Topic
Morus serrator
About: Morus serrator is a research topic. Over the lifetime, 47 publications have been published within this topic receiving 589 citations.
Papers
TL;DR: There is considerable spatial and temporal overlap in the harvesting of pilchards by both gannets and the commercial pilchard fishery, but, limited information on the abun- dance or availability of prey stocks inhibits quantification of this level of competition.
Abstract: Prey consumption of Australasian gannets (Morus serrator) breeding in Port Phillip Bay, Victoria, was investigated between 1997 and 2000 and the potential overlap between gannets and commercial fisheries in this region was assessed. Approximately 1000 gannets now breed in Port Phillip Bay annually and typically feed on inshore pelagic schooling fish species, such as pilchards (Sardinops sagax), barracouta (Thyrsites atun) and, to a lesser extent, anchovy (Engraulis australis), garfish (Hyporhamphus melanochir), mackerel (Scomber australasicus) and other species. Nutritional analyses of the major prey items in the gannet diet suggests that gannets may target prey species of higher energy density; however, variations in their representation in the gannet diet between breeding periods probably reflect changes in local availability. The daily energy requirement of individual gannets breeding in Port Phillip Bay, determined from activity patterns and activity-specific metabolic rates, was calculated as 4561 kJ d 1 . Using a bioenergetics model it was estimated that gannets breeding in Port Phillip Bay consume in total some 228.2 tonnes of prey during the breeding period, including 37.8 t of pilchard, 80.5 t of barracouta, 26.5 t of anchovy and 27.5 t of garfish. The potential foraging ranges of gannets during the breeding period were estimated at approximately 100 km. Within this zone all of the major prey items in the gannet diet are taken to some extent commercially, although only pilchards are specifically targeted as a fishery in large quantities. There is considerable spatial and temporal overlap in the harvesting of pilchards by both gannets and the commercial pilchard fishery, but, limited information on the abun- dance or availability of prey stocks inhibits quantification of this level of competition. Nevertheless, it is likely that the fisheries has the potential to negatively affect gannets. 2001 International Council for the Exploration of the Sea
65 citations
TL;DR: A significant trend towards more frequent, and stronger, El Niño Southern Oscillation events, warmer summer sea surface temperatures in Bass Strait, increased annual catches and catch per unit effort in the Victorian pilchard fishery and potential increased discarding of fisheries bycatch may account for at least some of the observed increase in the Australasian gannet population.
Abstract: The Australasian gannet (Morus serrator) population has increased considerably over the past century, both in New Zealand and Australia. Since 1980, the population in Australian waters has increased threefold, from 6,600 breeding pairs to approximately 20,000 pairs in 1999-2000, a rate of 6% per year. Reasons for the increase in the Australasian gannet population are poorly understood; here we consider the possible effects of recent fluctuations in climatic and oceanographic conditions, and changes in major local commercial fisheries. A significant trend towards more frequent, and stronger, El Nino Southern Oscillation events, warmer summer sea surface temperatures in Bass Strait, increased annual catches and catch per unit effort in the Victorian pilchard (Sardinops sagax) fishery and potential increased discarding of fisheries bycatch may account for at least some of the observed increase in the Australasian gannet population. The potential interactive effects of these factors on prey distribution and abundance and consequently on gannet numbers are discussed.
64 citations
TL;DR: Assumptions that both membership in social pairs and different copulatory positions can serve as reliable behavioural proxies for field-based sex identification in this colonial and obligately biparental seabird are validated.
Abstract: The availability of molecular methods for avian sex identification has revolutionised the study of sexual differences in behaviour, morphology, life-history traits and conservation management. We implemented the recommendations of a recent review of DNA-based sex-identification by (1) verifying the sex-specificity and (2) estimating the accuracy of different sex-assignment methods in an apparently monomorphic seabird, the Australasian gannet (Morus serrator). The polymerase chain reaction (PCR) method based on the amplification of the sex-linked chromodomain-helicase-DNA binding gene (CHD) repeatedly assigned the same sex in 96% (n = 27 replicates) and correctly sexed all individuals with known gonadal anatomy (n = 6). PCR and sex-specific restriction fragment length polymorphism (RFLPs) showed agreement for 99.5% of individuals (n = 201). DNA-sexed pairs known to be social mates consisted of a male and a female in 96% of pairs sexed by PCR (n = 77) and 98% of pairs sexed by RFLP (n = 65). DNA-sexed females were in the bottom and males in the top copulatory position in 86% of observed copulations (n = 43 individuals). These results validate assumptions that both membership in social pairs and different copulatory positions can serve as reliable behavioural proxies for field-based sex identification in this colonial and obligately biparental seabird.
32 citations
TL;DR: Predictors are generated to identify whether differences in Australasian gannet vocalizations play perceptual and functional roles in the breeding and social biology of this long-lived biparental seabird species.
Abstract: The study of the evolution of sexual differences in behavioral and morphological displays requires analyses of the extent of sexual dimorphism across various sensory modalities. In the seabird family Sulidae, boobies show dramatic sexual dimorphism in their vocalizations, and gannet calls have also been suggested to be dimorphic to human observers. This study aimed to evaluate the presence of sexually dimorphic calls in the Australasian gannet (Morus serrator) through the first comprehensive description of its vocalizations recorded at two localities; Cape Kidnappers, where individuals were banded and sexed from DNA samples, and at the Muriwai gannetry, both on the North Island of New Zealand. Calls were first inspected using basic bioacoustic features to establish a library of call element types for general reference. Extensive multivariate tests, based on a dynamic time warping algorithm, subsequently revealed that no sexual differences could be detected in Australasian gannet calls. The analyses, however, indicated extensive and consistent vocal variation between individuals, particularly so in female gannets, which may serve to signal individual identity to conspecifics. This study generates predictions to identify whether differences in Australasian gannet vocalizations play perceptual and functional roles in the breeding and social biology of this long-lived biparental seabird species.
29 citations
TL;DR: The authors of as discussed by the authors found that older adults formed more central nests, laid earlier, and replaced more lost eggs than younger birds, and chicks of older adults were produced earlier and were heavier at comparable ages than those of younger birds.
Abstract: Reproductive parameters of Australasian GannetsMorus serrator breeding at Pope’s Eye in Port Phillip Bay, Victoria, Australia were examined in the 1994—95 breeding period. Contents of individual nests were determined during routine visits, and eggs and chicks measured. Nests and breeding birds were assigned to groups based on position and adults of known age (previously banded as chicks) as indicators. A severe storm in November 1994 removed most nests and resulted in extensive re-laying, particularly by older (centrally nesting) birds. The ability to relay and successfully raise young suggested that food (preferentially Pilchards Sardinops sagax, although gannets take a wide range of fish at this location) was not limiting, being abundant even towards later stages of the breeding cycle. ‘Older’ adults formed more central nests, laid earlier, and replaced more lost eggs than younger birds. Chicks of older adults were produced earlier and were heavier at comparable ages than those of younger birds. Age influences some reproductive parameters, and hence lifetime reproductive success, in this species as it does in other seabirds.
24 citations
Related Topics (5)
Performance Metrics
| Year | Papers |
|---|---|
| 2021 | 3 |
| 2020 | 1 |
| 2018 | 3 |
| 2017 | 2 |
| 2015 | 1 |
| 2014 | 2 |