Dale M. Webber

Ultrasonic telemetry, tracking and automated monitoring technology for sharks

Sharks were among the first marine animals to carry telemetry systems because of their size and the need to understand their interactions with humans. Modern telemetry systems can gather many kinds of data (limited only by imagination, funding and sensor types), indicating which animals are near telemetry receivers and what they are doing. Receivers now range from simple autonomous detector units for deployment in mid-water in large-scale grids, to sophisticated automated benthic recorders, to triangulating radio-linked buoy systems (RAP), to ship-borne transponders. In addition, archival tags can now gather and store data even while the shark is away, to be downloaded later. Older types had to be recovered, but popup tags release from sharks automatically, surface and transfer data to satellites, while CHAT tags download whenever queried by a nearby transponding acoustic receiver. Sophisticated animal-borne tags dramatically increase the information gathered about sharks and their environment. The examples provided show the parallel progression of shark biology and acoustic biotelemetry illustrating that telemetry systems are tools for gathering data, which can often be honed to facilitate biological experiments. Future visions include sensors that directly measure shark swimming power and cardiac output, compressing the data so that it can be delivered to RAP systems tracking multiple animals with meter resolution in near real time. CHAT tags as small as 22 mm diameter should be able to return similar data from trips of hundreds of kilometers. Continued communication between biologists and engineers is essential to develop these technologies.

Applications and performance of Radio-Acoustic Positioning and Telemetry (RAPT) systems

RAPT was developed to use systems of semi-autonomous buoys with hydrophones and radio transmitters to continuously monitor the positions and performance of multiple objects, animals and/or people tagged with miniature acoustic transmitters under water. Buoys communicate signal arrival times to shore, ship or aircraft based computers which triangulate positions in three dimensions and decode telemetered information such as heart rate, respiration rate, temperature, salinity and light encoded in pulse intervals. It is the only way of tracking with high-resolution (meters) at intermediate ranges (10’s-1000’s of meters) in seawater and the most accurate in freshwater. The technique is powerful and flexible with wide application, but is constrained by tradeoffs between electrical power and signal accuracy under extreme conditions. Technological solutions to some of these constraints are possible, but optimization of information gathering, in many cases, simply requires more experience and can be achieved by software, information sharing and a cadre of trained personnel.

Squid (Loligo forbesi) performance and metabolic rates in nature

Squid are the fastest swimming invertebrates, but the metabolic cost of speed, as assessed in swim‐tunnels, is several‐fold higher than in fish, making squid appear uncompetitive. Because oxygen consumption can be correlated with jet pressure, it is possible to monitor pressure and thus estimate performance and energy costs in nature. Tracking in course and depth gave a 3‐D view of squid (Loligo forbesi) activities and costs for nearly three animal‐weeks; five days of this included telemetry of jet pressures. These 2–5 kg loliginids hovered off‐bottom most of the time, perhaps to avoid predation or damage to delicate skins. Hovering consumes about 50 ml O2 kg‐1 h‐1, twice as much as resting on bottom and half of overall average costs. Jet pressures were not well correlated with horizontal movements or tidal cycles, suggesting squid may “soar”; to reduce the cost of remaining in active current areas, acting as sit‐and‐wait predators. Maximal aerobic jetting was rare and usually associated with vertical cli...

Costs of Locomotion and Vertic Dynamics of Cephalopods and Fish

The worlds oceans are three‐dimensional habitats that support high diversity and biomass. Because the densities of most of the constituents of life are greater than that of seawater, planktonic and pelagic organisms had to evolve a host of mechanisms to occupy the third dimension. Some microscopic organisms survive at the surface by dividing rapidly in vertically well mixed zones, but most organisms, small and large, have antisinking strategies and structures that maintain vertical position and mobility. All of these mechanisms have energetic costs, ranging from the “foregone metabolic benefits” and increased drag of storing high‐energy, low‐density lipids to direct energy consumption for dynamic lift. Defining the niches in the mesopelagic zone, understanding evolution, and applying such ecological concepts as optimal foraging require good estimates of these costs. The extreme cases above are reasonably well quantified in fishes, but the energetic costs of dynamic physiological mechanisms like swim bladders are not; nor are the costs of maintaining vertical position for the chief invertebrate competitors, the cephalopods. This article evaluates a matrix of buoyancy mechanisms in different circumstances, including vacuum systems and ammonium storage, based on new data on the metabolic cost of creating buoyancy in Sepia officinalis.

