Search

Northern abalone are an important component of the intertidal and subtidal ecosystems of the Pacific Coast. This research was carried out to test the feasibility of utilizing underwater stereo-camera technology to conduct surveys to estimate the abundance and size structure of northern abalone populations. Consistent with other studies, depth and substrate both impacted the density and length of northern abalone, and provided a basis for implementing stratification strategies for density estimation. The average deployment took about 18 min and resulted in 47 useable image quadrats. The estimated time to analyze each frame was about 3 min, translating into ∼2.5 h of processing time per deployment. The precision of the resulting density estimates was high (relative error ∼0.22–0.37 depending on the method used for stratification) and could be improved by increasing the number of study sites to 35 or greater. The pooled density of northern abalone was estimated as 1.07 individuals/ m–2 (SE = 0.21) and the mean length of northern abalone across the study sites was 67.7 mm (SE = 0.08). Future stereo-camera surveys could be used as a cost-effective supplement to self-contained underwater breathing apparatus diver surveys to increase the precision of abundance and size estimates of northern abalone populations.

In the abalone and Candidatus Xenohaliotis californiensis (Ca. Xc) system, the Ca. Xc bacterium infects abalone digestive tissues and leads to extreme starvation and a characteristic "withering" of the gastropod foot. First identified in black abalone in California after an El Nino event, withering syndrome (WS) has caused large declines in wild black and captive white abalone on the northeastern Pacific coast, but disease resistance levels are species-, and possibly population-specific. This study compared gene expression patterns in the digestive gland of Ca. Xc-exposed and unexposed (control) Pinto abalone (Haliotis kamtschatkana), a particularly susceptible species. Lab-induced Ca. Xc infections were followed over 7 months and RNAseq was used to identify differential gene expression. Exposed Pinto abalone showed distinct changes in expression of 68 genes at 3 and 7 months post-infection relative to those in control animals. Upregulation of an orexin-like receptor (which is involved in feeding signaling) and a zinc peptidase-like region (many amino peptidases are zinc peptidases) in animals infected for 7 months indicates that animals with Ca. Xc infection may be starving and upregulating processes associated with feeding and digestion. Other groups of differentially expressed genes (DEGs) were upregulated or downregulated across control and exposed individuals over the 7-month experiment, including DEG groups that likely correspond to early disease state and to general stress response of being held in captivity. No patterns emerged in genes known to be involved in molluscan immune response, despite this being an expectation during a 7-month infection; digestion-related genes and unannotated DEGs were identified as targets for future research on potential immune response to WS in abalone.

Pinto abalone (Haliotis kamtschatkana), the widest ranging abalone species in North America, occurs from Alaska, United States to Central Baja California, Mexico. The species has been observed in intertidal and subtidal habitats from 0 to 40mdepth. The best available data indicate that pinto abalone abundance has declined in many areas throughout the species' range due to fisheries harvest. Subsistence and personal use fisheries in Alaska and a commercial fishery in Mexico persist. Preliminary data from 2008 to 2016 indicate signs of recovery for some pinto abalone populations along the British Columbia coast due to multiple contributing factors including a reduction in illegal harvest, natural recovery following fishery closure, and low predation pressure. By contrast, pinto abalone populations at the San Juan Islands in Washington are experiencing recruitment failure and continuing to decline, despite closure of the fisheries and no evidence of poaching. Throughout the remainder of the species' range, trends are less clear, due to the lack of regular, long-term monitoring surveys for pinto abalone. The limited data from surveys and/or opportunistic sightings indicate that pinto abalone populations are small, patchily distributed, and/or fluctuate episodically in Alaska, California, and Mexico, with evidence of recent recruitment in a number of locations within these three areas. Baseline abundance and trend data for the species before the advent of commercial fisheries and, in some areas, the local extirpation of sea otters is lacking. Without a clear baseline with which to compare the current abundance levels and trend information, it is difficult to interpret what these levels mean for the status and viability of the species. Threats to pinto abalone were evaluated and characterized using a qualitative rating (i.e., low, moderate, high, very high) based on the threats' scope, severity, and persistence and the sufficiency of the data to support the rating. Several threats that posed a moderate level of risk to pinto abalone were identified including the following: low densities as a result of historical overfishing; the potential threat posed by ocean acidification; and illegal take because of poaching and inadequate law enforcement. The overall risk that pinto abalone face throughout their range was evaluated, and it was determined that they have a low to moderate level of extinction risk now and in the foreseeable future (over both the 30-y and 100-y time horizons). There is a high level of uncertainty regarding demographic factors, in particular regarding whether abundance and productivity levels are sufficient to support the persistence and recovery of the species in the face of continuing and potential future threats. Although recruitment failure may be occurring in some areas (e.g., San Juan Islands Archipelago), in other areas throughout the range recurring and/or recent recruitment events have been observed, despite low densities, and have even resulted in increased densities (across all size classes) at several index sites in British Columbia. Limitations in using demographic data to guide conservation actions and help ensure species persistence could be overcome by conducting consistent monitoring of pinto abalone populations throughout their range.

