Rockfish size and age: The crossroads of spatial protection, central place fisheries and indigenous rights

AbstractIndigenous people harvest wild species for food and cultural practice, fundamentally linking biodiversity conservation and indigenous rights. Rockfishes (Sebastes spp.) are culturally significant to indigenous people (or First Nations) of coastal British Columbia (BC), Canada, who regulate their harvest under traditional governance structures. First Nations elders, however, have observed a decline in the body sizes and abundance of rockfishes, which coincides with increased exploitation by non-indigenous fishers. Rockfishes are vulnerable to overexploitation because fecundity and offspring quality increase with maternal size or age, yet fisheries truncate size and age structure. During 2006, 2007 and 2013–2015, we worked with the Wuikinuxv, Nuxalk, Heiltsuk and Kitasoo/Xai’Xais First Nations of BC’s Central Coast, examining rockfish population characteristics at 282 of their fishing sites. We used hook-and-line gear to collect fishery independent data, and sampled landings from First Nations subsistence fishers. Spatial fishery closures served as experimental treatments. We also applied central place foraging theory to predict declines in size, age and abundance with increasing distance from recreational fishing lodges and other ports. Analyses used linear mixed models and controlled for environmental variables. Our results suggest that spatial closures for commercial and recreational fishers led to greater size and abundance of some, but not all rockfishes, possibly due to interspecific differences in the extent to which closures contain suitable habitat, effects of non-compliance, or other factors. Notably, Yelloweye Rockfish (Sebastes ruberrimus), a species key to indigenous diets, were 21% larger inside than outside spatial closures. Possibly reflecting cumulative fishery exploitation, however, old-aged Yelloweye Rockfish were rare. Fishery impacts on size and relative abundance decreased at sites that required longer travel times and greater fuel costs for recreational fishers to exploit, but only for the longest-lived species (size responses) and for long-lived species analysed in aggregate (abundance responses). Measures for protecting indigenous access to rockfishes include evaluation of habitat suitability and compliance within spatial closures, improved understanding of recreational fishery impacts, and treating old-age and large size structures as explicit management objectives. Our study contributes to a global effort to integrate indigenous cultural values with biological conservation

Do shark declines create fear‐released systems?

We illustrate the theoretical plausibility that fishery removal of sharks can indirectly alter predation pressure on different fish species via the behavioural responses of mesoconsumers released from predator intimidation. Our dynamic state variable model of foraging decisions by harbour seals, a mesopredator, predicted indirect effects of the removal of Pacific sleeper sharks on two species consumed by seals, Pacific herring and walleye pollock, as mediated by seal behaviour. Herring, a fatty fish, form near-surface aggregations that often are ephemeral and widely dispersed. Pollock are found in the deeper strata preferred by sharks and have lower energy density than herring, but also are larger and their more continuous distribution potentially makes them the more predictable resource for seals. During simulations, predation risk from sharks produced an asymmetric trophic cascade mediated by the seal's underutilisation of deeper, riskier strata. Risk management by seals reduced mortality on pollock, which required riskier access in deep strata, while increasing mortality on herring, which could be accessed with less risk in shallow strata. This effect, however, attenuated if herring were scarcer and seal energy state was poor. During shark removal scenarios, seals shifted to deeper strata, increasing pollock consumption and substantially decreasing use of herring; the proportional change was greatest if seals were in good energy state. Prior studies have addressed how shark declines might affect community structure through density responses by species consumed by sharks; earlier models incorporating antipredator behaviour of the mesopredator (i.e. Ecosim/Ecospace) allow for activity reduction but not for the spatial shifts that altered the asymmetric trophic cascade in our simulations. Our results suggest that shark declines might have stronger ecological consequences than previously recognised if we account for spatial and diet shifts by mesoconsumers released from shark intimidation

Interspecific Variation in Life History Relates to Antipredator Decisions by Marine Mesopredators on Temperate Reefs

