Seamounts as foraging grounds for a marine predator, the Bulwer’s petrel.
(2024) BION02 20231Degree Projects in Biology
- Abstract
- Regularly described as hotspots for marine life, seamounts are important foraging grounds for marine predators. In surface waters over seamounts, diel vertically migrating organisms can be aggregated, making seamounts potentially attractive and profitable food sources for predators such as seabirds. Still, the potential association between seabirds and seamounts has seldom been described and little is known of the benefits foraging over the landforms might have on an individual’s fitness. Bulwer’s petrels are small seabirds that feed on mesopelagic fishes and cephalopods that can be aggregated in the waters over seamounts. In this thesis, I aimed to describe Bulwer’s petrels use of seamounts throughout the breeding season and investigate... (More)
- Regularly described as hotspots for marine life, seamounts are important foraging grounds for marine predators. In surface waters over seamounts, diel vertically migrating organisms can be aggregated, making seamounts potentially attractive and profitable food sources for predators such as seabirds. Still, the potential association between seabirds and seamounts has seldom been described and little is known of the benefits foraging over the landforms might have on an individual’s fitness. Bulwer’s petrels are small seabirds that feed on mesopelagic fishes and cephalopods that can be aggregated in the waters over seamounts. In this thesis, I aimed to describe Bulwer’s petrels use of seamounts throughout the breeding season and investigate whether foraging over seamounts could be related to a trip’s productivity and breeding success. GPS loggers were deployed on 285 individuals over 7 breeding seasons (2017-2023) in two colonies (Montaña Clara, Canary Islands, Spain; Ilhéu Cima, Cape Verde), recording a total of 1300 foraging trips. On a foraging trip, a Bulwer’s petrel travelled on average 1,035 kilometers (SD = 1,215, range: 104 – 6,322) over an average period of 2 days (SD = 3, range: 0.6 – 13.9). By identifying most likely foraging locations for each trip, I show that Bulwer’s petrels foraged over at least one seamount in 34% of the trips they took over 7 breeding seasons. In a trip, a Bulwer’s petrel foraged over an average of 3 seamounts (SD = 0.5, range: 1 - 14) around the Montaña Clara colony and 1 seamount (SD = 0.5, range: 1 - 5) around the Ilhéu Cima colony. Overall, Bulwer’s petrels from both colonies foraged over 120 different seamounts and spend proportionally more time foraging as they were over them as compared to away from them. Additionally, foraging over seamount was more likely during chick-rearing than during incubation and males were more likely to use seamounts than females. Differences between breeding stages and sexes may relate to specific nutritional requirements that Bulwer’s petrels need to meet by adapting their foraging strategies. Foraging over seamounts was not related to trip performance or breeding success and further work will be necessary to uncover the ways in which foraging over seamounts could benefit seabirds. However, this study highlights that GPS tracking allows for quantifying seabird’s foraging behaviour over seamounts, paving the way for new research on the association between seamounts and marine predators and the identification of most relevant seamounts for marine conservation. (Less)
- Popular Abstract
- A small seabird’s quest for food over “underwater mountains”
Have you ever heard of “underwater mountains” called seamounts? Seamounts can be pictured as mountains that are completely submerged in the ocean. They rise from the bottom of the ocean and their summits never cross the surface. Seamounts are often described as “hotspots for marine life”. This means that these fully submerged “mountains” can be places in the ocean where a lot of different species can be found, sometimes in great numbers. Because of that, seamounts can be good foraging places for marine predators such as sharks, large fish, seals, and seabirds. Unfortunately, human activities such as fishing and mining threaten the biodiversity around seamounts. To guide... (More) - A small seabird’s quest for food over “underwater mountains”
Have you ever heard of “underwater mountains” called seamounts? Seamounts can be pictured as mountains that are completely submerged in the ocean. They rise from the bottom of the ocean and their summits never cross the surface. Seamounts are often described as “hotspots for marine life”. This means that these fully submerged “mountains” can be places in the ocean where a lot of different species can be found, sometimes in great numbers. Because of that, seamounts can be good foraging places for marine predators such as sharks, large fish, seals, and seabirds. Unfortunately, human activities such as fishing and mining threaten the biodiversity around seamounts. To guide protection measures of marine life around seamounts, understanding seamount’s importance for animals like marine predators is essential.
