Kelly S. Andrews

Seasonal and Ontogenetic Changes in Movement Patterns of Sixgill Sharks

Background Understanding movement patterns is fundamental to population and conservation biology. The way an animal moves through its environment influences the dynamics of local populations and will determine how susceptible it is to natural or anthropogenic perturbations. It is of particular interest to understand the patterns of movement for species which are susceptible to human activities (e.g. fishing), or that exert a large influence on community structure, such as sharks. Methodology/Principal Findings We monitored the patterns of movement of 34 sixgill sharks Hexanchus griseus using two large-scale acoustic arrays inside and outside Puget Sound, Washington, USA. Sixgill sharks were residents in Puget Sound for up to at least four years before making large movements out of the estuary. Within Puget Sound, sixgills inhabited sites for several weeks at a time and returned to the same sites annually. Across four years, sixgills had consistent seasonal movements in which they moved to the north from winter to spring and moved to the south from summer to fall. Just prior to leaving Puget Sound, sixgills altered their behavior and moved twice as fast among sites. Nineteen of the thirty-four sixgills were detected leaving Puget Sound for the outer coast. Three of these sharks returned to Puget Sound. Conclusions/Significance For most large marine predators, we have a limited understanding of how they move through their environment, and this clouds our ability to successfully manage their populations and their communities. With detailed movement information, such as that being uncovered with acoustic monitoring, we can begin to quantify the spatial and temporal impacts of large predators within the framework of their ecosystems.

Scale and pattern of broadnose sevengill shark Notorynchus cepedianus movement in estuarine embayments

The detailed movements of 32 acoustically tagged broadnose sevengill shark Notorynchus cepedianus were documented in and around north-east Pacific Ocean estuarine embayments from 2005 to 2007. Arrangements of passive acoustic receivers allowed analysis of movement at several spatial scales, with sex and size examined as possible factors influencing the pattern and timing of these movements. Notorynchus cepedianus exhibited a distinctly seasonal pattern of estuary use over three consecutive years, entering Willapa Bay in the spring, residing therein for extended periods of time during the summer and dispersing into nearshore coastal habitats and over the continental shelf during the autumn. Notorynchus cepedianus within Willapa Bay showed spatio-temporal patterns of segregation by size and sex, with males and small females using peripheral southern estuary channels early in the season before joining large females, who remained concentrated in central estuary channels for the entire season. Individuals displayed a high degree of fidelity not only to Willapa Bay (63% were documented returning over three consecutive seasons), but also to specific areas within the estuary, showing consistent patterns of site use from year to year. Cross-estuary movement was common during the summer, with most fish also moving into an adjacent estuarine embayment for some extent of time. Most winter and autumn coastal detections of N. cepedianus were made over the continental shelf near Oregon and Washington, U.S.A., but there were also examples of individuals moving into nearshore coastal habitats further south into California, suggesting the feasibility of broad-scale coastal movements to known birthing and nursery grounds for the species. These findings contribute to a better understanding of N. cepedianus movement ecology, which can be used to improve the holistic management of this highly mobile apex predator in regional ecosystems.

Relatedness and polyandry of sixgill sharks, Hexanchus griseus, in an urban estuary

The bluntnose sixgill shark (Hexanchus griseus) is a widely distributed species found in tropical and temperate waters of every ocean, yet we know relatively little about their basic biology including their life history and population structure. From 2003–2007, we collected over 300 biopsy samples from sixgills during research operations in Puget Sound, WA, USA. Genotypic data using ten polymorphic microsatellites were used to describe sixgill genetic diversity, relatedness and mating pattern. Diversity within sixgills was found to be moderate with an average observed heterozygosity of 0.45, an average expected heterozygosity of 0.61, an average of 12 alleles per locus, and an average allelic richness of eight within microsatellite loci. Our data suggests all of the sampled individuals come from one intermixing population, and we found no historical evidence of significant population bottlenecks. Many of the sharks were sampled using longline techniques with several sharks captured at the same time and place. Similarly, multiple sharks were sampled on several occasions during research events at the Seattle Aquarium. The proportion of individuals that were full- or half-siblings was high among sharks sampled at the same time and place (range 0.65–0.87). Analysis of the genetic relationship between one large female washed ashore and 71 of her near-term pups suggested a polyandrous mating system with as many as nine males contributing to her offspring. This study is the first to investigate genetic diversity, relatedness and paternity within sixgill sharks and sheds light on important conservation implications for this little known shark population.

