A comparative analysis of the behavioral response to fishing boats in two albatross species

By Andriana Fragola, SRC Intern

This paper examines the behavior of the Wandering Albatross (WA) and Black-Browed Albatross (BBA), and how they are affected by the toothfish longline fleet in Kerguelen and Crozet (Collet et al. 2017). To do this, lightweight GPS loggers were attached to adult albatrosses of both species to track their movements. To track the fishing boats, VMS data was provided to the researchers which allowed them to log their movements (Collet et al. 2017).

Calculations were done to establish the maximal distance that birds were seen flying towards the fishing boats. To isolate the different behaviors of the albatross the researchers established “encounter” as well as “attendance” behaviors to assess the responses of the birds to these fishing vessels (Collet et al. 2017). Encounters were defined as more by chance when the birds were in flight, while attendance behavior was defined as sitting in the water within a close range of the vessels (Collet et al. 2017).

Figure 1

[Source: Collet et al. 2017]

Results demonstrated that the Black-Browed Albatross (BBA) did not come into contact with fishing vessels as often as the Wandering Albatross (WA) (Collet et al. 2017). BBA also seemed to forage in areas that were a greater distance from the fishing vessels than WA (Collet et al. 2017). When the vessels were absent, BBA were not seen foraging in the regions where the vessels typically operate, while WA were (Collet et al. 2017).

Although WA are the larger and more dominant species, they were not observed pursuing the fishing vessels as much as the researchers had expected (Collet et al. 2017). BBA had an 80% chance of being attracted to fishing vessels, while WA had a lesser 60% chance of being attracted to the boats (Collet et al. 2017).

There were apparent differences between these two species and their utilization of fishing fleets as a means for foraging (Collet et al. 2017). This paper suggests that the energetic needs of each species can be an indicator of the risks associated with foraging from anthropogenic sources (Collet et al. 2017).

Figure 2

[Source: Collet et al. 2017]

It is vital to understand how species are becoming reliant on anthropogenic sources for food because this can affect their nutritional health. The quality of the fish that albatross are getting from these fishing vessels may not have the nutritional value of the fish they typically hunt. Further, if generations of these animals become dependent on these unnatural food sources, this can lead to issues – if the availability of that source becomes compromised, and birds are reliant to the extent that they do not have the skill to forage on their own.

Work Cited

Collet, J., Patrick, S. C., & Weimerskirch, H. (2017). A comparative analysis of the behavioral response to fishing boats in two albatross species. Behavioral Ecology, 28(5), 1337-1347.

Horizontal and vertical movements of white marlin tagged off the Yucatan Peninsula

By Luisa Gil Diaz, SRC Intern

In “Horizontal and vertical movements of white marlin, Kajikia Albida, tagged off the Yucatan Peninsula”, Vaudo et al research the ecology and habitat use of white marlin to improve management measures, particularly within fisheries. White Marlin are a highly migratory and prized sport fish that has recently come under threat. Annually, 10,000 are caught in the United States. However, the highest source of white marlin mortality is when they are bycatch in loglines intended for swordfish and tuna. These billfish are being unintentionally killed off at unacceptable numbers, and while management policies have been implemented, they have focused on quotas and the practice of releasing individuals (Graves and Hordosky, 2015) and have not been very effectual. In fact, “The stock [of white marlin] is currently considered to be overfished with biomass believed to be half of that necessary to achieve maximum sustainable yield” (ICCAT, 2014). Vaudo et al’s study seeks to learn about the way white marlin use their habitat by tagging and tracking them, in order to determine where and how fishing should be allowed.

Image 1

The white marlin is a prized sports fish of conservational concern.

Image 2

A longline consists of a long line with many hooks, it does not discriminate between species and can lead to much bycatch.

To conduct the study, 21 white marlins were captured off the eastern Yucatan peninsula between May of 2014 and June 2016. The marlins were brought on board, and a pump was inserted into their mouths to ventilate their gills with salt water (just like we do!). On board, lower jaw fork length measurements were taken, and pop up satellite transmitting tags were inserted onto the dorsal musculature of the white marlin using an umbrella tag. The pop up tags transmitted information about depth, temperature, and light levels once detached from the Marlin after 365 days. Using the information from the tags, temperature-depth profiles were created, indicating the different temperatures present at different depths throughout the marlin’s habitats. Due to technological limitations, involving the satellite tags, there were some gaps in the data, but enough was collected for data analysis.

