Transdisciplinary research that crosses disciplinary boundaries and includes stakeholder collaboration is increasingly being used to address pressing and complex socio-ecological challenges in the Anthropocene. In fisheries, we see transdisciplinary approaches being employed to address a range of challenges, including bycatch where fine-scale data are collected by fishers to help advance spatial approaches in which fishing effort is shifted away from bycatch hotspots. However, the spatio-temporal overlap of morphologically undistinguishable fish stocks, some of which are depleted, is a major concern for some fisheries, including the Pacific Northwest troll Chinook salmon (Oncorhynchus tshawytscha) fishery. In this study, we develop and evaluate a transdisciplinary approach to avoid bycatch in the commercial Chinook salmon troll fishery off northern and central Oregon. Based on a unique genetic dataset collected by fishers, fine-scale patterns of stock distribution and spatial stock overlap were assessed. Two hotspots of weak Klamath stock in the study region were identified and related to bathymetry. Results were then fed into a simple bioeconomic model to evaluate costs and benefits of reallocating effort under two scenarios of allowable catch of a weak stock (Klamath). The scenarios demonstrate that effort reallocation could lead to a reduction in Klamath catch as well as to increases in net profit, but outcomes depend on the distance from the fleets' home port to the new fishing area. The output of the model at its current stage should be regarded strategically, providing a qualitative understanding of the types of best fleet strategies. Despite some challenges in transdisciplinarity discussed in this study and the present limitations to incorporate fine-scale changes of Chinook salmon stock distributions in management regulations, we contend that this approach to research has the potential to lead to improved management outcomes.
Rebuilding of some U.S. West Coast rockfish (Sebastes spp.) stocks relies heavily on mandatory fishery discard, however the long-term condition of discarded fish experiencing capture-related barotrauma is unknown. We conducted two studies designed to evaluate delayed mortality, physical condition, and behavioral competency of yelloweye rockfish, Sebastes ruberrimus, experiencing barotrauma during capture followed by recompression (assisted return to depth of capture). First, we used sea-cage and laboratory holding to evaluate fish condition at 2, 15, and 30 days post-capture from 140 to 150 m depth. All external barotrauma signs resolved following 2 days of recompression, but fish that survived (10/12) had compromised buoyancy regulation, swim bladder injuries, and coelomic and visceral hemorrhages at both 15 and 30 days post-capture. For the second study, we used a video-equipped sea-cage to observe fish behavior for one hour following capture and return to the sea floor. Trials were conducted with 24 fish captured from 54 to 199 m water depth. All fish survived, but 50% of fish from the deepest depth ranges showed impairment in their ability to vertically orient (P < 0.01). Most (75%) deep-captured fish did not exhibit “vision-dependent” behavior (P < 0.001) and appeared unable to visually discern the difference between an opaque barrier and unobstructed or transparent components of the cage. These studies indicate physical injuries and behavioral impairment may compromise yelloweye rockfish in the hours and weeks following discard, even with recompression. Our results reiterate the importance of avoiding fishing contact with species under stock rebuilding plans, especially in deep water, and that spatially-managed rockfish conservation areas remain closed to fishing.
Antarctic krill (Euphausia superba) is an abundant fishery resource, the harvest levels of which are expected to increase. However, many of the length classes of krill can escape through commonly used commercial trawl mesh sizes. A vital component of the overall management of a fishery is to estimate the total fishing mortality and quantify the mortality rate of individuals that escape from fishing gear. The methods for determining fishing mortality in krill are still poorly developed. We used a covered codend sampling technique followed by onboard observations made in holding tanks to monitor mortality rates of escaped krill. Haul duration, hydrological conditions, maximum fishing depth and catch composition all had no significant effect on mortality of krill escaping 16 mm mesh size nets, nor was any further mortality associated with the holding tank conditions. A non- parametric Kaplan-Meier analysis was used to model the relationship between mortality rates of escapees and time. There was a weak tendency, though not significant, for smaller individuals to suffer higher mortality than larger individuals. The mortality of krill escaping the trawl nets in our study was 4.4 ± 4.4%, suggesting that krill are fairly tolerant of the capture-and-escape process in trawls.
