Shark Survey Techniques
Project Leaders: Dr Andy Danylchuk and Ed Brooks
Background
Survey techniques requiring physical capture are used commonly for the study of sharks; however the negative attributes of such capture events are poorly understood and may have wide reaching population level consequences. Given the conservation focus of many shark research programs, it is critical that the potential impacts of capture techniques be objectively evaluated. We propose to examine the lethal and sub-lethal consequences of capture caused by common survey techniques including longline and drumline surveys. In order to accomplish this, the study has been split into two equally important tasks.
Task 1 will examine the degree of physiological disturbance and physical trauma associated with capture, and task 2 will address post-release survivorship and behavioural variation initiated by these disruptions. Task 1 will establish the degree of physiological stress experienced during capture by monitoring blood chemistry parameters which can be compared with a number of variables including capture gear, capture duration, species and season. Physical trauma will be categorized by hook location and depth as well as any external lacerations.
Task 2 will examine the levels of post-release survivorship and degree of behavioural disruption through the use of a high resolution acoustic telemetry array and tags that transmit the activity level, depth and ambient water temperature of the sharks. Mortality will be assumed if there is no tag movement or a zero activity. The degree of behavioural variation will be monitored immediately post release and over time using activity level, movement patterns, and habitat association as indicators of disruption. This project will lay the foundation for conservation-based cost-benefit analyses when making choices related to the best techniques for surveying sharks.
Task 1 will examine the degree of physiological disturbance and physical trauma associated with capture, and task 2 will address post-release survivorship and behavioural variation initiated by these disruptions. Task 1 will establish the degree of physiological stress experienced during capture by monitoring blood chemistry parameters which can be compared with a number of variables including capture gear, capture duration, species and season. Physical trauma will be categorized by hook location and depth as well as any external lacerations.
Task 2 will examine the levels of post-release survivorship and degree of behavioural disruption through the use of a high resolution acoustic telemetry array and tags that transmit the activity level, depth and ambient water temperature of the sharks. Mortality will be assumed if there is no tag movement or a zero activity. The degree of behavioural variation will be monitored immediately post release and over time using activity level, movement patterns, and habitat association as indicators of disruption. This project will lay the foundation for conservation-based cost-benefit analyses when making choices related to the best techniques for surveying sharks.
Aims & objectives
The main goal of this project is to quantify the physiological stress and associated mortality caused by common techniques for surveying sharks. To meet this goal the research has been divided to address the two tasks:
Task 1 - Using blood chemistry we will assess the level of physiological disturbance associated with longline and drumline capture compared to a control group captured by hook and line. Given the longer duration of capture and more restricted swimming capacity associated with longline and drumline surveys, we hypothesize that a greater level of physiological stress will be inflicted on survey caught fish when compared to the control group. Blood chemistry parameters will be compared across capture method, species, and different demographics within a species such as size, maturity and sex. Other variables will include capture duration, hooking location and environmental parameters including water temperature, dissolved oxygen and salinity. Physical trauma will be categorized by hooking location and depth and the degree of external laceration. This task can stand alone as a very important assessment of the acute physiological disturbances associated with the capture of sharks.
Task 2 - Using visual assessments and passive ultrasonic telemetry, we will assess the post-release mortality of sharks captured using the two survey techniques as well as the control. We hypothesize that the high physiological stress associated with longline and drumline surveys will cause an increase in post-release mortality when compared to a control group. Caribbean reef sharks (Carcharhinus perezi) will be used as a model species for the assessment and their post-release survival tracked with passive ultrasonic telemetry. In addition the sub-lethal effects of capture, such as changes in behavior, will be monitored using the same acoustic telemetry array. We propose to monitor variation in activity level, movement patterns, and habitat selection in Caribbean reef sharks post-release.
Task 1 - Using blood chemistry we will assess the level of physiological disturbance associated with longline and drumline capture compared to a control group captured by hook and line. Given the longer duration of capture and more restricted swimming capacity associated with longline and drumline surveys, we hypothesize that a greater level of physiological stress will be inflicted on survey caught fish when compared to the control group. Blood chemistry parameters will be compared across capture method, species, and different demographics within a species such as size, maturity and sex. Other variables will include capture duration, hooking location and environmental parameters including water temperature, dissolved oxygen and salinity. Physical trauma will be categorized by hooking location and depth and the degree of external laceration. This task can stand alone as a very important assessment of the acute physiological disturbances associated with the capture of sharks.
Task 2 - Using visual assessments and passive ultrasonic telemetry, we will assess the post-release mortality of sharks captured using the two survey techniques as well as the control. We hypothesize that the high physiological stress associated with longline and drumline surveys will cause an increase in post-release mortality when compared to a control group. Caribbean reef sharks (Carcharhinus perezi) will be used as a model species for the assessment and their post-release survival tracked with passive ultrasonic telemetry. In addition the sub-lethal effects of capture, such as changes in behavior, will be monitored using the same acoustic telemetry array. We propose to monitor variation in activity level, movement patterns, and habitat selection in Caribbean reef sharks post-release.