Evaluation of a Neck Mounted 2‐Hourly Activity Meter System for Detecting Cows About to Ovulate in Two Paddock‐Based Australian Dairy Herds

Two studies were conducted to assess the performance of a commercially available neck‐mounted activity meter to detect cows about to ovulate in two paddock‐based Holstein‐Friesian dairy herds. The activity monitoring system recorded cow activity count in 2‐hourly periods. Study I investigated the ability of the system to detect cow ovulatory periods in dairy herds managed in two different Australian environments and breeding systems using five activity alert algorithms. Herd 1 consisted of approximately 130 milking cows calving year‐round in a sub‐tropical environment and kept in a single dry lot paddock. Herd 2 consisted of approximately 400 milking cows calving seasonally in a temperate climate and fed pasture by rotation through multiple grazing paddocks. Ovulatory periods and non‐ovulatory days were identified using milk progesterone monitoring alone or in combination with ovarian ultrasonography; using these ‘gold standards’ 141 and 135 ovulatory periods were identified in 64 and 135 cows in Herds 1 and 2 respectively. Sensitivity of the activity monitoring system for detecting cow ovulatory periods ranged from 79.4% to 94.1%, specificity from 90.0% to 98.2% and positive predictive value from 35.8% to 75.8%. Study II investigated the ability of the activity meter system to predict the timing of ovulations in paddock‐based pasture‐fed dairy cattle (Herd 2). The time of ovulation was estimated by repeat trans‐rectal ovarian ultrasonography at approximately 0, 12, 24 and 36 h after artificial insemination (AI). The mean times (±SD) from onset and end of increased activity to ovulation were 33.4 ± 12.4 and 17.3 ± 12.8 h respectively (n = 94). Fifty per cent of cows (n = 47) ovulated within the 8‐h period between 30 to 38 hs after the onset of increased activity, 76.6% (n = 72) within the 16 h between 24 to 40 h, 85.1% (n = 80) within the 24 h between 18 and 42 h and 90.4% (n = 85) within the 32 h from 19 to 51 h after the onset of increased activity. Results from these studies show that in paddock‐based dairy cows in two diverse management systems, this neck‐mounted activity meter system detects high proportions of cows that are about to ovulate and provides a useful indication of when ovulation is likely to occur. However, the specificities and positive predictive values using the algorithms assessed may be lower than desirable.     

Acclimation to a low oxygen environment alters the hematology of largemouth bass (Micropterus salmoides)

One of the most severe impacts of urbanization on aquatic systems is the increasing presence of low oxygen environments caused by anthropogenic sources of pollution. As urbanization increases nationally and globally, it is becoming exceedingly important to understand how hypoxia affects aquatic fauna, especially fish species. In an effort to better understand the impacts of prolonged hypoxia on fishes, largemouth bass were held at 3.0 and 9.0 mg L^?1 for 50 days, which has previously shown to be temporally sufficient to impart plastic phenotypic changes. Following the holding period, fish from each group were subjected to a low dissolved oxygen (DO) challenge of 2.0 mg L^?1 for 6 h, and their physiological and hematological parameters were compared with control fish held for 6 h with no change in DO. There were no differences in the physiological stress responses between the two holding groups; however, the low oxygen holding group had increased hemoglobin and hematocrit levels following the 6-h low oxygen challenge compared with the high oxygen group. These results suggest largemouth bass exposed to chronic low oxygen conditions, either naturally or anthropogenically, may possess a beneficial advantage of increased oxygen uptake capacity during periods of low oxygen.     

The physiological consequences of catch‐and‐release angling: perspectives on experimental design,interpretation, extrapolation and relevance to stakeholders