Image 3

The Marlin were seen around the Gulf of México, the Caribbean and the northwest Atlantic Ocean (Source: Vaudo et al. 2017).

Using the temperature-depth profiles, analysis on daily temperature profiles the Marlin spent time at were categorized into sets of discrete thermal habitats. The habitats were labeled Habitat A-Habitat G. Maximum daily depth, number of dives, dive length, and dive depth were analyzed at these habitats. Habitat A was the warmest, and the habitat at which the most time (29.5%) was spent daily. It was found that the use of certain waters decreases as cold increases. In fact, 98% of time was spent at waters warmer than 18 degrees Celsius. Temperature also had an effect on the vertical distribution of the swordfish. In warmer waters, dives were deeper and longer. At night, when the water column gets colder, the Marlins stayed within the upper 10 M. These patterns were seen across water columns of different thermal structures across the western Caribbean, the Gulf of Mexico, and the northwest Atlantic. It has been suggested that the reason for this is that the marlins’ are avoiding crossing sharp temperature discontinuities, and that’s why they stay along sub tropical water with a weak thermocline.

This study suggests that the implementation of minimum hook depths for longlines could prevent some Marlin bycatch. It would be an economically feasible strategy that could save. Shorter hooks in the warmer regions were Marlin’s spend more time in deeper water is an easy modification and would be effective in certain areas.

Works Cited

Vaudo, J. J., Byrne, M. E., Wetherbee, B. M., Harvey, G. M., Mendillo, A., & Shivji, M. S. (2017). Horizontal and vertical movements of white marlin, Kajikia albida, tagged off the Yucatán Peninsula. ICES Journal of Marine Science.

ICCAT. 2014. Report for the Biennial Period 2012–13, Part II (2013). International Commission for the Conservation of Atlantic Tunas. Madrid, Spain. 2. 349 pp.

Hoolihan, J. P., Luo, J., Snodgrass, D., Orbesen, E. S., Barse, A. M., and Prince, E. D. 2015. Vertical and horizontal habitat use by white marlin Kajikia albida (Poey, 1860) in the western North Atlantic Ocean. ICES Journal of Marine Science, 72: 2364–2373.

Towards more efficient longline fisheries: fish feeding behavior, bait characteristics and development.

By Sarah Hirth, RJD Intern

There has been a growing demand for bait resources seeing that standard bait types, such as squid, herring and mackerel are also used for human consumption. As a result, bait prices have increased, thus increasing the demand for an alternative bait, one that is not based on resources used for human consumption. This study highlights factors that need to be taken into consideration when looking for alternative bait, and explores attempts of alternative baits that have been made.

Løkkeborg at al. agree that an alternative bait should be “effective, species- and size-selective, practical for storage and baiting, and based on low-cost surplus products.” An alternative bait that would meet all of these characteristics would also make the procedure of longline fishing more environmentally friendly.

Although there have been several attempts to develop alternative baits, these have had limited success (e.g. Bjordal and Løkkeborg 1996; Januma et al. 2003; Polet al. 2008; Henriksen 2009). There have been two main methods, which have been used to create the alternative bait. These are natural resources, such as surplus products from the fishing industry and synthetic ingredients as attractants. Mentioned types of alternative bait are: Norbait, artificial bait invented by William E.S. Carr, bait bags, and arom bait.

Table 1

When these baits were tested, they all resulted in some positive factors. However, they still had undesirable outcomes. For example Norbait, which is based on surplus products, where minced fish products are mixed with alginate (a gelling agent, used as the binder) and extruded into a fiber mesh tube, has resulted in species –selective effects. In fishing trials Norbait has resulted in increased catch rates of two to three hundred per cent for haddock, yet Norbait compared poorly to natural bait for cod. “Compared to natural bait, minced herring enclosed in a nylon bag resulted in a 58% higher catch rates for haddock, a non-significant catch increase for tusk and ling, and a considerably lower catch rate for cod.” Similar results were observed with the other types of alternative baits.

