Search The Database

Short term behavioral responses of Chilean dolphins (Cephalorhynchus eutropia) to acoustic alarms, or pingers, were tested using exposure-control experiments (pinger on/off treatments). Field trials were conducted in the south-eastern Chiloe Archipelago  between February and April of 2013. BananaBP154 pingers (FishTek Marine) were used for the tests. Static passive acoustic monitoring (PAM) techniques were used at two sites (Bahia Yaldad and Canal San Pedro) and land based observations, which included theodolite tracking, were also conducted at Bahia Yaldad. Static PAM techniques and C-PODs were used to determine the effects of a single pinger on echolocation rates and movement patterns. Fifty seven groups of Chilean dolphins were tracked with the theolodite, with 45 groups providing good resolution movement data within the vicinity of the pinger. Visual data are currently being analysed to determine effects of a single acoustic alarm on movement patterns, grouping behavior and spatial area use of the dolphins. Acoustic encounter rates of Chilean dolphins at the six C-PODs are currently being analysed. Preliminary analysis suggest pingers are unlikely to have caused substantial behavioral changes in Chilean dolphins.

Fisheries observer data from six gear types operating in the US Northeast and mid-Atlantic were analysed for seabird interactions. Between 1996 and 2014 an estimated 48,821 seabirds interacted with commercial fishing gear. This resulted in an estimated average interaction rate of 2,570 seabirds per year. The majority of interactions occurred in gillnet fisheries and involved shearwaters/fulmars. A comparison with previous work in the region was also conducted. This comparison highlighted the need for consistency in data preparation to relative trends in seabird bycatch in the region can be compared. Additional analysis should provide context for interaction estimates to allow for population-level impacts to be inferred.

Bycatch interactions with deep-sea elasmobranchs are increasingly common and can lead to dramatic declines in abundance over short time scales. Sharks hooked in the deep sea could face a higher likelihood of severe physiological disturbance, at-vessel mortality, and post-release mortality (PRM) than their shallower counterparts. Unfortunately, robust PRM rates have not yet been estimated for longline-caught deep-sea sharks, and as such are not currently incorporated into total fishery mortality estimates or bycatch assessments, limiting the effectiveness of current conservation or management initiatives. We empirically estimated PRM for 2 focal taxa of deep-sea shark, the Cuban dogfish Squalus cubensis and the gulper shark Centrophorus sp., using post-release enclosures deployed at-depth. We calculated 24 h PRM rates of 49.7 ± 8.5% (mean ± SE) for S. cubensis and 83 ± 16% for Centrophorus sp. and identified blood lactate, total length, glucose, and vitality scores as predictors of PRM in S. cubensis. We also observed all 24 h PRM within 11 h post-capture and demonstrated the effects of recovery depth and at-vessel blood chemistry metrics on post-release behavior. Our results suggest that PRM rates of deep-sea sharks are high and highlight the need for filling in this gap in fishery mortality estimates for other common discards in the future.

Estimates of post-release mortality (PRM) rates for discarded bycatch are largely unknown across marine fisheries and represent a substantial source of uncertainty when estimating total fishery mortality. One way to predict PRM is through the use of reflex action mortality predictors (RAMP), whereby the presence or absence of target reflexes and known post-release fate are used to create a delayed mortality model. We employed reflex impairment assessments in concert with post-capture caging and video monitoring to predict 5-d PRM rates for the deep-sea giant isopod Bathynomus giganteus , a common bycatch species in numerous deepwater fisheries worldwide, and also considered the factors contributing to mortality. Mortality rates 5 d post-capture ranged from 50 to 100% and both RAMP scores and time at the surface were significant predictors of mortality, although our conclusions regarding the effect of surface time are limited. In-cage video documented little movement within the 24-h monitoring period following capture, and it appeared that surviving individuals often fed within the holding period after cage deployment. Our results suggest that PRM in B. giganteus is common and that this unaccounted source of mortality should be quantified for other deep-sea crustaceans captured as bycatch.

Light-emitting diodes (LEDs) were mounted on the lower part of a Nordmore grid to determine if they would encourage fish to move up towards the escape outlet prior to contacting the grid. Trials were conducted to assess the size selective properties of a 19 mm bar spaced Nordmore grid with and without LEDs. The target in the fishery is deep water shrimp (Pandalus borealis). Small fish are bycatch, with 51-100% passing through the Nordmore grid. The use of LEDs in addition to the Nordmore grid did not significantly affect the escape probability or the size selectivity of any species.