Population declines in wild and cultured abalones (Haliotis spp.) due to a bacterial disease called withering syndrome (WS) have been documented along the northeastern Pacific Ocean. However, observed differences in species susceptibility to the disease are not well understood. Here, we examined the susceptibility of three temperate abalone species, the cool water (4–14 °C) pinto or northern abalone (Haliotis kamtschatkana), the intermediate water (8–18 °C) red abalone (H. rufescens), and the warm water (12–23 °C) pink abalone (H. corrugata), to experimental WS infection at temperatures facilitating disease proliferation. Mortality data paired with histological and molecular detection of the WS pathogen confirmed that these abalone species exhibit different levels of susceptibility to infection and resistance to WS development ranging from high susceptibility and low resistance in pinto abalone to moderate/low susceptibility and resistance in red and pink abalones. The temperature associated with WS induced mortalities also varied among species: pinto abalone died at the lowest experimental temperature (17.32 ± 0.09 °C), while red abalone died at an intermediate temperature (17.96 ± 0.16 °C), and pink abalone required the highest temperature (18.84 ± 0.16 °C). When data from the current and previous studies were examined, susceptibility to WS was inversely related to phylogenetic distance from white abalone (H. sorenseni), which had the highest susceptibility and lowest resistance of all abalone species tested prior to the current study. These results provide further evidence that an abalone’s thermal optima and phylogenetic relationship can determine its susceptibility to WS; species with cool water evolutionary histories are most susceptible to WS and the most susceptible species appear to be closely related. Differences among the thermal ranges of abalone species have broad implications for WS disease dynamics and highlight the importance of understanding the mechanisms governing the abalone-WS relationship in order to properly manage declining abalone populations.

Haliotis kamtschatkana is the only abalone native to the Pacific Northwest of North America. Haliotis kamtschatkana populations are in decline, and current restoration efforts in Washington State rely on out-planting hatchery-produced juveniles. Hatchery personnel report highest mortalities in the postlarval stage of H. kamtschatkana, mainly during the first 3 to 6 months. Postlarvae feed on films of benthic diatoms, and the purpose of this study was to test six diatom species (Achnanthes brevipes, Amphora salina, Amphiprora paludosa, Cylindrotheca closterium, Navicula incerta, and Nitzschia laevis) as suitable diets for H. kamtschatkana. Diatom diet suitability might rely on several factors, including diatom characteristics as well as the postlarva's ability to ingest the diatoms. The radula is a crucial feeding structure for gastropods and may display morphological plasticity, but this has never been characterized in H. kamtschatkana. We investigated survival, growth, and radula morphology of H. kamtschatkana postlarvae when fed one of six benthic diatom species for 61 days post-settlement. Amphora salina yielded the highest survival, in a statistically homogenous subgroup with N. incerta, A. paludosa, and C. closterium. Achnanthes brevipes yielded exceptionally low survival, on par with a starvation control. Cylindrotheca closterium yielded significantly better growth than all other diets except A. salina. Radula development was similar to that of other abalone species. The shape and size of the radula did not explain success or failure of any of the diatom diets since the radula morphology of H. kamtschatkana was comparable to other abalone that have succeeded when fed these same diets. We found no relationship between diatom diet and radula morphology. We recommend A. salina as a suitable diet for newly settled H. kamtschatkana postlarvae, and that a combination of A. salina and C. closterium be used to supplement feeding on naturally occurring biofilms.

