Research

SEASWAP Research has focused on key questions:

1.  How do sperm whales locate the longline deployment?

2.  What strategy do sperm whales use to take fish off, or depredate the line?

3.  How are whales finding particular fish of interest, particularly at night?

Through cooperative research with fishermen, government, and scientists the ultimate goal of this study is to provide recommendations for strategies to reduce or eliminate depredation on longline gear by sperm whales.

As a first step towards this goal, information was collected, in collaboration from the fishing fleet, on the timing of interactions seasonally and diurnally, with identification of the sperm whales occurring on the fishing grounds through visual photographic identification and genetic tissue samples.

This research helped define the scope of the problem, understand the ecology of this endangered species, as well as provided baseline information needed for studying depredation mechanisms, cues and, finally, developing solutions to reducing negative interactions.

Sperm whales are often sighted in waters at the continental shelf edge in Alaska, and the fishing port of Sitka is uniquely situated with ready access to these grounds.  Sablefish occur on the continental slope and most commercial longliners fish for sablefish in water depths between 250-600 fa (125-300m).  The continental shelf off Kruzof, Baranof and Chichagof islands is very narrow; consequently, the sablefish grounds are only 12-20 miles from shore in this area.

The Sitka-based Alaska Longline Fishermen’s Association (ALFA) has taken a proactive conservation approach to try and develop a deterrence system before mortalities occur.  Although this research is conducted in the eastern Gulf of Alaska, the results will be communicated wherever interactions occur.

STUDY AREA

Sperm whales are often sighted in near coastal waters of Alaska, and the fishing port of Sitka is uniquely situated with ready access to interactions.  Sablefish occur on the continental slope and most commercial longliners fish for sablefish in water depths between 1200’ and 3,000’.  The continental shelf off Kruzof, Baranof and Chichagof islands is very narrow; consequently, the sablefish grounds are only 12-20 miles from shore in this area.  Sitka is an ideal location to launch this project as the fishing grounds are easily accessible and much of the fleet (primarily vessels less than 60 feet) is based out of Sitka.

RESEARCH GOALS

We know that sperm whales are taking sablefish off longline hooks, but how?  The questions below are of particular interest, and this study attempted to answer them with the help of acoustics.

1. How do sperm whales locate the longline deployment?  For example, are the animals already present in an area when fishing vessels arrive, or are they attracted by sounds produced by the fishing vessel during deployment, or even attracted by sounds made by shifting fishing gear after deployment?
2. What strategy do sperm whales use to take fish off, or depredate the line?  Do any whales dive to the bottom to remove fish before the fishing vessel arrives, or do they wait to pick fish off the line as the gear is being hauled in?  At what depths are they taking the fish?
3. How are whales finding particular fish of interest, particularly at night?  If they are making sounds to locate fish, from how far away can they detect fish, and what is their “hunting” strategy?  How could their “success” rate be reduced?

UNIQUE FLUKES

An important part of sperm whale research is identifying individuals. That process includes photographing individual whales in the research area, and matching the photos with genetic samples. Individual sperm whales are identified by the unique markings on their backs, sides and undersides of their flukes, and by the shape of the dorsal fins and flukes. These markings are as unique as fingerprints.

The researchers chartered a small, high speed vessel to allow the primary investigator (PI) to take photos and collect genetic samples from sperm whales in the research area. Longline fisherman participating in the study helped the researchers find whales by calling in when they spotted sperm whales on the fishing grounds. Researchers then motored out to the area reported by the fisherman and located the whales using a directional hydrophone. Fishermen also allow SEASWAP researchers to accompany them on their commercial vessels during fishing trips, to collect identification photos of individuals.

Researchers photograph the sperm whales with either a 35mm SLR loaded with high speed black and white film, or a digital camera. Both are equipped with a 300mm telephoto lens. The researchers take field notes on the whales’ behavior, group size, surface activities, dive duration, and level of interaction with gear. Each whale’s information – behavior, photos and skin sample – is entered into a computer database. The best photograph of each individual whale is printed and used in the final sperm whale catalog of individuals. Individual photographs are then compared to all available sperm whale photographs, including catalogs from other areas, to determine if the whales sighted are different or the same whales.

