Abalone Haliotis Kamtschatkana Research Articles

Predicting the optimal amount of time to spend learning before designating protected habitat for threatened species

Abstract Deciding when to protect threatened species habitat when complete knowledge about the habitat extent is uncertain is a common problem in conservation. More accurate habitat mapping improves conservation outcomes once that habitat is protected. However, delaying protection to improve accuracy can lead to species decline or, at worst, local extinction when threats to that habitat continue unabated before protection is implemented. Hence, there is a trade‐off between gaining knowledge and taking conservation action. We quantified this trade‐off and determined the optimal time to spend learning about a species' habitat before protecting that habitat. We used a range of hypothetical learning curves to model improvements in the accuracy of predicted habitat over time, and receiver operating characteristic (ROC) curves to model the corresponding increase in the proportion of habitat protected. We used rates of habitat loss to model the impact of delaying habitat protection and derived analytical solutions to the problem for different types of learning curves. We illustrate our approach using two threatened species, the koala Phascolarctos cinereus in Australia and northern abalone Haliotis kamtschatkana in Canada. Our approach confirms that when impacts of threatening processes are incurred rapidly, the need for timely protection is high, and the optimal time to spend learning is short for all learning curves. When the rate of habitat loss is low, we benefit from better habitat identification, and the optimal time to protect is sensitive to assumptions about how we learn and the proportion of non‐habitat we are willing to protect unnecessarily. Navigating the trade‐off between information gain and timely action is a common problem in conservation. By optimizing the trade‐off between the benefits of improving mapping accuracy and the costs of delaying protection, we provide guidelines on the effective allocation of resources between habitat identification and habitat protection. Importantly, by explicitly modelling this trade‐off with a range of learning curves and estimates of the rates of habitat loss or other threatening processes, we can predict the optimal time to spend learning even when relatively little is known about a species and its habitat.

Low Juvenile Pinto Abalone Haliotis kamtschatkana kamtschatkana Abundance in the San Juan Archipelago, Washington State

AbstractTo investigate contemporary pinto abalone Haliotis kamtschatkana kamtschatkana recruitment events and juvenile abundance, 66 abalone recruitment modules (ARMs) were deployed at two depths and three sites in the San Juan Archipelago (Washington State) that were historically inhabited by substantial abalone populations. Based on published studies from California and British Columbia, ARMs are proven tools for surveying juvenile pinto abalone abundance. Abalone recruitment modules provide complex habitat and protection from predation. The ARMs were surveyed in situ for juvenile abalone abundance six times over the course of 26 months. Only eight abalones were observed, including three juveniles that were less than 50 mm (shell length). The mean density of juvenile abalones inhabiting the ARMs across all three sites during the 2006 surveys was 0.012/m2. The absence of juvenile abalones within the ARMs, combined with sharp regional declines in adult pinto abalone abundance, suggests limited local recruitment of this species, which is currently designated as threatened in Canada and as a species of concern in the USA.

Aggregation of the Northern AbaloneHaliotis kamtschatkanawith Respect to Sex and Spawning Condition

ABSTRACT Current low densities of the northern abalone Haliotis kamtschatkana may be affecting the fertilization success of this endangered broadcast spawner, thus preventing its populations from recovering to historical levels. This study attempted to determine whether the northern abalone were significantly aggregated during the period just before spawning because this may compensate in part for their low densities. We used scuba to map the spatial distribution, sex, and spawning condition of tagged abalone within grids at three different sites close to Bamfield Marine Sciences Center on the west coast of Canada. Underwater tagging methods were then used to monitor individuals over a 3-wk period during the 2009 spawning season. We found that the populations at all sites had nearest neighbor R ratios significantly less than 1.0, which indicates an aggregated distribution. Within the range of densities observed for our 3 sites (0.12-0.64 adults/m2), the mean distances to the nearest neighbor (1) of either...

Occurrence of the Red AbaloneHaliotis rufescensin British Columbia, Canada

Abstract: We document the first occurrence of a live red abalone, Haliotis rufescens Swainson, 1822, found on the central coast of British Columbia. The initial identification was based on morphological characteristics. Previously, the northern or “pinto” abalone Haliotis kamtschatkana kamtschatkana Jonas, 1845 has been the only abalone species considered to naturally occur in the coastal waters of British Columbia. Since hybridization of H. kamtschatkana with H. rufescens was known to occur, genetic analysis of tissue samples was undertaken to confirm the morphological identification as a purebred red abalone.