Pinto abalone populations in Washington state have declined precipitously in the last few decades, despite closure of the fishery. Local restoration efforts have focused on outplanting juvenile abalone, which is costly because of the husbandry required to raise abalone to outplanting size. This study tested if hatchery-produced larval pinto abalone could be successfully outplanted and if postoutplant growth of larval abalone differed from hatchery-raised animals. Wild broodstock were spawned, and some larvae remained at the hatchery for rearing, whereas most were transported to the Shannon Point Marine Center (SPMC) for outplanting. At two sites in the Salish Sea, larvae were outplanted at a density of 13,000 larvae m–2 into two types of larval abalone modules (LAM): tented LAM (125 µm Nitex tenting) and open LAM (no tenting). There were also control LAM with no tenting and no abalone. Larvae were also seeded in LAM in aquaria at SPMC to compare field and aquaria survival and to estimate emigration. Shell lengths of field, laboratory, and hatchery-reared abalone were measured to better understand if hatchery life compromises early growth. Four months after outplanting, abundance of settled abalone was significantly greater in tented LAM than open and control LAM. Control LAM contained no abalone, suggesting reproduction by wild abalone did not occur at the field sites. Open LAM had a mean outplant success of 0.1% (0–12 settled abalone) and tented LAM a mean success of 0.4% (16–35 settled abalone). Outplant success was higher in SPMC aquaria. Open and tented LAM had 1.5% and 3.0% success, respectively. Abalone found on aquaria walls outside the LAM accounted for 0.2% of the seeded abalone for both open and tented LAM. Four months after outplanting, shell lengths of field abalone were not significantly different from lengths of hatchery-reared abalone, suggesting hatchery conditions did not compromise growth rates of newly settled abalone. These findings suggest that releasing larval pinto abalone into tented field modules has potential to supplement wild stocks in the Salish Sea as a lower cost alternative to outplanting juveniles.

I used light and electron microscopy to investigate shell-attached muscles in larvae of Haliotis kamtschatkana Jonas, 1845, because an early description of these muscles in H. tuberculata by Crofts (1937, 1955) has featured prominently in theories about gastropod evolution. Larval shell muscles in H. kamtschatkana can be grouped into two categories. The first category consists of the larval retractor muscle (LRM) and the accessory larval retractor muscle (ACC); these are striated muscles in which myofilaments begin differentiating before the head and foot rotate relative to the protoconch (this rotation is known as ontogenetic torsion). Collectively, these muscles ultimately insert on tissues within the larval head and mantle, but the ACC and mantle fibers of the LRM degenerate as metamorphic competence is achieved. The second category consists of two nonstriated pedal muscles that differentiate after cephalopodial rotation. The left pedal muscle is anchored on the back of the protoconch, to the left of the shell-attachment plaque for the LRM. It projects into the foot primarily, but also gives rise to muscle slips extending into the mantle fold. The right pedal muscle is anchored on a calcareous septum secreted along the visceral rim of the protoconch. The new data force a reconsideration of the ancestral homologues of larval shell muscles in abalone, because Crofts may have misidentified the accessory larval retractor muscle as a precursor of one of the later pedal muscles.