The Gulf of Alaska Sperm Whale ID Catalog has 110 unique individuals at the start of the 2014 field season. A discovery curve shows the rate of new whales being “discovered” or photographed for the first time, is decreasing. This indicates that the SEASWAP team is close to having photographs of most individuals in the Eastern Gulf of Alaska near the study site of Sitka.

Photo caption: GOA-114, photographed by SEASWAP collaborator John Calambokidis on a SEASWAP tagging cruise with Cascadia Research Collective. Copyright SEASWAP 2009.

Photo caption: SEASWAP researcher Nellie Warner collects biopsy samples from the NOAA sablefish survey vessel F/V Alaskan Leader, 2006

An important part of sperm whale research is identifying individuals. Comparing genetic profiles is an excellent way to not only identify individuals, but also to understand family relationships between the whales.

Many questions exist regarding sperm whales in the Gulf of Alaska:

1. To which stock do these individuals belong?
2. How many individuals are involved?
3. What is the relatedness of individuals within groups following particular vessels, and what is the relatedness among groups in the area? And finally,
4. What is the gender of the depredating animals?

The SEASWAP researchers collected skin samples for their genetic tests. Sperm whales commonly slough off skin when they dive. A dip net can scoop skin samples right off the water. But if there is no sloughed skin, researchers can get a small sample (smaller than a pencil eraser) using a biopsy dart shot from a crossbow that grazes the surface of the whale. Some researchers have even used a small piece of stiff scrubby sponge tied onto the end of a pole and scrubbed skin onto the sponge.

The Southwest Fisheries Science Center (SWFSC), which has a library of 750 sperm whale samples from around the world, analyzed the newly collected skin samples.To date, here’s what the SEASWAP team has found:

– 26 samples have been collected in the Gulf of Alaska

– All samples have been genetically identified as male sperm whales

– Samples have come from 13 known individuals, and 13 unknown individuals (no photograph to match individual to catalog number)

Photo Caption: A biopsy dart collects a sample from a sperm whale in the Gulf of Alaska. Copyright SEASWAP, 2004.

VOCAL HUNTING

In 2003, hydrophone-equipped researchers working on the Southeast Alaska Sperm Whale Avoidance Project (SEASWAP) found that sperm whales are vocally active around fishing boats setting out and hauling in longline fishing gear. The sperm whales make short pulses called ‘clicks’ that seem to allow them to navigate, detect, and forage on individual prey items —in this case, hooked fish. Scientists think certain sounds of longline fishing may actually be attracting the whales. To find out if that’s true, researchers used an acoustical monitoring system to listen in on longline deployments and recoveries.

Long-term acoustic monitoring and tracking has traditionally been expensive, due to the costs of building, deploying, and retrieving an array large enough to detect and track sounds of interest over a few kilometers range.  The researchers came up with an elegant solution – use the longline fishing gear itself as the anchor for an acoustical array.

ACOUSTIC TAG

They also used the newest stand-alone, or autonomous acoustic recorders available. The recorder weighs less than half a pound and has the ability to record continuously for up to 17 hours to a 1 GB Flash card. Sperm whale sounds produce a surface-reflected path, or “echo,” from the ocean surface that can be used to locate the animal while using only two acoustic sensors.  The array not only detects sounds, but also tracks sperm whales in two or even three dimensions.

A longline vessel out of Sitka was chartered to do the acoustical work.  The vessel set out the standard longline fishing gear along the ocean bottom, but when the final anchor was lowered, three recorders spaced 2 meters and 100 meters apart were attached to the anchor rope with electrical tape.  They floated at a depth of 200, 198, and 100 m in the water column. The vessel then left the vicinity, leaving the instruments to record any sounds around the set longline gear.