The efficiency of longline baits depends on several factors, which are important to take into consideration when finding alternative baits. Some factors include: bait size, texture, and taste. An alternative bait also needs to be based on an odor source, and attractants need to be released over a considerable period of time. Løkkeborg et al. state that “the knowledge of food search behavior in fish is the basis of bait development efforts.” The list of factors affecting feeding behavior in this review includes: temperature, feeding motivation and hunger state, diel, tidal and annual rhythms, light levels, seasonal change in photoperiod, and water currents.

Figure 1

Although there currently are no alternative baits used in longline fishing, Løkkeborg et al. hope that improved knowledge of how fish respond to baited gear will aid future research aimed at the development of alternative baits. As the demand for marine resources for human consumption continues to increase, costs for longline bait are also likely to keep increasing. “The development of alternative baits used on resources not used for human consumption may therefore prove to be critical to a viable longline fisheries.”

Løkkeborg, S., et al. (2014). “Towards more efficient longline fisheries: fish feeding behaviour, bait characteristics and development of alternative baits.” Reviews in Fish Biology and Fisheries 24(4): 985-1003.

Challenges in seabird by-catch mitigation

By Hanover Matz, RJD Intern

In this paper, the authors comment on the current conservation status of seabirds and attempts to limit seabird deaths due to by-catch. Two species of seabirds, the albatrosses and the petrels, are particularly vulnerable to the detrimental effects of fisheries such as longlining. These birds normally lay only one egg per clutch and breed infrequently. They have long maturation and generation times compared to other birds, making it more difficult for their populations to recover from high mortality. They are also capable of flying long distances in search of food, crossing many different marine environments. This makes it difficult to implement conservation methods that can protect these birds in every part of the world they inhabit. Some of these species are already considered endangered or critically endangered. In order to fully protect them, an international effort is necessary.

A wandering albatross (Diomeda exulans) off Tasmania, Australia. Photo courtesy of JJ Harrison via Wikimedia Common

A wandering albatross (Diomeda exulans) off Tasmania, Australia. Photo courtesy of JJ Harrison via Wikimedia Commons

Seabirds and human fisheries come into conflict in many of the most productive regions of the ocean, specifically around New Zealand and Australia, the Humboldt Current off Chile, Peru, and Ecuador, the North Pacific, and South Africa. Seabirds are known to be killed as accidental by-catch in longline fisheries, and growing evidence has shown incidental catch of seabirds by trawlers. One difficulty in assessing whether trawling or longlining presents a greater threat to seabirds is the low proportion of entangled seabirds actually recovered from trawling gear. If the birds that collide with the gear cannot be retrieved, it is hard to assess the impact the fishery has. Refining the collection of data on how many seabirds are killed by longlining and trawling will improve conservation efforts.

In South Africa, the use of bird-scaring lines (BSLs) in fisheries has been shown to reduce the mortality of seabirds up to 95%. The trawl fishery previously had proportionally high incidental catches of albatrosses, making this a significant success in terms of protecting threatened species. However, to fully determine how well seabird mortality has been reduced, better data needs to be collected on both the level of by-catch and fishing effort. To reduce the by-catch of seabirds and improve conservation worldwide, the authors stress four important strategies. First, mitigation methods need to be improved with better data and techniques, considering each fishery individually and adapting the methods as necessary. Second, the quality of data collected needs to be increased by improving the programs used to collect it. Third, the fishing industry needs to be engaged by implementing and enforcing by-catch reduction, as well as cooperating to suit the needs of both the fishery and conservation. Finally, cooperation between governments, administrators, and decision makers is necessary to promote better fishing practices and conservation measures. In some fisheries, seabird by-catch mitigation is minimal or nonexistent. While trawling and longlining have been addressed, the effects of purse-seine and gill net fisheries are poorly understood. The threat posed by small scale and artisanal fishing fleets has also not been widely considered. If threatened seabird species are to be protected, it will require both national and international efforts. By improving the science behind the conservation, and cooperating with both governments and fisheries, scientists and conservations will be better able to address this conservation issue in the coming future.