The potential benefits of permanent magnets on ocean fish traps targeting snapper (Pagrus auratus) and their abiliy to reduce elasmobranch bycatch. The study deployed over 1000 traps in a fishery-dependent survey in New South Whales, Australia. The incorporation of magnets into fish traps significantly reduced incidences of elasmobranch bycatch by more than a thrid. At the same time, the target species catch rate was significantly increased. Magnets can therefore be used as an effective bycatch reduction device to reduce interactions with elasmobranchs.

Fishery data collected from the Reunion Island and Sechelles pelagic longline fisheries (targeting swordfish and tuna) between 2004 and 2015 was used to propose depredation indicators and to assess depredation levels in these fisheries. The interaction rate (depredation) was significantly higher for sharks compared to toothed whales in both fisheries. However, there was a higher depredation per unit effort from toothed whales compared to sharks indicating the impact was more significant. The gross depredation rate in the Seychelles fishery was 18.3%. A slight increase in the gross depredation rate was seen over time in the Reunion Islands fishery (4.1% 2007-2010 and 4.4% in 2011-2015). These indicators were used to estimate the economic loss to these fisheries from depredation events. For the Reunion Island fishery the economic loss was 0.09 EUR/hook and 0.86 EUR/hook for the Seychelles. The results suggest a southward decreasing tooth whale and shark depredation gradient. The depredation levels in the Seychelles are some of the highest in the world and may suggest a 'hot spot' of interactions between toothed whales and pelagic longlines.

Experiments on the use of sea bird mitigation methods were conducted aboard Uruguayan pelagic longliners between 2010 and 2012. Experiments looked at the difference between setting bait at the sea surface and setting baits underwater. The researchers recorded the abundance of sea birds following the vessel and incidences of attacks on bait and mortality. When the bait was set underwater, there was a marked reduction in the number of seabirds following the vessel and attacks on bait. Mortality levels of birds caught on bait set 4 m below the surface were 87% lower than mortality levels for birds when bait was set at the surface. There were no bird mortalities when bait was set 10 m below the surface. The mortality level of birds when bait was set at the surface was 11.6 birds/1000 hooks.  No differences in catch rates of target species (tuna) were observed when bait was set at the surface or below the surface.

This research examined the spatial and temporal characteristics of pilot whale habitat use and longline fishing effort. The information was used to assess the potential for a spatial management approach to mitigate pilot whale bycatch. The Area Under the Curve and Williamson's Spatial Overlap Index were both used to assess patterns of overlap and bycatch by applying them to telemetry data from short-finned pilot whales, longline fishery effort and Pelagic Observer Program (POP) data (2014-2015). Based on this analysis, important variables influencing pilot whale-longline overlap and POP bycatch rates include: proximity to the 1000 m isobath, season, and sea surface temperature. Pilot whales had the highest density inshore of the 1000 m isobath. Longline effort along this isobath varies seasonally. Seasonal patterns in pilot whale-longline overlap relative to the 1000 m isobath were significantly correlated with POP bycatch rates, with the highest bycatch rates occurring in the fall and winter months. Based on these results, the authors suggest that a spatial management approach for this unsustainable bycatch warrants further investigation, and provide suggestions for changing how fisheries observers might be deployed to provide data helpful for evaluating a spatio-temporal management strategy for reducing pilot whale bycatch in eastern US pelagic longline fisheries. 

The annual counts of large whale entanglements (including serious injury and mortalities) were analyzed and used to assess the effectiveness of the Atlantic Large Whale Take Reduction Plan. Fishing gear entanglements related to the annual number of mortality events averaged 2.5 for right whales (Eubalaena glacialis), 5.6 for humpback (Megaptera novaeangliae), 0.6 for fin whales (Balaenoptera physalus) and 2.4 for minke whales (B. acutorostrata). Annual entanglement rates increased during the study period (1999-2009), increased rates of entanglement-related mortality were equivocal. There were no significant changes in waiting time in response to any management measures implemented to reduce large whale mortalities between 1999 and 2009. This implies the measures were generally ineffective.