Oxygen uptake and nitrogen excretion in two cephalopods, octopus and squid

Abstract 1. 1. During exercise of the squid Illex illecebrosus swimming up to 3 body lengths/sec, resting values at 15°C for both oxygen uptake (11.3 mM O2/kg per hr) and ammonium excretion (1.4 mM NH4/kg per hr) increased about five-fold; both parameters were always correlated with an excretory O:N ratio of 15. 2. 2. In Octopus, both oxygen uptake and ammonium excretion rates at rest were about five-fold lower than in Illex. 3. 3. Urea was 30% of the measured nitrogen excretion in Octopus and 24% in Illex at rest, respectively. 4. 4. During swimming, urea excretion in Illex was irregular and not correlated with ammonium excretion. 5. 5. Glutamic dehydrogenase activity with a significant capability for glutamate oxidation (0.3–3.1 Units/g tissue; 25°C) as well as adenosine deaminase activity (0.4–3.3 units/g tissue) were found in several Illex tissues.

The Use of Acoustic Telemetry in South African Squid Research (2003-2010)

The South African chokka squid, Loligo reynaudii is found along the coast of South Africa, from Southern Namibia in the west to Port Alfred in the east (Augustyn, 1991). Inshore spawning, however, is limited to the South Coast between Plettenberg Bay and Port Alfred (Figure 1) (Augustyn, 1990). As it is these inshore spawning aggregations that are targeted by the squid jigging fishery (Sauer et al., 1992), an in depth knowledge of the spawning process is essential to the development of effective management strategies for this fishery. In addition squid catches are determined to a large extent by the successful formation and size of these aggregations. As a result, the majority of research on the chokka squid has focused on inshore spawning, i.e. environmental effects on spawning (Augustyn, 1990, Roberts, 1998, 2005; Roberts & Sauer, 1994; Roberts & van den Berg, 2002, 2005; Sauer et al. 1991, 1992), the impact of fishing on spawning concentrations (Hanlon et al., 2002; Oosthuizen et al., 2002a; Sauer, 1995; Schön et al. 2002), biological studies (Augustyn 1990; Lipinski & Underhill, 1995; Melo & Sauer, 1999; Olyott et al., 2006; Roel et al., 2000; Sauer & Lipinski, 1990; Sauer, 1995; Sauer et al., 1992, 1999), life cycle (Augustyn, 1990, 1991; Olyott et al. 2007; Roberts & Sauer, 1994), feeding on the spawning grounds (Augustyn, 1990; Sauer & Lipinski, 1991; Sauer & Smale, 1991, 1993; Sauer et al., 1992), spawning behaviour (Hanlon et al, 1994, 2002; Sauer, 1995; Sauer & Smale, 1993; Sauer et al. 1992, 1993, 1997; Shaw & Sauer, 2004), the inshore spawning environment (Augustyn, 1990; Roberts, 1998, 2002; Roberts & Sauer, 1994; Roberts and van den Berg, 2002; Sauer et al. 1991, 1992), the location of spawning grounds (Augustyn, 1990; Roberts, 1995; Roberts & Sauer, 1994; Sauer, 1995; Sauer et al., 1992, 1993), predation on spawning grounds (Hanlon et al. 2002; Roberts, 1998; Sauer & Smale, 1991, 1993; Smale et al., 1995, 2001), migration / movement on spawning grounds (Augustyn, 1990, 1991; Lipinski et al. 1998; Roberts & Sauer, 1994; Sauer & Smale, 1993) and paralarval development (Oosthuizen & Roberts, 2009; Oosthuizen et al. 2002b; Roberts & van den Berg, 2002; Vidal et al. 2005). A number of these studies have, however, been limited by certain factors. The inshore spawning grounds extend from ~20 to 70 m. Diving observations are only possible up to a depth of 30 m, are limited in terms of the amount of time that can be spent underwater and are highly dependent on water visibility. Many of these limitations can be overcome by the use of underwater cameras, however, the issue of water visibility remains. Not only has the