Recruitment of a critically endangered sawfish into a riverine nursery depends on natural flow regimes

The freshwater sawfish (Pristis pristis) was recently listed as the most Evolutionarily Distinct and Globally Endangered (EDGE) animal. The Fitzroy River in the remote Kimberley region of north-western Australia represents a significant stronghold for the species, which uses the freshwater reaches of the river as a nursery. There is also mounting pressure to develop the water resources of the region for agriculture that may substantially affect life history dynamics of sawfish in this system. However, the relationship between hydrology and population dynamics of freshwater sawfish was unknown. We used standardized catch data collected over 17 years to determine how wet season volume influences recruitment of freshwater sawfish into their riverine nursery. Negligible recruitment occurred in years with few days of high flood levels (above 98th percentile of cease-to-flow stage height), and relatively high recruitment occurred in years with 14 or more days of high flood levels. This relationship is indicative of a distinct boom-or-bust cycle, whereby freshwater sawfish rely almost entirely on the few years with large wet season floods, and the brief periods of highest water levels within these years, to replenish juvenile populations in the Fitzroy River nursery. This has direct implications for sustainable water resource management for the Fitzroy River basin in order to preserve one of the last known intact nursery habitats for this globally threatened species

The Vehicle, Spring 1996

Vol. 37, No. 2 Table of Contents Poetry AnyoneKeith Owenspage 2 Of Words and WidgetsJ. Dylan McNeillpage 3 HouseplantsPeter W. Katespage 4 IcarusJeff Vande Zandepage 5 UntitledPatrick F. Kellypage 7 CommuteWhitty Whitesellpage 8 During Graduate SchoolJeff Vande Zandepage 9 NeuteredJason S. Loguepage 10 Bitter WritingJ. Dylan McNeillpage 11 Song to Unknown SoldiersM. Olatoye Bayieupage 12 SoftAmy Haynespage 13 Mother\u27s Crossword PuzzlesMatthew J. Nelsonpage 14 Prose Cold ShowerMatt Parkspage 17 Your Title HereKeith Owenspage 20 Biographies Authorspage 27https://thekeep.eiu.edu/vehicle/1067/thumbnail.jp

The consumer scam: an agency-theoretic approach

Despite the extensive body of literature that aims to explain the phenomenon of consumer scams, the structure of information in scam relationships remains relatively understudied. The purpose of this article is to develop an agency-theoretical approach to the study of information in perpetrator-victim interactions. Drawing a distinction between failures of observation and failures of judgement in the pre-contract phase, we introduce a typology and a set of propositions that explain the severity of adverse selection problems in three classes of scam relationships. Our analysis provides a novel, systematic explanation of the structure of information that facilitates scam victimisation, while also enabling critical scrutiny of a core assumption in agency theory regarding contract design. We highlight the role of scam perpetrators as agents who have access to private information and exercise considerable control over the terms and design of scam relationships. Focusing on the consumer scam context, we question a theoretical assumption, largely taken for granted in the agency literature, that contact design is necessarily in the purview of the uninformed principal

Utility of rostra in the identification of Australian sawfishes (Chondrichthyes: Pristidae)

1. Effective management of critically endangered sawfishes can be a difficult task, in part due to interspecies misidentification. Current methods for identifying sawfishes can be impractical as they are based on morphological features that are often unobservable. Further exploration is required to develop a more reliable means of identification.\ud \ud 2. This study explored the utility of sawfish rostra in determining the species, size and sex of sawfishes, as rostra are commonly the only feature of a sawfish observed by fishers or present in public and private collections.\ud \ud 3. A morphometric and meristic database consisting of over 1100 narrow sawfish (Anoxypristis cuspidata), dwarf sawfish (Pristis clavata), largetooth (or freshwater) sawfish (Pristis pristis; formerly Pristis microdon) and green sawfish (Pristis zijsron) rostra from Australian waters, was statistically analysed.\ud \ud 4. Identification of sawfishes was found to be possible through the use of the variables: inter-tooth spacing, standard rostrum width/standard rostrum length, standard rostrum length/total rostrum length, rostrum tip width/standard rostrum length, and/or rostral tooth count range, although the distinguishing variables were species-dependent.\ud \ud 5. The relationship between standard rostrum length and total length was also observed to vary substantially between most species. Models for estimating total length from standard rostrum length are provided.\ud \ud 6. This study has provided a tool that can be used to identify accurately the species and size of sawfishes by their rostra, and therefore can assist in clarifying historical and contemporary sawfish records, nomenclature and distributions. A better understanding of these issues should allow sawfish conservation strategies to become more focused, and thus more effective

First evidence of spawning migration by goldfish (Carassius auratus); implications for control of a globally invasive species

Goldfish (Carassius auratus) was one of the first fishes to be domesticated and has been widely introduced across the globe, but is now considered one of the world's worst invasive aquatic species. Surprisingly, there is a dearth of information on its spatial and temporal movement patterns, which hampers the development of effective control programmes. We examined the movement patterns of an introduced population of C.auratus in a south-western Australian river using passive acoustic telemetry. The study population had a high residency index within the array (i.e. proportion of all days at liberty that, on average, each fish was detected by a receiver) with fish being detected on 64% of days. The individuals were also reasonably mobile, travelling a mean of 0.30 km (linear river kilometres).day(-1) within the array, and one fish moved 231.3km over the 365-day study period (including 5.4km in a 24hr period). Importantly, C.auratus displayed significant seasonal movement patterns including a clear shift in habitats during its breeding period with most mature individuals being detected in an off-channel wetland during that time. The results of this study strongly suggest that C.auratus undertook a spawning migration into a lentic habitat. These results have important implications for developing control programmes for the species, such as targeting connections to off-channel lentic systems during its breeding period

What is the fate of amputee sawfish?

3 page(s

The Vehicle, Spring 1996

Vol. 37, No. 2 Table of Contents Poetry AnyoneKeith Owenspage 2 Of Words and WidgetsJ. Dylan McNeillpage 3 HouseplantsPeter W. Katespage 4 IcarusJeff Vande Zandepage 5 UntitledPatrick F. Kellypage 7 CommuteWhitty Whitesellpage 8 During Graduate SchoolJeff Vande Zandepage 9 NeuteredJason S. Loguepage 10 Bitter WritingJ. Dylan McNeillpage 11 Song to Unknown SoldiersM. Olatoye Bayieupage 12 SoftAmy Haynespage 13 Mother\u27s Crossword PuzzlesMatthew J. Nelsonpage 14 Prose Cold ShowerMatt Parkspage 17 Your Title HereKeith Owenspage 20 Biographies Authorspage 27https://thekeep.eiu.edu/vehicle/1067/thumbnail.jp