As upper-level predatory fishes become overfished, mesopredators rise to become the new ‘top’ predators of over-exploited marine communities. To gain insight into ensuing mechanisms that might alter indirect species interactions, we examined how behavioural responses to an upper-level predatory fish might differ between mesopredator species with different life histories. In rocky reefs of the northeast Pacific Ocean, adult lingcod (Ophiodon elongatus) are upper-level predators that use a sit-and-wait hunting mode. Reef mesopredators that are prey to adult lingcod include kelp greenling (Hexagrammos decagrammus), younger lingcod, copper rockfish (Sebastes caurinus) and quillback rockfish (S. maliger). Across these mesopredators species, longevity and age at maturity increases and, consequently, the annual proportion of lifetime reproductive output decreases in the order just listed. Therefore, we hypothesized that the level of risk taken to acquire resources would vary interspecifically in that same order. During field experiments we manipulated predation risk with a model adult lingcod and used fixed video cameras to quantify interactions between mesopredators and tethered prey (Pandalus shrimps). We predicted that the probabilities of inspecting and attacking tethered prey would rank from highest to lowest and the timing of these behaviours would rank from earliest to latest as follows: kelp greenling, lingcod, copper rockfish, and quillback rockfish. We also predicted that responses to the model lingcod, such as avoidance of interactions with tethered prey, would rank from weakest to strongest in the same order. Results were consistent with our predictions suggesting that, despite occupying similar trophic levels, longer-lived mesopredators with late maturity have stronger antipredator responses and therefore experience lower foraging rates in the presence of predators than mesopredators with faster life histories. The corollary is that the fishery removal of top predators, which relaxes predation risk, could potentially lead to stronger increases in foraging rates for mesopredators with slower life histories

Optimal risk-taking theory applied to marine conservation: Harbour seals in Prince William Sound

I sought theoretical insight on synergistic effects of resources and predators that are potentially relevant to the decline of harbour seals in Prince William Sound and to indirect effects of fisheries. Simulations predicted that compensatory foraging effort by seals will mitigate potential loss of energy reserves when resources decline, but only at the cost of higher predation rates, even if predator densities remain constant. A second study predicted net energy gain and predation risk per foraging dive, parameterising an analytical model with field data on seal behaviour, resource distributions, and use of depth by Pacific sleeper sharks and killer whales. Analyses suggested that risk of mortality from sharks and net energetic gain were greatest when seals foraged in deep strata, and empirical data showed individual variation in use of these strata. Plots of the individuals’ predicted energy gain against predicted predation risk fit best when relative danger from sharks was assumed to be much greater than that from killer whales. The first two studies combined suggest that, theoretically, overfishing of near-surface fatty fishes might increase shark predation rates on seals. A third model predicted an asymmetric trophic cascade in which indirect effects of sleeper sharks on resources were mediated by seal avoidance of riskier strata. Risk management by seals is predicted to reduce mortality on the dangerous resource (deep pollock) while increasing mortality on the safer resource (shallow herring), and the bycatch of sharks altered this dynamic. Although empirical data are lacking to test most predictions and various assumptions, the three models derive from first principles of behavioural ecology and provide a rigorous basis for predicting indirect effects of fisheries. Further, overfishing of sharks and of resources used by marine mammals are pressing global problems which cannot be addressed by empirical studies alone; indirect interactions between species are too complex to be elucidated without theoretical guidance and rapid exploitation often outpaces the acquisition of data relevant to conservation. Thus, theory presented here is important for assessing the potential damage wrought by different fishery scenarios, informing decisions that attempt to optimise exploitation and conservation, and guiding empirical research

Vigilance while feeding by female Dall’s sheep (Ovis dalli dalli Nelson, 1884): interactions among predation risk factors

I proposed and tested the Interactive Risk Factors Hypothesis (IRFH), in which predation risk factors have an interactive (multiplicative) rather than an independent (additive) effect on vigilance while feeding. Four predictions were tested on adult female Dall's sheep (Ovis dalli dalli) in the wild: 1) Vigilance increases with decreasing group size, but the magnitude of this response becomes smaller as (a) distance to cliffs decreases, and/or (b) distance to obstructive cover increases. 2) Vigilance increases with increasing distance to cliffs, but the magnitude of this response becomes smaller as (a) group size increases, and/or (b) distance to obstructive cover increases. 3) Vigilance increases with decreasing distance to obstructive cover, but the magnitude of this response becomes smaller as (a) group size increases, and/or (b) distance to cliffs decreases. 4) The magnitude of any of the above responses will be greater for mothers with neonates than for adult females within 2 months prior to the lambing season. Predictions 1a, 2a, and 4 were supported, implying that when risk is low due to other conditions, animals may increase vigilance very little or not at all in response to a particular factor that would otherwise have a strong effect. A priori analysis showed that distance to obstructive cover had no effect on vigilance (predictions 1 b, 2b and 3), which neither rejects nor supports the hypothesis. This result, however, was probably due to incomplete field measurements and a posteriori analysis suggested that distance to obstructive cover does have an interactive effect on vigilance. The IRFH is a general hypothesis that should be able to handle any other factors that affect risk, and is potentially applicable to any terrestrial prey. Testing for interactions among predation risk factors may provide a more realistic approach to understanding vigilance than merely assuming that such factors have independent effects.Land and Food Systems, Faculty ofGraduat

Behaviourally mediated biases in transect surveys: a predation risk sensitivity approach