Eight to 20 hours later, the boat returned and retrieved the longline gear and the recorders attached to it.  The anchor line without the instruments was hauled in first to permit the vertical array to monitor the acoustic behavior of any whales in the vicinity of the longline as it was retrieved.  Finally, the last anchor rope and instruments were recovered.  This process was repeated every couple of days over a 3-week period.

The acoustic arrays have shown that the sperm whales appear to be foraging at around 50m when in the vicinity of longlines in the water, whereas they forage at around 250m when no longlines are in the water. It also appears that the sperm whales are attracted to the longline vessels when they were pulling their gear from the water by the noises the engine made while being engaged and disengaged, not by sounds made by the gear or hydraulic winches.

LOGBOOKS

This study is a team effort. In a proactive move, longline fishermen out of Sitka brought the problem to the attention of managers and scientists. Now working on the problem, scientists are including interested longline fishermen in the process of finding answers. One of the ways fishermen are helping is through the SEAWAP Logbooks.

SEASWAP stands for Southeast Alaska Sperm Whale Avoidance Project. The core team includes ten skippers with vessels and crew who have agreed to be the eyes of the scientists while they’re at sea fishing. These fishermen keep a logbook of their sightings and interactions with sperm whales. They count the number of mutilated fish pulled off their lines and note if it looks like sperm whale depredation. The logbook includes pertinent information about their gear and fishing activities, including vessel type, hull type, electronics used and hydraulic system. The fishermen also photograph individual whales and their interactions using weatherproof cameras and film provided by the study. The logbook pages are collected after each fishing trip and summarized into a report by Linda Behnken, director of the Association of Longline Fisherman’s Association and passed on to the researchers.

In addition to the logbooks, participating fisherman are also part of a communications network, radioing the project base station when whales are sighted off Kruzof or Chichagof islands. And when possible, the fishermen collect residual fish parts, if depredation occurs at the surface, and the sloughed skin of sperm whales, if the opportunity arises, using study-issued long handled dip nets.

Team members completed training in photography and data collection, and are compensated for their time and effort.

RESULTS

Collaboration with fishermen gained insight into how many whales were involved, their sex, what fishing behaviors and acoustic cues* may lead to depredation. We found: a median of 90 male sperm whales were present in our study area who actively remove fish from longline gear, if whales are present at the haul there is a high likelihood of depredation, however there is a seasonal effect (reduced early in the season),One-third of all monitored sets (n=124) had whales near the longline gear during the set, soak or haul. Of the hauls with whales, 71% had some evidence of depredation. Depredation was lowest in March and highest during mid summer.

Based on these observations we have derived six low-cost depredation reduction techniques that we propose to quantitatively test over the next two years:
minimize engine cycling while hauling, which seems to attract animals,
deploying anchor lines that have no fishing gear attached (decoys),
acoustic monitoring with a low-cost hydrophone from fishing vessels prior to setting gear,
testing of an existing variant of fishing gear that includes acoustic reflectors and shortened gangions,
changing the time of year the fishermen deploy their gear and
retaining offal onboard until the end of the haulback.

Tentative acoustic observations:

How are whales finding gear?
No distinctive sounds by longline alone or hydraulics
Strongest candidate: way boat is handled
Detection range analysis requires bathymetry (added 2005)

How are whales taking fish?
Visual or acoustic? Very active acoustically
What depth are they taking fish? 50 m vs. 250 m
Are whales targeting dropped fish? Probably

Is avoidance a viable strategy?
Whale detection range at least 10 nm

Findings of SEASWAP have been significant:

Using acoustic recorders SEASWAP found sperm whales are alerted to fishing operations by the propeller cavitation sounds made when vessels shift in and out of gear while hauling longlines. This sound travels great distances, and whales can hear this sound from miles away.