Catch Rates and Biological Characteristics of Bluntnose Sixgill Sharks in Puget Sound

Abstract The bluntnose sixgill shark Hexanchus griseus is a wide-ranging marine predator and the largest predatory shark in Puget Sound. Biological characteristics of the Puget Sound bluntnose sixgill shark population remain largely undocumented, despite a recent escalation in recreational angling for the species. Standardized longline sampling, supplemented with other opportunistic collections, was used to collect size, sex ratio, and relative catch rate data at three locations during 2006–2008. Fishing trials were also used to examine the effect of soak time, fishing depth, and time of day on catch rates. Captured bluntnose sixgill sharks were exclusively subadults (175–315 cm total length) found in approximately equal sex ratios in all seasons. Catch rates were highest in Elliott Bay, the urbanized port of Seattle, Washington, and were not affected by sampling season. Catch information derived from hook timers implies that the sharks locate and encounter baited hooks relatively rapidly (<2 h); diel fis...

The legacy of a crowded ocean: indicators, status, and trends of anthropogenic pressures in the California Current ecosystem

As human population size and demand for seafood and other marine resources increase, understanding the influence of human activities in the ocean and on land becomes increasingly critical to the management and conservation of marine resources. In order to account for human influence on marine ecosystems while making management decisions, linkages between various anthropogenic pressures and ecosystem components need to be determined. Those linkages cannot be drawn until it is known how different pressures have been changing over time. This paper identifies indicators and develops time series for 22 anthropogenic pressures acting on the USAs portion of the California Current ecosystem. Time series suggest that seven pressures have decreased and two have increased over the short term, while five pressures were above and two pressures were below long-term means. Cumulative indices of anthropogenic pressures suggest a slight decrease in pressures in the 2000s compared to the preceding few decades. Dynamic factor analysis revealed four common trends that sufficiently explained the temporal variation found among all anthropogenic pressures. This reduced set of time series will be a useful tool to determine whether links exist between individual or multiple pressures and various ecosystem components.

An ecosystem‐based approach to marine risk assessment

Abstract Risk assessments quantify the probability of undesirable events along with their consequences. They are used to prioritize management interventions and assess tradeoffs, serving as an essential component of ecosystem‐based management (). A central objective of most risk assessments for conservation and management is to characterize uncertainty and impacts associated with one or more pressures of interest. Risk assessments have been used in marine resource management to help evaluate the risk of environmental, ecological, and anthropogenic pressures on species or habitats including for data‐poor fisheries management (e.g., toxicity, probability of extinction, habitat alteration impacts). Traditionally, marine risk assessments focused on singular pressure‐response relationships, but recent advancements have included use of risk assessments in an context, providing a method for evaluating the cumulative impacts of multiple pressures on multiple ecosystem components. Here, we describe a conceptual framework for ecosystem risk assessment (), highlighting its role in operationalizing , with specific attention to ocean management considerations. This framework builds on the ecotoxicological and conservation literature on risk assessment and includes recent advances that focus on risks posed by fishing to marine ecosystems. We review how examples of s from the United States fit into this framework, explore the variety of analytical approaches that have been used to conduct s, and assess the challenges and data gaps that remain. This review discusses future prospects for s as decision‐support tools, their expanded role in integrated ecosystem assessments, and the development of next‐generation risk assessments for coupled natural–human systems.