Ontogenetic shift in susceptibility to predators in juvenile northern abalone, Haliotis kamtschatkana

Predation has been suggested as a major cause of juvenile mortality in benthic marine invertebrates. However, the extent to which juveniles are susceptible to predators is unknown for most species, and it remains unclear to what extent ontogenetic shifts in susceptibility to predators are common among marine invertebrates. This study examined the northern abalone Haliotis kamtschatkana, a species listed as threatened in British Columbia, Canada. Our goals were to characterize the diversity and abundance of species that prey on juvenile abalone and determine if abalone experience an ontogenetic shift in susceptibility to predators. Juvenile H. kamtschatkana were found to be susceptible to a broad variety of predators: 14 of the 37 potential predator species to which we offered juvenile abalone (≤ 28 mm shell length (SL)) consumed at least one juvenile abalone. Four of those species (three crabs and one seastar) consumed ≥ 10% of the juvenile abalone that were offered in the laboratory. These species were present at field sites where abalone are found, indicating that they have the potential to be significant predators of juvenile H. kamtschatkana in the wild. The most abundant predators were small crabs, especially Lophopanopeus bellus (black-clawed crabs) and Scyra acutifrons (sharp-nosed crabs). Juvenile H. kamtschatkana also experienced a pronounced ontogenetic shift in susceptibility to predators. The risk of predation for juvenile H. kamtschatkana decreased rapidly with increasing body size, especially over the 12–13 mm SL size range. Susceptibility remained low beyond 13 mm SL, indicating relatively low and unchanging levels of predation risk once the individual reaches this size. Although abalone are susceptible to several species during the first 1–2 years of life, predator effects on juvenile abalone abundance and microhabitat use may largely be attributable to the influence of only 1 or 2 predator species that can only kill abalone < 13 mm SL.

The contribution of anaerobic energy to gastropod crawling and a re-estimation of minimum cost of transport in the abalone, Haliotis kamtschatkana (Jonas)

The contribution of anaerobic metabolism to the minimum cost of transport (COT min; energy required to transport a unit mass over a unit distance, excluding maintenance and postural costs) was determined for the abalone Haliotis kamtschatkana. Abalone were induced to crawl in water for 6 m at speeds up to 9.9 shell lengths·min −1. Changes in the concentrations of the anaerobic metabolites tauropine, d-lactate, arginine phosphate, and arginine occurred in foot muscle, but only at speeds at or above five shell lengths·min −1. These metabolites did not change significantly in the shell adductor muscle. The amount of anaerobically derived ATP used during crawling was calculated and the values were compared with data for aerobic ATP production. Anaerobic metabolism accounted for 54% of COT min, and the aerobic COT min estimated by Donovan and Carefoot (1997) [Donovan, D.A., Carefoot, T.H., 1997. Locomotion in the abalone Haliotis kamtschatkana: pedal morphology and cost of transport. J. Exp. Biol. 200, 1145–1153] was thus adjusted from 20.3 J·kg −1 m −1 to 44.1 J·kg −1 m −1. This new value places abalone above the regression line of log 10COT min on log 10mass for running vertebrates, indicating that transport costs for abalone are more expensive than for the average similar-sized runner. The contribution of anaerobic metabolism was also determined for prolonged air exposure and whole animal righting behavior to allow comparisons to be made with other abalone species for which these data, but not data on anaerobic metabolism during crawling, were available in the literature. On this basis, we suggest that in comparison to H. kamtschatkana, Haliotis lamellosa and Haliotis iris may have lower aerobic scopes during crawling, while that of Haliotis asinina may be considerably higher.

Initiation, calcification, and form of larval “archaeogastropod” shells

The coiled shell of gastropods begins as a cap-shaped lens of organic and calcified material that covers the posterior dorsal side of the larva. During development the cap enlarges to cover the larval visceral mass. Marginal growth then produces the characteristic coiled shell. One model of the initiation of shell coiling in “archaeogastropods” requires that the shell remains flexible and uncalcified until after torsion, and that muscle contraction during torsion deforms the shell. We describe early shell calcification and tested this requirement of the model for the patellogastropod limpets Tectura scutum and Lottia digitalis, the trochids Calliostoma ligatum and Margarites pupillus and the abalone Haliotis kamtschatkana. We determined the stage of initial calcification by staining larvae with the fluorescent calcium marker calcein and observing them with bright field, crossed polarizing filter, and fluorescence microscopy. In T. scutum the earliest observable shell was calcified and calcium was sometimes detected even before the initial shell was visible. Larvae of the other species deposited a noncalcified matrix that was subsequently calcified, and in C. ligatum and M. pupillus this initial calcification was distinctly spotty. Shells of both patellogastropods and the abalone were demonstrably rigid prior to torsion while the shells of the trochids were not. These results suggest that shell coiling in patellogastropods and abalone is not initiated by contraction of the larval retractor muscle during torsion; in trochids this mechanism is possible. However, analysis of camera lucida drawings of pre- and post-torsional shells of T. scutum and C. ligatum did not detect shell shape changes during torsion. J. Morphol. 235:77–89, 1998. © 1998 Wiley-Liss, Inc.

Initiation, calcification, and form of larval "archaeogastropod" shells.