Nearshore kelp forest ecosystems are highly vulnerable to climate change and ocean warming, which can alter community dynamics and change the trajectory of species recovery in unpredictable ways. Abalone (Haliotis spp.) populations in the Southern California Bight (SCB) are still recovering from a combination of overfishing and disease, despite the closure of the fisheries 20 years ago and active restoration programs for abalone species in the region. For this study, abalone recruitment and sea urchin populations were surveyed in artificial habitats (16–22 m) across a spatial and temporal climatic gradient in southern California from 2010 to 2017 to inform the development of climate-ready abalone restoration programs. The SCB encompasses warm and cool islands, and experienced two periods of ocean conditions—cool (2010–2013) and warm ocean conditions (2014–2016). Dive surveys of the artificial habitats revealed that juvenile abalone recruitment remained low during the study period, suggesting that recovery is slow. Warm-water years favored recruitment of juvenile pink (Haliotis corrugata) and green abalone (Haliotis fulgens), with the highest abalone recruitment observed at Catalina Island. Endangered white abalone (Haliotis sorenseni) were not observed despite placing the artificial habitats in suitable deep rocky reefs, which is further evidence supporting their endangered species status. The coolest site, San Diego, had little abalone recruitment, with a few juvenile red abalone (Haliotis rufescens) and threaded (Haliotis kamtschatkana) abalone present. Sea urchin abundance and diversity increased during the warm period, with the largest increase at Catalina Island. During the warm period, Coronado sea urchin (Centrostephanus coronatus) increased in abundance, coincident with a decrease in the commercially valuable temperate red sea urchin (Mesocentrotus franciscanus). Potential shifts in the sea urchin assemblage to warm-water sea urchins may negatively impact recovering abalone populations and the red sea urchin fishery. Climate-ready abalone restoration will require ecosystem-based monitoring, tracking on not only abalone recruitment but also sea urchins, algal abundances, ocean temperature, and kelp forest communities as climate change may lead to complex and unexpected ecosystem interactions.

We documented the diet of the Black Oystercatcher (Haematopus bachmani) on Haida Gwaii, British Columbia, Canada, (2004–2010) with prey remains from 99 territories in Gwaii Haanas National Park Reserve, National Marine Conservation Area Reserve and Haida Heritage Site. The ranking of its four main prey types did not vary annually. Numerically, the prey comprised 50–75% limpets, 14–34% mussels, 8–18% chitons, 1–2% Northern Abalone (Haliotis kamtschatkana), and

Hatchery-reared abalone outplanted into the wild at higher than ambient densities often experience very high levels of mortality as a result of density-dependent predation by natural predators. We conducted 2 experiments to assess the effectiveness of different methods of reducing predation on outplanted northern abalone (Haliotis kamtschatkana). During the first experiment, we removed small predators from brick-filled habitat cages that excluded large predators. The survival rates of juvenile abalone (mean shell length (SL), 22 mm) were greater in cages from which sea stars and other predators were removed periodically than in control cages. During the second experiment, we constructed 30 fenced 1 -m2 outplanting plots and assigned 10 randomly to be controls and 20 to be filled with 1 of 4 complex substrates (0.3-m layer of cobbles, 0.3-m layer of boulders, 0.9-m layer of cobbles, and 0.9-m layer of boulders). We then released 30 large juvenile abalone (mean SL, 51.5 mm) into each plot. The numb...

Northern abalone (Haliotis kamtschatkana) in British Columbia, Canada, are listed as endangered and are protected from fishing, yet their populations continue to decline. It is suspected that supplementation of wild populations with hatchery-reared abalone will be necessary for the recovery of this species. This study examines the magnitude, timing, and causes of post-outplanting mortality of hatchery-reared late-juvenile northern abalone. Abalone survivorship declined precipitously following outplanting, with 83% of abalone surviving 24 h after release and only 34% surviving 2 weeks in the wild. Handling, tagging, and temperature variations experienced during the outplanting procedure did not cause mortality. The majority of the abalone mortality in this study was attributable to predators. Additional factors accounted for only 1–2% mortality over 7 d. A 1-week acclimatization period within predator exclosures did not improve subsequent survival of outplants. These results demonstrate that the ouplanting of hatchery-reared abalone as a method of restoring wild populations of this endangered species is primarily constrained by high mortality during the first few days after outplanting, and that almost all of this early mortality is caused by predation. Predation mortality will therefore have to be overcome if outplanting of hatchery-reared juvenile abalone is to be an effective restoration strategy. Copyright © 2013 John Wiley & Sons, Ltd.