1. Favero, M., & Seco Pon, J. P. 2014. Challenges in seabird by‐catch mitigation. Animal Conservation, 17(6), 532-533.



Economic vs. Conservation: Trade-offs between Catch, Bycatch, and Landed Value in the American Samoa Longline Fishery

By Laurel Zaima, RJD Undergraduate Intern

Commercial fisheries have prioritized maximum economic profit over the ecological distresses caused by their fishing practices. Consequently, unsustainable fishing practices hook high amounts of bycatch in relation to the amount of the target species. Bycatch are the animals that are accidentally caught and discarded due to lack of value, insufficient size, damaged, or regulatory reasons. Bycatch has detrimental effects on the populations of a diversity of marine species; therefore, has altered ecological relationships and the economics of commercial fisheries. A seemingly obvious solution to this threat would be the implementation of commercial fishing gear that mitigates bycatch. However, this resolution results in trade-offs among the catch, bycatch, and landed value. In their scientific research paper, Trade-offs among Catch, Bycatch, and Landed Value in the American Samoa Longline Fishery, Watson and Bigelow (2013) assess the benefits and disadvantages of modifying longlines to reduce bycatch in the American Samoa longline.

Longline fisheries often modify their fishing gear to the behavior characteristics of their target species in order to have the most catch per unit effort.  Shallow hooks (<100 m) would be set to target yellowfin tuna and billfish, where as, deep hooks (>100 m) will be set to target albacore and bigeye tuna. The U.S. longline fishery based in American Samoa target a majority of their valued species in deep water, such as albacore. Unfortunately, their current fishing practices are not modeled after the behavior of their target species and have led them to catch tons of bycatch. Non-targeted species, such as green sea turtles, silky sharks, and oceanic whitetip sharks spend majority of their life near the surface, and are susceptible to longlines set in shallow waters (<100 m) or hooks passing through the surface during the setting or retrieval of hooks. The elimination of shallow water hooks or the redistribution of shallow hooks to deeper depths could help reduce bycatch and increase the landing of target species.

Watson and Bigelow (2013) modified the American Samoa fishery’s longline fishing gear by removing the shallowest hooks per section of the longline or by hypothetically redistributing the shallowest hooks to a deep position. In the first three scenarios, Watson and Bigelow (2013) eliminated the first hooks, the first and second hooks, and the first, second, and third hooks at both ends of each section.  In the other three scenarios, the hooks were theoretically rearranged into deeper depths by extending the number of sections.

Picture 1

A Longline section has about 23-36 hooks between two floats, and each longline has up to ~100 sections. In Watson and Bigelow’s (2013) study, they modified the longline by either eliminating the shallowest hooks or by hypothetically reallocating them into deeper positions.

They found that there is a decrease in all catch, including a significant decrease in bycatch, by eliminating shallow hooks from longline sections. By reallocating the shallow hooks to deeper positions, there was an effective bycatch reduction while still sustaining target species landings. In terms of economic profit, it would be most beneficial for longline fisheries to redistribute their hooks to deeper positions because it increases their chances of catching the most valuable species. Specifically, there was an increase in catch of the three most valuable species in the American Samoa fishery, albacore, yellowfin, and bigeye tunas, with the redistribution of hooks. The increased catch of these 3 species alone would increase the total annual landed value by an estimated U.S. 1.4 million dollars.

In terms of conservation benefits, the removal of the first three shallow water hooks reduces bycatch for a variety of species, including 25 species of fish, sea turtles, billfishes, and some shark species. Although there are ecological advantages to the elimination or redistribution of the shallow water hooks, there are some economic trade-offs. In the scenarios of elimination and redistribution, there is a loss in landed value for wahoo, billfishes, and dolphinfish. However, the catch of tuna would probably compensate for the loss value of these species. There is also a possibility of an unintentional trophic cascade with decreased catches of billfish (tuna predators) because it could increase the predation on a fishery targeted tuna species. Another potential trade-off would be the increased bycatch of deeper dwelling vulnerable species, such as shortfin mako sharks and the bigeye thresher sharks.

Picture 2

A thresher shark is caught on a longline as bycatch.

Watson and Bigelow’s (2013) modifications to the hook distribution on longlines should be considered for implementation by longline fisheries that target deeper residing species. Depending on the location of the fishery, these longlines could have varying economic and ecological results. Nonetheless, adjusting the longline hooks to specifically target a species is the most feasbile way to reduce bycatch while sustaining target species catches.