MSc. Research
My MSc. research is centered on evaluating the suitability of entanglement mitigation methods for Atlantic Canada fixed-gear fisheries.
Geneviève holding a section of LBS rope (breaking strength of 1700lbs) that stretched and broke while inserted in a down rope while fishing.
Abstract
Entanglement in fishing gear is inhibiting the recovery of North Atlantic right whales (Eubalaena glacialis). Low breaking-strength (LBS) modifications have the potential to reduce severity of entanglements. Having a lower breaking strength of 1,700 lbf (771 kgf), compared to traditional ropes, they are designed to break under extreme pressure like a whale becoming entangled, reducing the severity and duration. The first part of this research aims to assess if the strength of LBS components is sufficient for the conditions of the Newfoundland and Labrador snow crab (Chionoecetes opilio) fishery by documenting tensions while hauling. Results showed that tension exceeded 771 kgf , when hauling traps, suggesting that LBS components are not suitable for this fishery. The second part of this thesis involved time-tension line cutters (TTLCs), a double-threshold (time and tension) entanglement mitigation device with which a tension of 771 kgf or over must be sustained for a set amount of time before a blade cuts the line, allowing the retrieval of gear without breakage within that time frame. Due to the use of hydraulic fluid within TTLCs and the known effect of temperature on its viscosity, a controlled laboratory experiment reflecting the conditions of Atlantic fisheries was conducted to evaluate the effect of temperature on time to cut (TTC). Results revealed that for every unit increase in temperature (1°C), time to cut was reduced by 0.759 min. Additionally, extreme low and high TTC values at the lowest temperature tested showed further development and testing are needed. This thesis presents several novel methods and findings with direct application to one of Canada’s most economically important fisheries and the innovation of entanglement mitigation devices.
General Summary
One of the biggest causes of mortality and injury for critically endangered North Atlantic Right Whales (NARW) in Canada and the US is entanglement in fixed fishing gear (e.g., lobster and snow crab gear). The lobster and snow crab fisheries are the most important fisheries economically to Canada, with landings of $1.8 billion and $1.4 billion, respectively in 2022. This highlights the importance of ensuring these fisheries remain sustainable by reducing their impact on other species. One option for entanglement mitigation is the utilization of Low Breaking Strength (LBS) components in buoy lines (between surface buoys and the first trap) while fishing. These components are designed to break when 1700lbf is applied. However, they need to be strong enough to withstand standard hauling loads while fishing. The Newfoundland and Labrador (NL) snow crab fishery is a deep fishery with heavy trawls (up to 100 traps per trawl), and harsh sea conditions and currents.
Without certainty that they are strong enough to be integrated into trawl fisheries like this one, their implementation could result in catastrophic environmental consequences in the form of ghost gear and ghost fishing. My research aimed to quantify the tension applied to down ropes while snow crab fishing in NL. Overall, this research is expected to inform decision-makers and engineers on considerations that should be made when developing entanglement mitigation measures for this fishery. Additionally, the tension data collected can inform other research endeavours or gear engineering for similar fisheries globally by providing tension data for the retrieval of baited fleets of traps and investigating the role of different environmental conditions and components of traps in the creation of tension while hauling.
We also performed a controlled benchtop laboratory study to evaluate the performance of a type of double-threshold entanglement mitigation device called a time tension line cutter (TTLC). These devices are also inserted in buoy lines and designed to sever the line when sufficient tension is applied for a designated amount of time using a hydraulic piston system. This mechanism was developed to allow harvesters to safely retrieve their gear without risk of breakage in heavier fisheries with loads exceeding 1,700 lbf while hauling. Based on prior studies and the use of an oil-like hydraulic fluid within TTLCs, we hypothesized that the viscosity and time to cut (TTC), would be temperature-dependent. The purpose of the study was to measure the effect of temperature on the device and evaluate if it affects its suitability for North Atlantic fisheries and performance as an entanglement mitigation device.
How temperature affects the TTC of TTLCs must be evaluated to avoid TTCs outside a reasonable expected range. If TTCs are lower than the bottom limit of the range, TTLCs may sever lines while hauling which would be a safety concern for harvesters on deck and may result in lost gear, posing further economic and environmental risks. If the TTCs are over the higher limit of the reasonable range, they may prolong entanglement and suffering, therefore increasing the risk of serious injury and mortality of entangled whales, i.e., they would not be practical nor have conservation benefits. This is why the effect of factors like temperature on their functioning must be properly understood so that they may be adjusted before fishery integration. Overall, this research aims to gain information on the functioning of TTLCs and identify areas where the mechanism could be improved or refined to better fit into fisheries while ensuring harvester safety and entanglement mitigation.
While this technology shows promise for integration in fisheries where traditional LBS inserts are not suitable, they are simply a mitigation method and do not prevent or reduce the risk of entanglement. They could, however, provide a temporary solution until prevention methods are developed. Ultimately, preventing entanglement by removing ropes in the water column while fishing (i.e., on-demand fishing gear) is the most effective way to reduce interactions between whales and fisheries and promote NARW recovery.
Find a few great resources on NARWs and entanglement mitigation below.
Load-cell installed above the hauler on a commercial snow crab fishing vessel used to measure tension while fishing
Time-Tension Line Cutter attached to a Tensile Test Machine to measure the time to cut.
Time-Tension Line Cutter inserted into a buoy line. The line does not need to be cut to install the device.
External Links
A few of my favorite resources for more information on North Atlantic Right Whales and information relating to this research.