The coiled shell of gastropods begins as a cap-shaped lens of organic and calcified material that covers the posterior dorsal side of the larva. During development the cap enlarges to cover the larval visceral mass. Marginal growth then produces the characteristic coiled shell. One model of the initiation of shell coiling in "archaeogastropods" requires that the shell remains flexible and uncalcified until after torsion, and that muscle contraction during torsion deforms the shell. We describe early shell calcification and tested this requirement of the model for the patellogastropod limpets Tectura scutum and Lottia digitalis, the trochids Calliostoma ligatum and Margarites pupillus and the abalone Haliotis kamtschatkana. We determined the stage of initial calcification by staining larvae with the fluorescent calcium marker calcein and observing them with bright field, crossed polarizing filter, and fluorescence microscopy. In T. scutum the earliest observable shell was calcified and calcium was sometimes detected even before the initial shell was visible. Larvae of the other species deposited a noncalcified matrix that was subsequently calcified, and in C. ligatum and M. pupillus this initial calcification was distinctly spotty. Shells of both patellogastropods and the abalone were demonstrably rigid prior to torsion while the shells of the trochids were not. These results suggest that shell coiling in patellogastropods and abalone is not initiated by contraction of the larval retractor muscle during torsion; in trochids this mechanism is possible. However, analysis of camera lucida drawings of pre- and post-torsional shells of T. scutum and C. ligatum did not detect shell shape changes during torsion. J. Morphol. 235:77-89, 1998. © 1998 Wiley-Liss, Inc.

Locomotion in the abalone Haliotis kamtschatkana: pedal morphology and cost of transport

Morphological analyses of pedal sole area and pedal waves were conducted for a range of speeds and body sizes in the abalone Haliotis kamtschatkana. The pedal sole of resting abalone increased in size disproportionately with animal volume (slope of log10-transformed data, b=0.83; expected slope for isometry, b0=0.67) and length (b=2.51; b0=2.0). Pedal wave frequency increased linearly with speed, confirming that abalone increase speed by increasing the velocity of pedal waves. Total area of the pedal sole decreased by 2.1 % for each shell length per minute increase in speed. Likewise, the area of the foot incorporated into pedal waves increased by 1.8 % for each shell length per minute increase in speed. Together, these changes translated into a 50 % decrease in the pedal sole area in contact with the substratum at a maximum escape speed of 15 shell lengths min-1, relative to the pedal sole at rest. The amount of mucus secreted by resting animals during adhesion to the substratum increased isometrically with foot area (slope of log10-transformed data, b=1.08). The amount of mucus secreted during locomotion did not vary with speed, but was less than the amount needed for adhesion. We suggest that these morphological and physiological changes reduce the energy expenditure during locomotion. Cost of transport was investigated for a range of speeds and abalone sizes. The rate of oxygen consumption O2 (in &micro;l O2 g-1 h-1) increased linearly with increasing absolute speed v (in cm min-1): O2=40.1+0.58v-0.15m (r2=0.35, P=0.04), where m is body mass (in g). Minimum cost of transport, calculated from the slope of absolute speed on O2, was 20.3 J kg-1 m-1. Total cost of transport (COTT) and net cost of transport (COTN) were high at low speeds and decreased as speed increased, to minima of 86.0 J kg-1 m-1 and 29.7 J kg-1 m-1, respectively, at speeds measured in the respirometer. Log10-transformation of both cost of transport and speed data yielded linear relationships with the following regression equations: log10COTT=3.35-0.90log10v-0.21log10m (r2=0.89; P<0.006) and log10COTN=2.29-0.69log10v-0.09log10m (r2=0.48; P<0.006), respectively.

GASTROPOD TORSION: A TEST OF GARSTANG'S HYPOTHESIS.

Torsion occurs in gastropod molluscs as a 180° twisting of the shell and viscera relative to the head and foot of the veliger larva. Garstang (1928, 1929) proposed, and it has since become widely accepted, that torsion functions as a larval defense by allowing veligers to first pull the head into the shell, then sealing the aperture with the foot and operculum. However, when we offered pre-torsional and torted larvae of the abalone Haliotis kamtschatkana Jonas as prey to seven planktonic predator species from four phyla, in only one case was rate of predation reduced on torted larvae. It therefore appears that torsion does not function defensively, indicating that other selective pressures probably maintained this trait in primitive gastropods.

Estimation of Abalone Mortality Rates with Growth Analysis

Abstract We describe a maximum-likelihood procedure for obtaining simultaneous estimates of growth and total-mortality rates from size-frequency distributions. The method is applied to size data from simulations and from two populations of northern abalone Haliotis kamtschatkana in British Columbia. Total-mortality-rate estimates varied with the assumed number of age classes and other model variables, but this variation was satisfyingly small. Received May 22, 1982 Accepted February 5, 1983