Managing for simultaneous recovery of interacting species, particularly top predators and their prey, is a longstanding challenge in applied ecology and conservation. The effects of sea otters (Enhydra lutris kenyoni) on abalone (Haliotis spp.) is a salient example along North America's west coast where sea otters are recovering from 18th‐ and 19th‐century fur trade while efforts are being made to recover abalone from more recent overfishing. To understand the direct and indirect effects of sea otters on northern abalone (H. kamtschatkana) and the relative influence of biotic and abiotic conditions, we surveyed subtidal rocky reef sites varying in otter occupation time in three regions of British Columbia, Canada. Sites occupied by sea otters for over 30 years had 16 times lower densities of exposed abalone than sites where otters have yet to recover (0.46 ± 0.08/20 m2 vs. 7.56 ± 0.98/20 m2), but they also had higher densities of cryptic abalone (2.17 ± 1.31/20 m2 vs. 1.31 ± 0.20/20 m2). Abalone densities were greater in deeper vs. shallower habitats at sites with sea otters compared to sites without otters. Sea otter effects on exposed abalone density were three times greater in magnitude than those of any other factor, whereas substrate and wave exposure effects on cryptic abalone were six times greater than those of sea otters. While higher substrate complexity may benefit abalone by providing refugia from sea otter predation, laboratory experiments revealed that it may also lead to higher capture efficiency by sunflower stars (Pycnopodia helianthoides), a ubiquitous mesopredator, compared to habitat with lower complexity. Sea otter recovery indirectly benefitted abalone by decreasing biomass of predatory sunflower stars and competitive grazing sea urchins, while increasing stipe density and depth of kelp that provides food and protective habitat. Importantly, abalone persisted in the face of sea otter recovery, albeit at lower densities of smaller and more cryptic individuals. We provide empirical evidence of how complex ecological interactions influence the effects of recovering predators on their recovering prey. This ecosystem‐based understanding can inform conservation trade‐offs when balancing multifaceted ecological, cultural, and socio‐economic objectives for species at risk.

Since 1969, abalone populations have declined globally more than 50%, with many species now recognized as threatened, endangered, or species of concern. As monitoring progresses and restoration efforts evolve to include population supplementation, a reliable and robust method of tagging individual abalone is needed. Current abalone tagging methods are unsatisfactory, particularly for long-term studies as a result of tag loss, shell erosion, and encrustation. Observing tag numbers of cryptically positioned abalone can be difficult. To obviate these issues, we evaluated passive integrated transponders (PITs) as tags for pinto abalone (Haliotis kamtschatkana kamtschatkana). We applied 9-mm PITs with cyanoacrylate glue to the dorsal exterior of the shell and to the ventral anterior of the shell, and by injection into the foot muscle of small adults (trial 1), and applied PITs to the ventral anterior of the shell of juveniles (trial 2). We subsequently tracked growth, survival, and tag retention over 15 mo in trial 1 and 6 mo in trial 2 in captivity. Among small adults (trial 1), differences in relative growth rate and survival were not significant. PIT retention by adhesion to the ventral anterior and dorsal exterior was significantly greater than injection into the foot in trial 1. Between controls and tagged animals in trial 2, differences in survival were not significant. There was no significant difference in ventral anterior tag retention between trial 1 and trial 2. Gluing PITs on the ventral anterior of the shell is a promising method because abalone quickly formed nacre over the tags, incorporating them into the shell, which does not appear to affect tag detection by the PIT reader. Trials are underway to characterize PIT retention in natural habitats, to determine tag longevity, and to use PITs to track adults reintroduced to aggregations.