Variation in the behaviour of individuals or species, particularly their propensity to avoid or approach human observers, their conveyances (e.g., cars), or their proxy devices (e.g., drones) has been recognized as a source of bias in transect counts. However, there has been little attempt to predict the likelihood or magnitude of such biases. Behavioural ecology provides a rich source of theory to develop a general framework for doing so. For example, if animals perceive observers as predators, then the extensive body of research on responses of prey to their predators may be applied to this issue. Here we survey the literature on flight initiation distance (the distance from a predator or disturbance stimulus at which prey flee) for a variety of taxa to suggest which characteristics of the animal, the observer, and the environment may create negatively biased counts. We also consider factors that might cause prey to approach observers, creating positive bias, and discuss when and why motivation for both approach and avoidance might occur simultaneously and how animals may resolve such trade-offs. Finally, we discuss the potential for predicting the extent of the behaviourally mediated biases that may be expected in transect counts and consider ways of dealing with them.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Home site fidelity in Black Rockfish, Sebastes melanops, reintroduced into a fjord environment

Between December 2004 and January 2007, we studied the movements of six Black Rockfish (Sebastes melanops) that had been fitted with acoustic transmitters and reintroduced into a fjord environment at the edge of Vancouver Harbour, British Columbia. The Black Rockfish were released in December 2004 and April 2005 at a reef characterized by complex rocky structures and steep slopes; bottom depths at the site dropped from 10 to 55 m within a horizontal distance of only 30 m. The reef, however, is small (approximately 4500 m2) and is surrounded by soft bottom habitats used infrequently by Black Rockfish. VEMCO VR2 receivers were deployed at the release site and at outlying reefs located 1 and 4 km away. Acoustic data suggest that one individual emigrated from the reef after 11 months of residency and a second individual disappeared abruptly after 6 weeks on the reef, possibly due to fishing mortality or emigration. The four remaining individuals appear to have confined their movements to the release site, using an area 6 to 10 times smaller than the home ranges reported for populations in low-gradient coastlines in California and Oregon

Rapid recovery of Dungeness crab within spatial fishery closures declared under indigenous law in British Columbia

Canada’s constitution grants indigenous people priority access to marine resources, yet indigenous, commercial and recreational fishers target the same species. Avoiding conflict between different users, therefore, requires evidence-based policies that manage fisheries for conservation while respecting indigenous rights. From 2006 to 2015, Canada’s Conservative government demoted the role of science in resource management, stifling research by federal agencies like Fisheries and Oceans Canada. To address ensuing data gaps, during 2014–2015 the Heiltsuk, Kitasoo/Xai’Xais, Nuxalk, and Wuikinuxv First Nations conducted coordinated research on Dungeness crab (Cancer magister), a culturally-significant resource. These indigenous groups are experiencing declining catch rates of Dungeness crab and postulate that commercial and recreational fisheries are primary causes of local declines. Accordingly, they applied indigenous laws and declared spatial fishery closures for commercial and recreational fishers at 10 sites (closed) while allowing exploitation by all users to continue at 10 other sites (open). Sampling occurred repeatedly over time and analyses compared temporal trends in population characteristics between closed and open sites. Results were consistent with the hypothesis that fisheries decrease the abundance and size of exploited species, but spatial protection can reverse these effects. The body size and catch-per-unit effort of legal-sized males increased over time at closed sites but declined at open sites. Importantly, fishery status did not affect temporal changes in the relative abundance of unfished classes of crab–sublegal males and females–which is logically consistent with the hypothesis. Our study demonstrates that indigenous governance can create spatial closures for conservation and research when Canada’s government fails to do so. Long-term solutions, however, require collaboration in research and management between federal and indigenous governments. Towards that end, Canada’s newly elected Liberal government has begun to restore federal science and to address indigenous rights, thereby enhancing the possibility of such collaboration

Cross-fertilizing Aquatic and Terrestrial Research to Understand Predator Risk Effects

Research that conceptually transcends boundaries between aquatic and terrestrial ecosystems has a long history of increasing insight into ecology and evolution. To stimulate further cross-fertilization between studies that focus on different ecosystems, we highlight several insights on risk effects—the costs of antipredator behavior—that have emerged in part because of combined advances in aquatic and terrestrial systems. Namely, risk effects (1) are not restricted to structured landscapes where antipredator behavior is easily measurable, (2) can be substantial even when prey experience very low predation rates, (3) are contingent on a three-way interaction between the hunting mode of the predator, escape tactic of the prey, and features of the landscape/physical environment, and (4) can interact with direct predation (consumption) and resource availability (through its effects on prey energy state) to control consumer population size. We conclude by highlighting the value of exploring differences between aquatic and terrestrial risk effects and offering a prospectus for future studies of antipredator behavior and its ecological importance in both eco-domains