animals between 2004 and 2014. Abundance of these groupings, as estimated, ranged between 76 and 174 individually distinctive dolphins. In total, there were 350 identified individuals, of which 91 (26%) were resighted within the same areas. However, only three cases of individual movements between local coastal populations were recorded at the distances between 135 and 325 km. Therefore, despite the absence of physical barriers, the coastal Black Sea population is fragmented into numerous resident or locally migrating groupings with site fidelity. These local populations are loosely connected to each other with rare movements between them. This fragmentation can be a factor contributing to short-term fluctuations in abundance of Black Sea bottlenose dolphins and their decline in some localities, despite the potentially high population growth rate.

Inshore and offshore bottlenose dolphin (Tursiops truncatus) communities distinguished by association patterns near Grand Bahama Island, Bahamas

1999 ◽  
Vol 77 (4) ◽  
pp. 581-592 ◽  
Author(s):  
Kelly A Rossbach ◽  
Denise L Herzing
Keyword(s):  
Bottlenose Dolphin ◽  
Tursiops Truncatus ◽  
Site Fidelity ◽  
Bottlenose Dolphins ◽  
Social Groups ◽  
Foraging Strategies ◽  
Association Patterns ◽  
Simple Ratio ◽  
Water Depths

Little is known about the behavior of offshore dolphin populations. Our purpose was to distinguish and describe stable social groups of bottlenose dolphins (Tursiops truncatus) between inshore and offshore West End, Grand Bahama Island (26°42'N, 79°00'W). Photoidentification was conducted from May to September, 1994 to 1996. A simple ratio index described association patterns between dolphins. Multidimensional scaling of association indices (n = 1711 dolphin pairs) distinguished two dolphin communities consisting of 28 dolphins (19 of known sex) found inshore and 15 dolphins (12 of known sex) found greater than or equal to 27 km offshore. Eight of the 15 offshore dolphins were opportunistically photographed in the same region between 1986 and 1990. The two communities were found at different water depths (Mann-Whitney U test, p < 0.01), over distinct bottom types (Kruskal-Wallis test, p < 0.01), and used different bottom-foraging strategies. Long-term site fidelity of up to 10 years and repeated dolphin associations of up to 8 years occurred greater than or equal to 27 km from shore. Dolphins sighted greater than or equal to 15 times averaged 48 associates (SD = 11, n = 28). A dolphin's closest associate was of the same gender 74% of the time. This study is the first to report long-term site fidelity and association patterns of bottlenose dolphins found far from shore.

Use of photo-identification data to quantify mother–calf association patterns in bottlenose dolphins

2003 ◽  
Vol 81 (8) ◽  
pp. 1421-1427 ◽  
Author(s):  
Kate Grellier ◽  
Philip S Hammond ◽  
Ben Wilson ◽  
Carol A Sanders-Reed ◽  
Paul M Thompson
Keyword(s):  
Bottlenose Dolphin ◽  
Tursiops Truncatus ◽  
Bottlenose Dolphins ◽  
Small Population ◽  
Association Patterns ◽  
Photo Identification ◽  
Dolphin Population ◽  
The Mean ◽  
First Time

For social mammals living in fission–fusion societies, the mother–infant bond is long and extends beyond the nursing period. We successfully developed a technique, using photo-identification data, to quantify mother–calf association patterns in a small population of bottlenose dolphins, Tursiops truncatus, off eastern Scotland. By statistically comparing association indices between young calves and their associates we assigned 17 individual adults as mothers to 20 young calves with a 5% level of probability. The mean index of association between calves and mothers remained high until at least year 8 of life. While calves were still found in the same schools as their mother, they surfaced beside her less often as their age increased. This is the first time that the mother–calf bond has been quantitatively assessed for any bottlenose dolphin population inhabiting temperate waters. Results are compared with those from subtropical populations and are discussed with respect to the viability of this population.

Age distribution of breeding female Antarctic fur seals in relation to changes in population growth rate

1990 ◽  
Vol 68 (10) ◽  
pp. 2209-2213 ◽  
Author(s):  
I. L. Boyd ◽  
N. J. Lunn ◽  
P. Rothery ◽  
J. P. Croxall
Keyword(s):  
Population Growth ◽  
Survival Rates ◽  
Age Distribution ◽  
Adult Survival ◽  
South Georgia ◽  
Breeding Female ◽  
Fur Seals ◽  
Rate Of Increase ◽  
The Mean ◽  
Antarctic Fur Seals

The age distribution of breeding female Antarctic fur seals at Bird Island, South Georgia, in 1988 was compared with the age distribution of a sample obtained in 1971–1973. The mean age in 1971–1973 was 7.41 (SE = 0.26) years and in 1988 it was 6.93 (SE = 0.20) years. After correction for age-dependent arrival time at the pupping beach in 1988, the mean age was 6.22 (SE = 0.14 years), which was significantly lower than in 1971–1973. Indicators of population size suggested that population growth at Bird Island had declined to below 3% annually by 1988 compared with rapid growth (17%) in 1958–1972. Exponential models fitted to the frequency distribution of age-classes greater than age 5 years and corrected for the rate of increase of the population gave adult survival rates of 0.66 (SE = 0.03) and 0.88 (SE = 0.02) for the 1988 and 1971–1973 samples, respectively. The reduced apparent adult survival rate in the 1988 sample was probably caused by emigration brought about by high densities of females on the pupping beaches. There are few signs from this analysis that the fur seal population at South Georgia is close to carrying capacity.