The restoration of abalone (Haliotis spp.) populations through supplementation with the offspring of hatchery-spawned wild parents has been attempted in several species, with variable results. Between 2002 and 2005, the Bamfield Huu-ay-aht Community Abalone Project released 4.5 million larvae and 152,000 juveniles of the northern abalone (Haliotis kamtschatkana) into Barkley Sound, BC. The purpose of this study was to estimate the long-term survival of outplanted abalone 3–7 years after their release and thus determine their contribution to local population densities at three different outplanting sites. We identified outplanted abalone by genotyping epipodal tentacles sampled from wild-caught abalone for seven microsatellite loci. We then used three different pedigree reconstruction programs: one that used genotypes from hatchery-reared siblings (pedigree 2.2), one that used the wild parent genotypes that were available (cervus 3.0), and one that used both sources of information (colony 2.0). Each program identified different but partially overlapping subsets of hatchery-outplanted offspring. From this we inferred that up to 26% of the individuals sampled at the main outplanting site were from hatchery spawnings. Despite this large contribution of hatchery-reared stock, the density of mature abalone at each site was below the level required for successful fertilization. More intensive outplanting efforts might increase population densities of this broadcast spawner above this minimum sustainable level. However, for supplementation to be successful, other factors that could reduce outplanted juvenile survival, including the low genetic diversity of hatchery-produced offspring and the low habitat quality of some outplanting sites, need to be monitored.

To 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 recr...

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...

Northern abalone (Haliotis kamtschatkana kamtschatkana) is a federally listed species of concern. The status of northern abalone and the characteristics of the habitats they associate with were determined showing that northern abalone have declined dramatically in Washington State with present day abundances

Abalone species are different from most mollusks utilized in aquaculture as they are known to hybridize in laboratory-induced matings. Allotriploidization of hybrid abalone has not yet been studied, and methodology useful in verifying the genotypic condition of such allotriploids do not exist. Genotypic verification of hybridization and allotriploidization in a cross of Haliotis fulgens and Haliotis rufescens was performed utilizing 6 crossamplifying microsatellite loci. Five H. rufescens spawns were used in this experiment, dividing each spawn into control and experimental hybrid groups and further into diploids and triploids. Two microsatellite loci developed for H. fulgens and H. rufescens allowed for the genotypic identification of hybrids within diploid and triploids. To further verify the percentage of allotriploids within the genotypic hybrids in the triploid hybrid groups, microsatellite loci originally developed in Haliotis corrugata and Haliotis kamtschatkana were tested for crossamplification in H. fulgens and H. rufescens. Of 21 loci, 4 were chosen for this study based on their crossamplification, heterozygosity in the females, and centromere recombination frequencies. Allotriploids in triploid-hybrid larvae were then detected by identifying larvae with recombinant genotypes at any of those loci. One family had low success verification associated with reduced recombination frequencies for all loci in that family. These results demonstrate that allotriploid verification at larval stages is feasible but depends on the number of loci available, their crossamplification in the species, and their recombination frequencies.

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.

Bayesian hierarchical models were developed to estimate the growth parameters of northern abalone, Haliotis kamtschatkana, using tag-recapture data with a mixture of single and multiple recaptures. Individual variability in the growth parameters L∞ and k of the von Bertalanffy model was incorporated in the analyses. The models developed fit the data well based on the Bayesian p-values. Variability in L∞ for individuals was high relative to the variability in L∞ for the population, and variability in k for individuals was about the same as the variability in k for the population. Simulations showed that estimates of the growth parameters were accurate (relative biases

Pinto abalone ( Haliotis kamtschatkana kamtschatkana ) index stations in the San Juan Archipelago were systematically monitored by the Washington Department of Fish and Wildlife from 1992 through 2006. During this period, abalone abundance declined by 77% and the mean shell length (SL) increased 10.4 mm. Abalone densities at all index stations are currently well below the threshold of 0.15 abalone·m–2 required for successful fertilization. From 1992 to 1996, 16% of individuals encountered measured 114 mm SL was greater in the 2000s than in the 1990s. The mean SL of all live abalone observed in the 1990s (107.62 ± 0.87 mm) was significantly different from the mean SL of empty shells (114.21 ± 2.1 mm), but no difference was detected between the mean SLs of empty shells and live abalone in the 2000s (114.97 ± 1.42 mm). Taken together, these data suggest recruitment failure from an Allee response to low population densities.

