The 2011 climate regime shift: seabed taxon monitoring identifies regimes

Monitoring of biodiversity may sometimes reflect human impacts on ecosystems, but analysis of biodiversity needs to account for naturally occurring trends as well. Biodiversity may provide more accurate definition of climate regime shifts than do physical oceanographic data, Using search programs for a long-term SCUBA taxonomic database (3865 dives) for Strait of Georgia seabed sites, 1,077 taxa were screened to select 171 rare or highly abundant taxa and to present the data according to climate regime categories. Ocean Niño Index climate regime shifts are defined here as the year of the end of the first La Niña closely paired with an El Niño by separation, where anomalies for both El Niño and La Niña exceed 1.0 on the ONI scale. For both rare and abundant taxa, patterns of increased or decreased abundance frequently correspond to years defining climate regimes. Cascading effects of climate regime shifts may occur via changes in community composition. The sea star wasting disease (SSWD) syndrome eliminated predators of urchins so that urchins have decreased abundance of a kelp species that is nursery habitat for spot prawns. We conclude that 2011 was a climate regime shift. This 2011 regime shift coincided with disappearance of 11 seabed species from our Strait of Georgia dataset, none of them at their southern range extreme. Both increases and decreases in species abundance tend to coincide with climate regime shifts that have occurred regularly as a fundamental aspect of weather and climate on earth

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

Cloud Sponge, Aphrocallistes vastus (Porifera: Hexactinellida), fragment healing and reattachment

In May 2012, fragments of Cloud Sponge, Aphrocallistes vastus, that had been cut by fishing line were deposited in an array of boulders on the seabed near the parent sponge on the southwest shore of Hutt Island in Howe Sound near Vancouver, British Columbia. Open breaks in the transplanted fragments and parent sponge healed within 12 months. The fragments reattached to rock within 24 months. Previous observers of similar events reported no healing and death of damaged sponges. However, previous observations occurred during warm El Niño periods, which may be associated with higher stress leading to unsuccessful healing. In contrast, my current observations took place in cooler La Niña conditions, which may have promoted greater resilience and better healing

Glass sponge bioherms in Howe Sound: mapping, citizen science and impacts of climate and fishing

There are three species of glass sponges (Class Hexactinellida) that are capable of forming reefs (bioherms). Historically, glass sponge bioherms have been discovered along the NW Pacific Coast of Canada through multi-beam sonar surveys. However, twelve bioherms have been discovered in Howe Sound through a novel and inexpensive drop camera system that were missed in previous sonar explorations of the area due to incompatibility of the sonar resolution with the steep, complex bathymetry of the fjord. Of these bioherms, ten are shallower than 50 meters and accessible by SCUBA for hands-on research, six of them amenable to diving on compressed air (30-40m). These bioherms provide a unique opportunity for citizen science-driven/-partnered research. Various citizen science partnerships and projects are currently underway, such as one designed to observe long-term benthic temperatures within bioherms. This project will endeavour to further our understanding of the effects of El Niño Southern Oscillation (ENSO) events on glass sponge growth and decay cycles. Cloud sponge mortality has been associated with the 2009/2010 and 2015/2016 El Niños. Another project has proven ability for tissue repair during La Niña events. The principal citizen science initiative of Howe Sound bioherm exploration also provided direct evidence of damage by prawn trapping. These newly discovered sites in Howe Sound are providing unparalleled opportunities for leading-edge glass sponge and bioherm research that can involve the community as a partner. Citizen science participation increases environmental awareness and understanding which will increase public stewardship to this globally unique ecosystem

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

Box plots comparing times to attack by kelp greenling and copper rockfish in the absence of the model predator (‘no predator’ treatment).

<p>Because mesopredator densities varied by species and reef, times were multiplied by local density as a weighting factor.</p

Interactions between mesopredators and tethered prey adjacent to the model predator (fibreglass replica of an adult lingcod seen in the background).

<p>In panel A vertical arrows point to <i>Pandalus</i> shrimps tethered to the chain behind (only antennae are visible for peripheral shrimps). The left-pointing arrow indicates a male kelp greenling closely inspecting prey while swimming rapidly through the vicinity of the model predator. The right-pointing arrow indicates a copper rockfish inspecting prey while slowly swimming at a greater distance. Panel B shows an attack by a female kelp greenling, the species least responsive to the model predator, during the same trial.</p

Box plots comparing the probabilities that different species of mesopredators will (A) inspect or (B) attack tethered prey during experimental treatments.

<p>Numbers above boxes in panel A indicate sample sizes (i.e., number of reefs in which the treatment was replicated and the particular species was present); these same numbers apply to panel B. Boxes enclose the median (centerline) and 25th and 75^th percentiles (boundaries of the box); line caps indicate 10th and 90th percentiles.</p

Map of the study area. Black circles represent study reefs (labelled in italics).

<p>Map of the study area. Black circles represent study reefs (labelled in italics).</p

Predatory fishes affect trophic cascades and apparent competition in temperate reefs

We provide evidence for a trophic cascade involving apex predators and mesopredators of marine temperate reefs, lingcod and rockfish, respectively. We measured spatio-temporal variation in the relative abundance of lingcod, subadult rockfish and two shrimp groups eaten by rockfish (Pandalus sp. and three smaller-bodied genera aggregated). Lingcod had an indirect positive effect on shrimps, as mediated by the direct negative effects of lingcod on rockfish and of rockfish on shrimps. These top-down effects on shrimps, however, were stronger for Pandalus than for small-bodied shrimps. Further, abundances of Pandalus and small-bodied shrimps were negatively correlated and the latter had a stronger positive effect on rockfish, suggesting that rockfish mediated asymmetrical apparent competition between shrimps. Our results indicate mechanisms by which predatory fishes may influence the structure of marine communities