Suitability of Insulin-Like Growth Factor 1 (IGF1) as a Measure of Relative Growth Rates in Lingcod

Abstract The effectiveness of spatial management strategies is typically evaluated through traditional biological measurements of size, density, biomass, and the diversity of species inside and outside management boundaries. However, there have been relatively few attempts to evaluate the processes underlying these biological patterns. In this study, we take the first step toward developing a relative index of body growth for lingcod Ophiodon elongatus using plasma insulin-like growth factor 1 (IGF1) with the ultimate goal of measuring spatial differences in relative growth rates. Insulin-like growth factor 1 is one of the principal hormones that stimulates growth at the cellular level in all vertebrates and shows significant relationships with body growth in many fishes. In the laboratory, we found that the level of IGF1 was related to the instantaneous growth of juvenile lingcod. In the field, we measured size, condition, and plasma IGF1 level in 149 lingcod from eight locations inside and outside marine protected areas in the San Juan Islands, Washington. The IGF1 levels in wild lingcod were highly variable from site to site for both genders, and we were able to detect differences in IGF1 across space in males. Multivariate analyses showed that the spatial patterns of IGF1 differed from those of traditional biological measurements. More work is needed to validate the relationship between IGF1 and growth in larger individuals, but our research shows the potential for IGF1 to be used as an ecological indicator.

Comparing Apples to Oranges: Common Trends and Thresholds in Anthropogenic and Environmental Pressures across Multiple Marine Ecosystems

Ecosystem-based management (EBM) in marine ecosystems considers impacts caused by complex interactions between environmental and anthropogenic pressures (i.e. oceanographic, climatic, socio-economic) and marine communities. EBM depends, in part, on ecological indicators that facilitate understanding of inherent properties and the dynamics of pressures within marine communities. Thresholds of ecological indicators delineate ecosystem status because they represent points at which a small increase in one or many pressure variables results in an abrupt change of ecosystem responses. The difficulty in developing appropriate thresholds and reference points for EBM lies in the multidimensionality of both the ecosystem responses and the pressures impacting the ecosystem. Here, we develop thresholds using gradient forest for a suite of ecological indicators in response to multiple pressures that convey ecosystem status for large marine ecosystems from the US Pacific, Atlantic, sub-Arctic, and Gulf of Mexico. We detected these thresholds of ecological indicators based on multiple pressures. Commercial fisheries landings above approximately 2-4.5 t km-2 and fisheries exploitation above 20-40% of the total estimated biomass (of invertebrates and fish) of the ecosystem resulted in a change in the direction of ecosystem structure and functioning in the ecosystems examined. Our comparative findings reveal common trends in ecosystem thresholds along pressure gradients and also indicate that thresholds of ecological indicators are useful tools for comparing the impacts of environmental and anthropogenic pressures across multiple ecosystems. These critical points can be used to inform the development of EBM decision criteria.

Cooperative research sheds light on population structure and listing status of threatened and endangered rockfish species

Population genetics has increasingly become an important tool for determining appropriate taxonomic units for managing species of conservation interest. Yelloweye rockfish (Sebastes ruberrimus), canary rockfish (S. pinniger) and bocaccio (S. paucispinis) in the inland waterways of Puget Sound (PS), WA, USA were listed under the U.S. Endangered Species Act (ESA) in 2010. These listings relied heavily on evidence from other species that these populations were ‘discrete’ taxonomic units because little information was available for these species in PS. To fill this data gap, we collaborated with recreational fishing communities in PS to collect tissue samples and used population genetics analyses to determine whether samples from PS were genetically differentiated from samples collected from the outer coasts of the U.S. and Canada. Multiple analyses using restriction-site associated DNA sequencing data showed that yelloweye rockfish in PS and British Columbia, Canada were genetically different from coastal populations, while canary rockfish showed no genetic differentiation. These results support hypotheses that the genetic connectivity of rockfish populations is based on interactions between life-history characteristics and oceanographic conditions. These data also support the ESA designation status and the expansion of protected geographical boundaries for yelloweye rockfish but also suggest canary rockfish in PS are not a ‘discrete’ population and may not meet the first criterion of the ESA, as initially assumed. Collaboration among agencies and fishing communities, and cost-efficient genetic analyses provided a framework for collecting and analyzing data essential to the conservation and management of threatened and endangered species.