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

Growth of abalone in the wild and hatchery is density-dependent in response to intraspecific competition for food and/or space. To determine if a candidate aquaculture species, Haliotis kamtschatkana, exhibits density-dependent growth we raised animals at three density levels and two food treatments: unlimited (ad libitum) and rationed (individual portions were the same among density treatments). We also tested for differences in food consumption, foraging patterns and stacking behaviour among the density levels. We observed density-dependent growth in the rationed treatments, indicating that relatively high growth rates at lower densities are driven, in part, by factors other than differences in food consumption. However, overall the quantity of food consumed related directly to growth; treatments fed ad libitum had higher growth rates. Furthermore, even when food was provided in excess, foraging was restricted to ~ 2 h after sunset in all treatments and the amount consumed per abalone was significantly lower at high densities. This is probably because high density animals could not access the food provided: fewer were observed foraging and they had to move from prominent stacks. Our results indicate that both temporal and spatial access to food are critical and that managers can observe foraging and stacking by abalone in tanks to determine if a specific design will limit food consumption, and ultimately growth.

The northern abalone, Haliotis kamtschatkana, fisheries in British Columbia (BC) were closed in 1990 because of substantial declines in the stock biomass. Abalone biomass has remained low since the fishery closure. We used abalone survey data and established growth models to study the stock-recruitment (SR) relationships, estimate mortality rates, and simulate population growth trajectories at various mortality levels for abalone populations in the Queen Charlotte Islands and the Central Coast of BC. The fitted SR curves were flat and near linear, indicating a lack of productivity in the abalone populations. At low spawning stock biomass (

The northern abalone is listed as threatened under the Canadian Species at Risk Act. Northern abalone occur in a wide range of habitats from fairly sheltered bays to exposed coastlines. However, not all habitats are likely to support high abalone densities with large northern abalone that have high fecundity. Therefore, habitats that can support dense concentrations of large abalone would be better suited for aggregation rebuilding projects. Several experimental rebuilding projects are currently underway; the experimental sites were, in general, selected based on abalone presence and relative abundance. This study attempts to describe abalone habitat suitable for rebuilding efforts by using data from surveys completed at the start of the large decline of abalone densities observed in British Columbia (BC). Several areas were surveyed to determine abalone density on the southeast coast of the Queen Charlotte Islands and the north central mainland coast of BC between 1978 and 1980. Habitat data were recorded after each dive, including substrate types and dominant algae cover and species. Four categories of algal types were analyzed based on height and growth patterns: (1) canopy; (2) understorey (large bottom cover); (3) turf (short bottom cover); and (4) encrusting. In addition, an index of wave exposure was also calculated for each site surveyed. Northern abalone density was inversely correlated to mean abalone shell lengths. The exposure index was correlated positively to abalone density but negatively to mean shell length. Regression tree classifications successfully separated habitats of high and low abalone densities, but these differed from habitats classified using mean shell length as the response variable. To optimize rebuilding efforts, a compromise between the two classification models, one with density as the response variable and the other with mean shell length, may have to be developed.

SUMMARY Crossing of the pleurovisceral nerve cords in gastropods has supported the view that gastropods evolved by 180° rotation between the ventral and dorsal body regions. Indeed, a rotation of this type occurs as a dramatic morphogenetic movement (“ontogenetic torsion”) during the development of basal gastropods. According to a long-standing hypothesis, ontogenetic torsion in basal gastropods preserves an ancient developmental aberration that generated the contorted gastropod body plan. It follows from this reasoning that crossing of the pleurovisceral nerve cords during gastropod development should be mechanically coupled to ontogenetic torsion. The predicted mechanical coupling can now be examined because of the discovery of an early differentiating neuron in Haliotis kamtschatkana (Vetigastropoda) that expresses 5-hydroxytryptamine-like immunoreactivity. The neuron appeared to delineate the trajectory of the pleurovisceral nerve cords beginning before ontogenetic torsion. Before torsion, the neuronal soma is embedded in mantle epithelium at the ventral midline and two neurites extend anteriorly toward the apical sensory organ. Contrary to expectation, the two neurites of this cell did not cross-over during ontogenetic torsion because the soma of this mantle neuron shifted in the same direction as the rotating head and foot. Full crossing of the pleurovisceral nerve cords occurred gradually during later development as the mantle cavity deepened and expanded leftward. These results are consistent with a generalization emerging from comparative studies indicating a conserved developmental stage for gastropods in which the mantle cavity is localized to one side, despite a fully “post-torsional” orientation for other body components. Developmental morphology before this stage is much more variable among different gastropod clades.