Over the past 20 years, there has been a dramatic increase in the use of physiological tools and experimental approaches for the study of the biological consequences of catch‐and‐release angling practices for fishes. Beyond simply documenting problems, physiological data are also being used to test and refine different strategies for handling fish such that stress is minimised and survival probability maximised, and in some cases, even for assessing and facilitating recovery post‐release. The inherent sensitivity of physiological processes means that nearly every study conducted has found some level of – unavoidable – physiological disturbance arising from recreational capture and subsequent release. An underlying tenet of catch‐and‐release studies that incorporate physiological tools is that a link exists between physiological status and fitness. In reality, finding such relationships has been elusive, with further extensions of individual‐level impacts to fish populations even more dubious. A focus of this article is to describe some of the challenges related to experimental design and interpretation that arise when using physiological tools for the study of the biological consequences of catch‐and‐release angling. Means of overcoming these challenges and the extrapolation of physiological data from individuals to the population level are discussed. The argument is presented that even if it is difficult to demonstrate strong links to mortality or other fitness measures, let alone population‐level impacts of catch‐and‐release, there remains merit in using physiological tools as objective indicators of fish welfare, which is an increasing concern in recreational fisheries. The overarching objective of this paper is to provide a balanced critique of the use of physiological approaches in catch‐and‐release science and of their role in providing meaningful information for anglers and managers.     

The influence of hook size, type, and location on hook retention and survival of angled bonefish (Albula vulpes)

Bonefish (Albula spp.) support a circum-tropical sport fishery in which anglers predominantly release angled fish. The influence of hook location, size, and type on hook retention, post-release feeding ability and survival were evaluated. Overall, 46% of bonefish held in large holding tanks expelled hooks within a 14-day observation period. Hooks located in the lip were expelled 2.6 times more frequently than hooks located in the gut. Barbless hooks were expelled 3.9 times faster when located deep in the oral cavity compared to barbed hooks, but there was no difference in expulsion rates among barbed and barbless hooks in shallow-hooked fish. For the two hook sizes studied, hook size had no impact on hook expulsion rates or duration of hook retention regardless of hook location or type. The presence of a hook had no significant effect on weight change, indicating the presence of a hook did not impede feeding ability. No post-release mortality was observed for bonefish during the short duration of this study. Leaving a difficult to remove hook in a bonefish is recommended to increase the likelihood of post-release survival, especially in cases where the threat of bonefish predators is high.     

Physiological effects of ice‐angling capture and handling on northern pike,Esox lucius

Understanding how released fish recover following capture is vital information for researchers examining the effects of angling on exploited populations. This information is virtually non‐existent for fish angled through the ice in winter, despite the popularity of ice‐angling in many northern areas. To address this gap, 60 northern pike, Esox lucius L., were angled through the ice from an impoundment in eastern Wisconsin, USA, and subjected to one of ten combinations of handling and recovery duration. Plasma samples were collected and analysed for cortisol, lactate and glucose. The results showed a delayed response in the elevation of plasma variables, and a significant interaction between air exposure and recovery time for plasma lactate. No fish suffered mortality during the period of holding. Collectively, these data suggest that northern pike are physiologically resilient to ice‐angling capture stress as long as air exposure times are kept at 4 min or less.     

Strategies for the capture and transport of bonefish, Albula vulpes, from tidal creeks to a marine research laboratory for long-term holding

Throughout their circumtropical distribution, bonefish ( Albula spp.) play a vital role in local economies as a highly prized sport fish. Recent interest in stock enhancement to sustain bonefish fisheries has led to the recognition that there currently are no data on how to live capture large numbers of adults (potential broodstock), transport them to captive facilities and how to handle them to ensure high survival. The objective of this study was to develop strategies for the capture and relocation of wild bonefish to a marine research holding facility to enable basic research and explore the potential for culturing bonefish for stock enhancement. Bonefish Albula vulpes (Linnaeus, 1758) were captured as they entered or left tidal creeks on Eleuthera, The Bahamas using seine nets and then transported by boat or truck to the laboratory. The relocation process evoked secondary stress responses at the metabolic, osmoregulatory and haematological levels as indicated by changes in blood glucose, lactate, haematocrit and ion values, relative to control fish. Physical and behavioural disturbances were also observed in bonefish that were unable to acclimate to laboratory conditions. Successful laboratory acclimation and long-term holding of wild bonefish was achieved through an adaptive learning process, whereby we identified a series of strategies and handling techniques to facilitate the acclimation of wild adult bonefish to captivity. This knowledge will enable future laboratory research on bonefish and is a prerequisite to the culture of this highly prized sport fish, and other sub-tropical and tropical marine species.