SEASWAP captured a whale on video camera at depth fishing off the longline which gave us insights beyond our imaginations as how removal occurs. We suspended a camera on the longline after recovery and kept some of the catch on the line and redeployed the gear. A whale approached the line, grabbed it with its mouth and created tension by moving up the line. This tension created by these actions popped a fish off the line and the whale extracted itself from the line and swam after the unhooked fish.  Note that while the whale looks to be spinning on the line, this effect is actually created by the camera spinning.

It is difficult to estimate the loss of fish due to depredation. Estimates of fish loss are generally conservative because it is not possible to attribute an empty hook (because the bait could have been removed or disintegrated or fallen off the hook) to depredation. Additionally it can be difficult to distinguish whether other species, such as sharks, have contributed to the damage or loss of hooked fish. Damage and loss of fish has significant economic and management implications for both fisherman and fishery biologists tasked with assessing fish stocks. In general, depredation by sperm whales seems to be low to moderate, but it is highly variable in extent both among and within fishing areas. The variability became evident the first few years of SEASWAP when fishermen recorded details of fishing effort in logbooks. These data showed catch was higher when whales were present. Sperm whales and fishermen both knew where the good fishing grounds were located. Locations with no whales present were not as productive for fishermen as areas where whales were present even if depredation occurred.

Mathias D, Thode A, Straley J, Calambokidis J, Schorr G, Folkert K (2012).  Acoustic and diving behavior of sperm whales (Physeter macrocephalus) during natural and depredation foraging in the Gulf of Alaska. J Acoust Soc Amer 132:518-532

Straley J, O’Connell V, Behnken L, Mesnick S, Liddle J (2005) Sperm Whale and Longline Fisheries Interactions in the Gulf of Alaska NPRB Project R0309 Final Report

North Pacific Research Board, Anchorage, AK p 14

Thode A, Straley J,Tiemann C, Teloni V, Folkert K, O’Connell T, Behnken L (2007) Evaluation of sperm whale deterrents. North Pacific Research Board Final Report F0527 p 57

Hill, P.S., Laake, J.L., and Mitchell, E. (1999). Results of a pilot program to document interactions between sperm whales and longline vessels in Alaska waters. NOAA Technical Memorandum NMFS-AFSC-108. US Department of Commerce. Pp 51.

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Thode, A.M., Straley, J.M., Tiemann, C.O., Folkert, K., and O’Connell, V. (2007). J. Acoust. Soc. Am. 122, 1265-1277.

Mathias, D.K., Thode, A., Straley, J., and Folkert, K. (2009). Relationship between sperm whale (Physeter macrocephalus) click structure and size derived from videocamera images of a depredating whale (sperm whale prey acquisition). J. Acoust. Soc. Am. 125, 3444-3453.

Thode, A.M., Skinner, J.S., Scott, P., Roswell, J., Straley, J.M., and Folkert, K. (2010). Tracking sperm whales with a towed acoustic vector sensor. J. Acoust. Soc. Am. 128, 2681-2694.

Mathias, D.K., Thode, A.M., Straley, J.M., Calambokidis, J., Schorr, G.S., and Folkert, K. (2012). Acoustic and diving behavior of sperm whales (Physeter macrocephalus) during natural and depredation foraging in the Gulf of Alaska. J. Acoust. Soc. Am. 132, 518-532.

Mathias, D.K., Thode, A.M., Straley, J.M., and Andrews, R.D. (2013). Acoustic tracking of sperm whales in the Gulf of Alaska using a two-element vertical array and tags. J. Acoust. Soc. Am. 134, 2446-2461.

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Straley, J.M., O’Connell, V., Liddle, J.B., Thode, A.M., Wild, L.A., Behnken, L., Falvey, D., Lunsford, C. (2015). Southeast Alaska Sperm Whale Avoidance Project (SEASWAP): A successful collaboration among scientists and industry to study depredation in Alaskan waters. ICES J. Mar. Sci. 72(5), 1598-1609. doi: 10.1093/icesjms/fsv090100