Size-Biased Survival in Steelhead Trout (Oncorhynchus mykiss): Back-Calculated Lengths from Adults' Scales Compared to Migrating Smolts at the Keogh River, British Columbia

1989 ◽  
Vol 46 (11) ◽  
pp. 1853-1858 ◽  
Author(s):  
B. R. Ward ◽  
P. A. Slaney ◽  
A. R. Facchin ◽  
R. W. Land
Keyword(s):  
Salt Water ◽  
Survival Rates ◽  
Length Distribution ◽  
Adult Survival ◽  
Steelhead Trout ◽  
Island Size ◽  
Back Calculation ◽  
Males And Females ◽  
The Mean ◽  
Calculation Procedures

Lengths of wild, winter-run steelhead smolts, estimated by back-calculation procedures from adults' scales, were compared with observed lengths of migrating smolts sampled near the mouth of the Keogh River, Vancouver Island. Size-biased smolt-to-adult survival rates were estimated for several length categories by utilizing length frequencies from observed smolts, smolt length frequencies which were back calculated from adults' scales, smolt yield, and adult returns. Back-calculated smolt length (BSL) of adults returning from smolts of 1977 to 1982 averaged 193 mm compared to 176 mm for observed smolt length (OSL). Mean BSL was larger than OSL in every year. Adults from odd-numbered smolt years had larger BSL than adults from even-numbered smolt years similar to the pattern in OSL. BSL increased with increased years spent in salt water, based on ageing adults' scales. Males and females had different BSL based on number of years spent in fresh water and salt water, although they exhibited the same mean BSL overall. The smolt-to-adult survival estimates were in close agreement with previous estimates derived from the mean OSL. Predictability of survival in the ocean based on the length of smolts was extended over a broad range of the length distribution of wild steelhead smolts.

scholarly journals Development, biology, and life table parameters of the predatory species, Clitostethus brachylobus Peng, Ren & Pang 1998 (Coleoptera: Coccinellidae), when fed on the whitefly, Bemisia tabaci (Genn.)

2020 ◽  
Vol 30 (1) ◽  
Author(s):  
Xingmin Wang ◽  
Hui Deng ◽  
Cailian Du ◽  
Shaukat Ali
Keyword(s):  
Bemisia Tabaci ◽  
Survival Rates ◽  
Adult Emergence ◽  
Reproductive Rate ◽  
Adult Survival ◽  
Life Stages ◽  
Life Table Parameters ◽  
Net Reproductive Rate ◽  
Female Longevity ◽  
The Mean

Abstract The predatory species, Clitostethus brachylobus Peng, Ren & Pang 1998 (Coleoptera: Coccinellidae), native to China, has been reported as a predator of the whitefly species, Bemisia tabaci (Genn.). Present study describes the development and biological characteristics of C. brachylobus. Developmental periods of different immature stages showed significant differences, when fed on different life stages of B. tabaci. Prey consumption capacity was reduced by the increase in prey age. Female longevity was 193.5 days, whereas fecundity was 154.70 eggs/female. Net reproductive rate was 53.60, whereas the mean generation time was 102.64 days. The daily adult survival rates gradually decreased 120 h post-adult emergence.

Comparative review of Pacific salmon survival rates

1995 ◽  
Vol 52 (6) ◽  
pp. 1327-1338 ◽  
Author(s):  
Michael J. Bradford
Keyword(s):  
Life History ◽  
Survival Data ◽  
Coho Salmon ◽  
Pacific Salmon ◽  
Survival Rates ◽  
Adult Survival ◽  
Life History Stages ◽  
Comparative Review ◽  
History Of ◽  
The Mean

I collated estimates of survival from the literature for naturally reproducing populations of the five major commercially harvested species of Pacific salmon (Oncorhynchus spp.) and compared the mean and variability of survival across species and life-history stages. The conclusion that survival rates can be described with a lognormal distribution was extended to include both the marine and freshwater stages. Average egg–fry survival of pink (O. gorbuscha), chum (O. keta), and sockeye (O. nerka) salmon was similar (average 7%) but was significantly lower than that of coho salmon (O. kisutch, 19%). The egg–smolt survival of chinook (O. tshawytscha) was much higher than coho or sockeye that also rear in freshwater for similar periods (7 compared with 1–2%). No direct estimates exist for the marine survival rate of naturally spawning chinook stocks; however, from fecundity and freshwater survival data a species average of 1–2% was derived. Across all species freshwater contributes slightly more to total variation in egg–adult survival than does the ocean, and the schedule of mortality during the egg–adult interval depends on the natural history of each species.

scholarly journals Female reproductive output in a Mediterranean bottlenose dolphin Tursiops truncatus population

2020 ◽  
Vol 29 ◽  
pp. 123-136
Author(s):  
MF Blasi ◽  
C Bruno ◽  
L Boitani
Keyword(s):  
Bottlenose Dolphin ◽  
Tursiops Truncatus ◽  
Reproductive Output ◽  
Bottlenose Dolphins ◽  
Reproductive Pattern ◽  
Photo Identification ◽  
Conservation Actions ◽  
Dolphin Population ◽  
The Mean ◽  
June July

The reproductive output of wild bottlenose dolphins Tursiops truncatus has extensively been investigated; nevertheless, it remains widely unexplored in the Mediterranean Sea. We investigated the reproductive history of female bottlenose dolphins in the Aeolian Archipelago (Italy). Thirteen years of photo-identification data were used to track the reproductive pattern of 7 females and their 16 calves. The birth period was accurately estimated within 1 mo for 6 calves (37.5%), peaking in June/July. The mean number of calves for females was 2.3 ± 1.1 (SD), ranging from 1 to 4. The mean interbirth interval was 3.5 ± 1.6 yr, ranging from 2 to 7 yr. The mean weaning age was 3.2 ± 0.6 yr, although 1 calf may have been weaned as late as its fifth birthday. Mother-calf postweaning associations were tracked for 9 calves and ranged from 4 to 10 yr of residence in the maternal group of the calf. The age of first pregnancy was 7.5 yr. The number of calves was influenced by the mean maternal group size, with females that were sighted in larger groups having more calves. However, the number of calves was not influenced by the strength of the associations of mothers with other females. Calf mortality by age 1 was high (12.5%). Two juveniles also died postweaning within 6 yr of their birth. Finally, 2 females may have died during the study, as they were not re-sighted at the end of the study. Our results highlight the need to implement urgent conservation actions to protect this bottlenose dolphin population.

Persistence of giants: population dynamics of the limpet Scutellastra laticostata on rocky shores in Western Australia

2020 ◽  
Vol 646 ◽  
pp. 79-92
Author(s):  
RE Scheibling ◽  
R Black
Keyword(s):  
Population Dynamics ◽  
Western Australia ◽  
Size Structure ◽  
Survival Rates ◽  
Maximum Size ◽  
High Rate ◽  
Adult Survival ◽  
Rocky Shores ◽  
Adult Size ◽  
Decadal Time Scale

Population dynamics and life history traits of the ‘giant’ limpet Scutellastra laticostata on intertidal limestone platforms at Rottnest Island, Western Australia, were recorded by interannual (January/February) monitoring of limpet density and size structure, and relocation of marked individuals, at 3 locations over periods of 13-16 yr between 1993 and 2020. Limpet densities ranged from 4 to 9 ind. m-2 on wave-swept seaward margins of platforms at 2 locations and on a rocky notch at the landward margin of the platform at a third. Juvenile recruits (25-55 mm shell length) were present each year, usually at low densities (<1 m-2), but localized pulses of recruitment occurred in some years. Annual survival rates of marked limpets varied among sites and cohorts, ranging from 0.42 yr-1 at the notch to 0.79 and 0.87 yr-1 on the platforms. A mass mortality of limpets on the platforms occurred in 2003, likely mediated by thermal stress during daytime low tides, coincident with high air temperatures and calm seas. Juveniles grew rapidly to adult size within 2 yr. Asymptotic size (L∞, von Bertalanffy growth model) ranged from 89 to 97 mm, and maximum size from 100 to 113 mm, on platforms. Growth rate and maximum size were lower on the notch. Our empirical observations and simulation models suggest that these populations are relatively stable on a decadal time scale. The frequency and magnitude of recruitment pulses and high rate of adult survival provide considerable inertia, enabling persistence of these populations in the face of sporadic climatic extremes.

Seasonal Abundance and Site Fidelity of Bottlenose Dolphins (Tursiops truncatus) in Mississippi Sound

2004 ◽  
Vol 30 (2) ◽  
pp. 299-310 ◽  
Author(s):  
Carrie W. Hubard ◽  
Kathy Maze-Foley ◽  
Keith D. Mullin ◽  
William W. Schroeder
Keyword(s):  
Tursiops Truncatus ◽  
Site Fidelity ◽  
Bottlenose Dolphins ◽  
Seasonal Abundance ◽  
Mississippi Sound
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