The diamondback terrapin (Malaclemys terrapin) is endemic to marshes, coves, and tidal creeks on the Atlantic and Gulf coasts of the United States. Currently, the terrapin is listed as a species of special concern in several states where one of the prominent threats to populations is the drowning of terrapins in commercial crab pots. Bycatch reduction devices (BRDs) that narrow the funnel opening on crab pots exclude terrapins, but BRDs face opposition from the fishing industry due to fears that they will decrease target species catch. The primary goals of this research were to examine the efficacy of two sizes of BRDs in excluding terrapins from crab pots and to assess the impact of BRDs on blue crab catch. Crab pots were deployed in paired and triplicate designs at estuarine sites along the central and southern coast of North Carolina in the summers of 2012 and 2013. A total of 4039 legal sized blue crabs and 14 terrapins were captured over the course of the study. Bycatch reduction devices did not have a statistically significant effect on catch rates or carapace width of legal-sized blue crabs. Thirteen of the 14 captured terrapins were in control pots, and one male terrapin was captured in a pot equipped with a large size BRD. An integrated approach that combines data on the spatial ecology and demography of terrapins with information on the most appropriate BRD dimensions for terrapin exclusion is most likely to succeed in addressing the issue of terrapin bycatch.
Underwater video recordings in the mouth of a squid trawl were used to evaluate the effectiveness of a trawl configured with drop-chain groundgear to catch longfin inshore squid (Doryteuthis pealeii) and reduce bycatch of finfish in the Nantucket Sound squid fishery off Cape Cod, Massachusetts, USA. Entrance through the trawl mouth or escape underneath the fishing line and between drop chains was quantified for targeted squid, and two major bycatch species, summer flounder (Paralichthys dentatus) and skates (family Rajidae). Additionally, contact and impingement between animals and groundgear were also quantified. Fish and squid swimming behaviours, positions, orientations, and time in the trawl mouth were quantified and related to capture or escape at the trawl mouth. Squid entered the trawl singly and in schools, and no squid were observed escaping under the fishing line. Most squid entered the trawl in the upper portion of the trawl mouth; mantle orientated away from the trawl and swimming in the same direction, and were gradually overtaken, not actively attempting to escape. Summer flounder and skates were observed to remain on or near the seabed, orientated, and swimming in the same direction as the approaching trawl. The majority (60.5%) of summer flounder entered the trawl above the fishing line. Summer flounder that changed their orientation and turned 180° were significantly more likely to enter the trawl (p < 0.05). Most skates (89.7%) avoided trawl entrance and escaped under the fishing line. Neither squid nor summer flounder were observed to make contact or become impinged to the groundgear; however, 35.4% of skates had substantial contact with groundgear, with 12.3% becoming impinged. Video analysis results showed that the drop-chain trawl is effective at retaining targeted squid while allowing skates to escape. However, it is ineffective at avoiding the capture of summer flounder.
A dedicated observer programme was carried out in gillnet and entangling net fisheries off the west and southwest coasts of Ireland to monitor interactions with seals. No seals were observed as bycatch in gillnet fisheries suggesting the risk of bycatch in observed gillnet fisheries is low. Grey seals (Halichoerus grypus) and to a lesser extent harbour seals (Phoca vitulina) were observed as bycatch principally in large mesh tangle nets targeting crawfish (Palinurus elephas). Observed bycatch levels, proximity of grey seal colonies to crawfish fisheries and similar habitat preferences suggest that the risk of seal bycatch in tangle net fisheries for crawfish on the west and southwest coasts of Ireland is high. Factors affecting bycatch in tangle nets were modeled to investigate potential bycatch mitigation measures. Crawfish and monkfish (Lophius spp.) catches, depth of gear deployment and larger mesh size were significantly positively correlated with seal bycatch. Development of mitigation measures such as improved net visibility, use of smaller mesh size and reintroduction of pots has major potential to reduce seal bycatch in the observed tangle net fishery. Growing seal populations in regions where tangle netting for crawfish is most prevalent could be related to factors such as benefits accrued from depredation and possible immigration from adjacent populations in the UK. More explicit conservation objectives will likely be needed to provide an impetus for development of proposed mitigation measures and bycatch reductions in Ireland. Results of this study also have broader ramifications for management of pinniped bycatch in large mesh gillnet and entangling net fisheries, which are widespread but poorly studied in European Community waters.
The deepwater chondrichthyan fauna of the Great Barrier Reef is poorly known and life history information is required to enable their effective management as they are inherently vulnerable to exploitation. The chondrichthyan bycatch from the deepwater eastern king prawn fishery at the Swain Reefs in the southern Great Barrier Reef was examined to determine the species present and provide information on their life histories. In all, 1533 individuals were collected from 11 deepwater chondrichthyan species, with the Argus skate Dipturus polyommata, piked spurdog Squalus megalops and pale spotted catshark Asymbolus pallidus the most commonly caught. All but one species is endemic to Australia with five species restricted to waters offshore from Queensland. The extent of life history information available for each species varied but the life history traits across all species were characteristic of deep water chondrichthyans with relatively large length at maturity, small litters and low ovarian fecundity; all indicative of low biological productivity. However, variability among these traits and spatial and bathymetric distributions of the species suggests differing degrees of resilience to fishing pressure. To ensure the sustainability of these bycatch species, monitoring of their catches in the deepwater eastern king prawn fishery is recommended.
Capture in global pelagic longline fisheries threatens the viability of some seabird populations. The Hawaii longline tuna fishery annually catches hundreds of seabirds, primarily Laysan (Phoebastria immutabilis) and black-footed (P. nigripes) albatrosses. Since seabird regulations were introduced in 2001, the seabird catch rate has declined 74%. However, over the past decade, seabird catch levels significantly increased due to significant increasing trends in both effort and nominal seabird catch rates. We modelled observer data using a spatio-temporal generalized additive mixed model with zero-inflated Poisson likelihood to determine the significance of the effect of various risk factors on the seabird catch rate. The seabird catch rate significantly increased as annual mean multivariate ENSO index values increased, suggesting that decreasing ocean productivity observed in recent years in the central north Pacific may have contributed to the increasing trend in nominal seabird catch rate. A significant increasing trend in number of albatrosses attending vessels, possibly linked to declining regional ocean productivity and increasing absolute abundance of black-footed albatrosses, may also have contributed to the increasing nominal seabird catch rate. Largest opportunities for reductions are through augmented efficacy of seabird bycatch mitigation north of 23° N where mitigation methods are required and during setting instead of during hauling. Both side vs. stern setting, and blue-dyed vs. untreated bait significantly reduced the seabird catch rate. Of two options for meeting regulatory requirements, side setting had a significantly lower seabird catch rate than blue-dyed bait. There was significant spatio-temporal and seasonal variation in the risk of seabird capture with highest catch rates in April and May and to the northwest of the main Hawaiian Islands.
Geographically weighted regression (GWR) is a relatively new technique to explore spatially-varying relationships between biological and environmental processes. It allows parameters to vary over space and assumes data to follow a normal distribution. We extend GWR to a geographically weighted generalized linear model (GW-GLM) by incorporating statistical distributions other than the normal distribution (i.e., the binomial distribution). We demonstrate the application of GW-GLM with an empirical example, U.S. Atlantic pelagic longline seabird bycatch. Due to the high percentage of zero observations in the seabird bycatch data, we analyzed the positive catch rates (number of seabirds caught per 1000 hooks) and the probability of catching a seabird separately. Parameter estimates exhibited considerable spatial variation, especially for target catch rate when analyzing the positive catch data, and for intercept, water depth and water temperature when estimating the probability of catching seabirds. We compared model performance of GW-GLM with a global generalized linear model, a mixed effect model with a random areal effect, and a spatial expansion model that is an early technique to model spatially-varying ecological relationships by modeling each of the parameters as a function of location. The GW-GLM performed best. Simulations with hypothetical datasets having different percentages of zeros showed that, regardless of the zero percentage in the data, GW-GLM performed best on average. Applying a range of bandwidth indicated that the GW-GLM was more robust to an overestimated bandwidth than an underestimated bandwidth.
Since 2011, NOAA’s National Marine Fisheries Service (NMFS) has published a series of National Bycatch Reports and Updates because estimating bycatch rates in fisheries in order to understand bycatch levels, as well as fishery interactions with protected species, is important to effective living marine resource management. These reports, along with other information sources, are expected to help improve NMFS’ ability to monitor bycatch trends and set fishery monitoring priorities, as well as serve as a useful data tool for NMFS and its management partners.
The First Edition of the National Bycatch Report (NMFS 2011) documented bycatch estimates, using observer data and self-reported logbook data, for all fisheries for which this information was available in 2005. NMFS completed Update 1 (NMFS 2013a) in late 2013 and published it online in early 2014. Update 1 included bycatch estimates based for the most part on 2010 data only.
This report, Update 2, includes three sets of bycatch estimates based on data from 2011, 2012, and 2013. The Second Edition of the National Bycatch Report, scheduled for publication in late 2017, will include bycatch estimates based on data from 2014 and 2015, as well as National and regional bycatch ratios; discussion of the Tier Classification System, Key Stocks, and Fisheries of Focus; and a detailed discussion of bycatch estimation improvement plans.