Seabirds are marine predators that, to find food, can fly thousands of kilometers in just a few days. Because of the abundant fish and squid that can gather around seamounts, seamount might be very interesting foraging places for seabirds. Yet despite visual observations that seabirds forage over seamounts, we know little of the relationship between seabird and seamounts or of the benefits that feeding over a seamount might have for a seabird. In this thesis, I explored the importance of seamounts as foraging habitat for a small seabird species named Bulwer’s petrel. Bulwer’s petrels feed on the type of organisms that can be found in high numbers around seamounts, but it was unknown whether they used seamounts as a food source.
Uncovering seabird’s movements over the ocean
Seabird’s movements over the ocean can be precisely tracked with technologies called GPS loggers. Such GPS loggers were mounted on Bulwer’s petrels during the breeding season to reveal their trajectories and identify if they used waters above seamounts for foraging.
Did the petrels go over seamounts to feed, and did they benefit from it?
Bulwer's petrels did use areas above seamounts to forage. In fact, they did so regularly: in a third of the trips that they took during the breeding period. Interestingly, Bulwer’s petrels foraged over seamounts more often after their egg hatched and when they had to provide food to their nestling. Taking care of a nestling requires a lot of energy so the abundant food that the parents might have found over seamounts could explain why Bulwer’s petrels used seamounts most during chick-rearing. Additionally, males were more likely to feed over seamounts than females. This hints that, despite looking perfectly alike, males and females might have played different roles in raising their offspring and exploited different food sources.
Surprisingly, I could not identify any benefits from feeding over seamounts. Feeding over seamounts was not related to weight gain of the bird during a trip, which would have indicated that the bird found a lot of food over seamounts. Neither was foraging over seamounts related to reproducing successfully. However, it cannot be excluded that there might have been other ways in which feeding over seamounts benefitted Bulwer’s petrels, for example that foraging there was beneficial for their health and increased survival.
Take-home message(s)
If you ever hear about seamounts again, you should remember that they can be important feeding areas for marine predators such as seabirds. In the long run, a good knowledge of the importance of seamounts for marine predators will be essential for the conservation of both predators and seamounts.
Degree project in Biology, Aquatic ecology (45 ECTS)
Biology department, Lund University
Supervision: Jacob González-Solís (University of Barcelona), Fernando Medrano (University of Barcelona), Arne Hegemann (Lund University). (Less)
Please use this url to cite or link to this publication:
http://lup.lub.lu.se/student-papers/record/9154882
- author
- Deiss, Alice
- supervisor
- organization
- course
- BION02 20231
- year
- 2024
- type
- H2 - Master's Degree (Two Years)
- subject
- language
- English
- id
- 9154882
- date added to LUP
- 2024-05-28 13:24:18
- date last changed
- 2024-05-28 13:24:18
@misc{9154882,
abstract = {{Regularly described as hotspots for marine life, seamounts are important foraging grounds for marine predators. In surface waters over seamounts, diel vertically migrating organisms can be aggregated, making seamounts potentially attractive and profitable food sources for predators such as seabirds. Still, the potential association between seabirds and seamounts has seldom been described and little is known of the benefits foraging over the landforms might have on an individual’s fitness. Bulwer’s petrels are small seabirds that feed on mesopelagic fishes and cephalopods that can be aggregated in the waters over seamounts. In this thesis, I aimed to describe Bulwer’s petrels use of seamounts throughout the breeding season and investigate whether foraging over seamounts could be related to a trip’s productivity and breeding success. GPS loggers were deployed on 285 individuals over 7 breeding seasons (2017-2023) in two colonies (Montaña Clara, Canary Islands, Spain; