Assessment of Reproductive Status in Australian Freshwater Crocodiles (Crocodylus johnstoni) by Ultrasound Imaging

Copeia ◽  
1997 ◽  
Vol 1997 (4) ◽  
pp. 851 ◽  
Author(s):  
Anton D. Tucker ◽  
Colin J. Limpus
Keyword(s):  
Ultrasound Imaging ◽  
Reproductive Status ◽  
Crocodylus Johnstoni ◽  
Australian Freshwater

scholarly journals Ultrasound imaging identifies life history variation in resident Cutthroat Trout

PLoS ONE ◽  
2021 ◽  
Vol 16 (2) ◽  
pp. e0246365
Author(s):  
Kellie J. Carim ◽  
Scott Relyea ◽  
Craig Barfoot ◽  
Lisa A. Eby ◽  
John A. Kronenberger ◽  
...  
Keyword(s):  
Life History ◽  
Ultrasound Imaging ◽  
Life Histories ◽  
Cutthroat Trout ◽  
Error Rates ◽  
Reproductive Status ◽  
Lifetime Reproductive Success ◽  
Life History Variation ◽  
Westslope Cutthroat Trout ◽  
Isolated Populations

Human activities that fragment fish habitat have isolated inland salmonid populations. This isolation is associated with loss of migratory life histories and declines in population density and abundance. Isolated populations exhibiting only resident life histories may be more likely to persist if individuals can increase lifetime reproductive success by maturing at smaller sizes or earlier ages. Therefore, accurate estimates of age and size at maturity across resident salmonid populations would improve estimates of population viability. Commonly used methods for assessing maturity such as dissection, endoscopy and hormone analysis are invasive and may disturb vulnerable populations. Ultrasound imaging is a non-invasive method that has been used to measure reproductive status across fish taxa. However, little research has assessed the accuracy of ultrasound for determining maturation status of small-bodied fish, or reproductive potential early in a species’ reproductive cycle. To address these knowledge gaps, we tested whether ultrasound imaging could be used to identify maturing female Westslope Cutthroat Trout (Oncorhynchus clarkii lewisi). Our methods were accurate at identifying maturing females reared in a hatchery setting up to eight months prior to spawning, with error rates ≤ 4.0%; accuracy was greater for larger fish. We also imaged fish in a field setting to examine variation in the size of maturing females among six wild, resident populations of Westslope Cutthroat Trout in western Montana. The median size of maturing females varied significantly across populations. We observed oocyte development in females as small as 109 mm, which is smaller than previously documented for this species. Methods tested in this study will allow researchers and managers to collect information on reproductive status of small-bodied salmonids without disrupting fish during the breeding season. This information can help elucidate life history traits that promote persistence of isolated salmonid populations.

Morphometric analysis of the Australian freshwater crocodile (Crocodylus johnstoni)

2017 ◽  
Vol 65 (2) ◽  
pp. 97 ◽  
Author(s):  
Glenn P. Edwards ◽  
Grahame J. Webb ◽  
S. Charlie Manolis ◽  
Alex Mazanov
Keyword(s):  
Morphometric Analysis ◽  
Body Measurements ◽  
Body Parts ◽  
Allometric Growth ◽  
Relative Growth ◽  
Crocodylus Johnstoni ◽  
Arnhem Land ◽  
Freshwater Crocodile ◽  
Crocodylus Porosus ◽  
Australian Freshwater

We conducted a morphometric analysis of 279 Crocodylus johnstoni, using specimens from the McKinlay River (n = 265) and Arnhem Land (n = 14), to meet the management need for predicting body size of C. johnstoni from isolated body parts. The results also allow reconstruction of C. johnstoni dimensions for comparison with other crocodilian species. We detected sexual dimorphism in some body measurements from the McKinlay River, and geographic variation in the morphology of McKinlay River and Arnhem Land populations, but differences were slight. There is pronounced allometric growth in C. johnstoni in the immediate post-hatching phase, largely due to elongation of the snout after exiting the confines of the egg. We compared the size, shape and relative growth of C. johnstoni with that of other crocodilian species for which equivalent data are available, but particularly the other Australian crocodile, Crocodylus porosus. C. porosus has a proportionately longer tail and a shorter but wider snout than C. johnstoni, and we discuss possible ecological correlates of these and other differences.

Movements and Home Ranges of Crocodylus johnstoni in the Lynd River, Queensland

1997 ◽  
Vol 24 (4) ◽  
pp. 379 ◽  
Author(s):  
A. D. Tucker ◽  
C. J. Limpus ◽  
H. I. McCallum ◽  
K. R. McDonald
Keyword(s):  
Field Trips ◽  
Home Ranges ◽  
Adult Males ◽  
Dominance Hierarchies ◽  
Breeding Sites ◽  
Crocodylus Johnstoni ◽  
Upstream Direction ◽  
A Minor ◽  
Australian Freshwater ◽  
Local Dominance

Movements of Australian freshwater crocodiles, Crocodylus johnstoni, were examined by a mark–recapture study spanning 20 years in the Lynd River, Queensland. After adjustment for detection bias, there was a minor upstream direction to movements. Seasonal changes of location were not evident from field trips taken only twice yearly. Annual movements averaged less than 1 km except for those of pubescent males, which appeared to be nomadic. Creche dispersal was randomly directed but associated with a threshold in mass/length ratio. On average, males were found further from previous capture sites than were females. Adults of both sexes moved shorter distances than did immature crocodiles with a clear reduction in movements occurring as mass/length ratios approached 0·17 kg per cm snout–vent length. Reduced movement at that general size ratio probably indicated the onset of territoriality associated with maturity. Females usually remained near breeding sites even in years when they did not breed. Nomadic tendencies of pubescent males are probably associated with unsuccessful attempts at entering local dominance hierarchies. Linear home ranges were estimated to be 1·5–1·9 km for immature animals, 1·2 km for pubescent females, 30·3 km for pubescent males, 0·6 km for mature females and 1·6 km for adult males.

Remote monitoring of crocodilians: implantation, attachment and release methods for transmitters and data-loggers

2009 ◽  
Vol 60 (4) ◽  
pp. 284 ◽  
Author(s):  
Craig E. Franklin ◽  
Mark A. Read ◽  
Peter G. Kraft ◽  
Niko Liebsch ◽  
Steve R. Irwin ◽  
...  
Keyword(s):  
Physiological Variables ◽  
Crocodylus Johnstoni ◽  
Data Loggers ◽  
Archival Tags ◽  
Crocodylus Porosus ◽  
Electronic Tags ◽  
Free Ranging ◽  
Australian Freshwater ◽  
Term Management

Crocodilians are by their very nature difficult animals to study. However, research on wild animals is essential for the development of reliable long-term management. Here, we describe methods for the acquisition and monitoring of behavioural and physiological variables from free-ranging crocodilians through the use of archival tags (data-loggers) and via satellite, radio and acoustic telemetry. Specifically, the attachment or implantation of electronic tags is described and examples provided of the type of data that can be collected. Our research group has used a combination of approaches to monitor the movements, diving activity, body temperatures and heart rates of crocodilians, including studies on the Australian freshwater crocodile (Crocodylus johnstoni), the estuarine crocodile (Crocodylus porosus) and the caiman (Caiman latirostris). Each approach or method presents unique challenges and problems, chiefly as a consequence of differences in body morphology and size of the crocodilian species, their behaviours and the habitats they occupy.

Proctocaecum blairi sp. nov. (Digenea, Cryptogonimidae) from the freshwater crocodile, Crocodylus johnstoni, in Northern Territory, Australia

2010 ◽  
Vol 55 (3) ◽  
Author(s):  
Vasyl Tkach ◽  
Scott Snyder
Keyword(s):  
New Species ◽  
Relative Length ◽  
Anterior Testis ◽  
Northern Territory ◽  
The Body ◽  
Body Proportions ◽  
Diagnostic Features ◽  
Crocodylus Johnstoni ◽  
Freshwater Crocodile ◽  
Australian Freshwater

AbstractProctocaecum blairi sp. nov. is described from specimens found in the intestine of an Australian freshwater crocodile, Crocodylus johnstoni, from Northern Territory, Australia. The most important diagnostic features of the new species are the body proportions and size, the position of the pharynx (relative length of the prepharynx and oesophagus), the relative length and position of the vitelline fields, and the number, shape and size of the circumoral spines. The new species is morphologically most similar to Proctocaecum atae, P. elongatum, P. crocodili, P. gairhei and Acanthostomum slusarskii. It differs from all of these species in having a much longer prepharynx, and differs from both P. atae and P. crocodili in having a much longer body and posteriorly situated vitelline fields. Proctocaecum blairi sp. nov. differs from P. elongatum in having a shorter body, a greater forebody to hindbody ratio, a much smaller ventral sucker, and a higher number of circumoral spines (23 vs 21 in P. elongatum). The new species differs from P. gairhei in possessing a much larger body length:width ratio and an ovary separated from the anterior testis by a seminal receptacle. Acanthostomum slusarskii lacks a gonotyl and has fewer circumoral spines than the new species. Proctocaecum blairi sp. nov. is the third species of Proctocaecum and the fourth cryptogonimid species known from crocodiles in Australia.

Validation of skeletochronology to determine age of freshwater crocodiles (Crocodylus johnstoni)

1997 ◽  
Vol 48 (4) ◽  
pp. 343 ◽  
Author(s):  
Anton D. Tucker
Keyword(s):  
Age Estimation ◽  
Egg Laying ◽  
Interference Microscopy ◽  
Adult Males ◽  
Size Estimation ◽  
Thin Sections ◽  
Crocodylus Johnstoni ◽  
Old Adult ◽  
Different Seasons ◽  
Australian Freshwater

Age was estimated for wild Australian freshwater crocodiles from skeletochronology of growth marks in postoccipital osteoderms. Growth marks were distinct and counted reliably in unstained calcified thin sections (60–80 µm) viewed by Nomarski interference microscopy. The periodicity of growth marks was validated directly from crocodiles of known age (up to 19 years) and from individuals sampled sequentially in different seasons. Growth marks comprised annuli deposited in winter and zones deposited in summer. Errors in age estimation for small crocodiles resulted from difficulty in assigning the growing edge as either a zone or an annulus. No osseous remodelling was noted for immature animals. Age estimates for adult females became unreliable as previous annuli were obscured by osseous remodelling, presumably resulting from calcium mobilization by egg-laying females. Old adult males continued to deposit annuli, but these were more difficult to distinguish, being more closely spaced than in young crocodiles. Skeletochronology permitted reliable (coefficient of variation, 3·4%) and accurate (±1 year) age estimation up to about 20 years. Osteoderm dimensions were strongly correlated with average snout–vent length, mass and age and have acceptable potential as an indirect means of age and size estimation for Crocodylus johnstoni.

scholarly journals A Comparison of Nonlethal Methods for Evaluating the Reproductive Status of Female Coastal Cutthroat Trout

2014 ◽  
Vol 5 (1) ◽  
pp. 183-190 ◽  
Author(s):  
Peter D. Bangs ◽  
James J. Nagler
Keyword(s):  
Ultrasound Imaging ◽  
Lipid Content ◽  
Cutthroat Trout ◽  
Reproductive Status ◽  
Annual Reproductive Cycle ◽  
Body Lipid ◽  
Oncorhynchus Clarkii ◽  
The Pacific ◽  
Coastal Cutthroat Trout ◽  
Estradiol Levels

Abstract Knowledge of the state of sexual development is important for management of coastal cutthroat trout Oncorhynchus clarkii clarkii, a fish species targeted for sport fishing throughout its range along the Pacific coast of North America. The purpose of this study was to compare the nonlethal methods of ultrasound imaging, body lipid content, and the measurement of plasma vitellogenin and estradiol levels for assessing the reproductive status of female coastal cutthroat trout. This was examined in a population living in Florence Lake, Alaska, during the spring–early autumn period of the annual reproductive cycle. All methods, except body lipid content, were effective at determining maturity status in either the spring (ultrasound imaging), or spring and autumn (plasma vitellogenin and estradiol). These approaches could be useful for conducting nonlethal assessments of length- or age-at-maturity on populations of coastal cutthroat trout that are small, have conservation concerns, or are heavily utilized by anglers.

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