Marine invertebrate species have usually been overlooked in favor of high-profile vertebrate species for facilitating dialogue towards area conservation. The northern abalone (Haliotis kamtschatkana) is proposed as a focal ("flagship") species whose protection and recovery could concentrate public concern for abalone and its associated kelp forest ecosystems in Haida Gwaii (Queen Charlotte Islands), British Columbia. I explain how issues of culture, commerce, and conservation unite to create a strong role for northern abalone in preparations for creating a large marine conservation area within Haida Gwaii. Culture is relevant, as local indigenous people (the Haida) are currently denied access to constitutionally established subsistence fishing rights for northern abalone. Commerce is involved as ongoing kelp forest-associated fisheries co-occur with northern abalone. Finally, this is a challenging precedent in Canadian marine conservation, as restoring two "listed" species- at risk (northern abalone and t...

We describe a method for preparation and maintenance of isolated digestive-gland cells in the abalone, Haliotis kamtschatkana. Viability of the isolated cells was confirmed by the fact that 18 h after preparation the cells exhibited less than 5% staining with trypan blue and actively synthesized glycogen following the addition of glucose substrate. Use of the method in a 15-month study of metabolic activity of the digestive gland of H. kamtschatkana showed significant differences in oxygen consumption of isolated-cell preparations correlated with seasonal differences in somatic and gametogenetic growth, and with relative size of the digestive gland.

A combination of laboratory and field experiments with the commercial abalone species Haliotis laevigata showed that fertilization may be a limiting factor in some exploited populations when distances separating spawning individuals are too large. The effects of gamete age, gamete concentration, and gamete contact time in the laboratory were used to model fertilization success in situ and compared with experimental fertilization rates in the field. Highest fertilization rates in vitro (80%) were found for sperm concentrations in the range of 1 × 104 to 1 × 106·mL-1. Fertilization rates of 48 ± 1.7% (95% CI) were measured at separation distances of 2 m and dropped to 2.8 ± 0.7% (95% CI) at 16 m downstream, agreeing closely with rates predicted by the model. Recruitment failures reported for South Australian populations of H. laevigata have occurred when densities fell below ca.0.3 animals·m-2, or mean nearest-neighbor distances between 1 and 2 m. This density corresponds well to critical nearest-neighbor distances for fertilization success. Stocks at higher densities are predicted to have higher fertilization rates (ca.90%) such that fertilization success is not a factor limiting recruitment.

Marine reserves have been suggested as tools for assisting the management of fisheries by protect- ing vulnerable marine species from overexploitation. Although there is a theoretical basis for believing that marine reserves may serve as management tools, there are few marine reserves in the world in which to test their effectiveness. My research evaluated three forms of marine reserve on the south coast of Vancouver Is- land, British Columbia, Canada. I used northern abalone ( Haliotis kamtschatkana ), a severely depleted shell- fish in this region, as an indicator of the effectiveness of the reserves. Abalone populations in eight sites re- ceiving different degrees of spatial protection were counted and measured in situ during the spring of 1996 and 1997. In all sites with enforced harvest closures, populations of abalone were greater, and one site with nearly 40 years of protection had on average much larger (older) abalone. Reproductive output, as a func- tion of abundance and size, was also greater in the enforced reserve areas. Larval dispersal from reserves, and hence the benefit to exploited areas, was not formally surveyed. Nevertheless, the results of my study, combined with knowledge of present abalone populations, life history, and regional hydrodynamics, suggest that establishment of reserves is justified in the absence of perfect knowledge of larval dispersal.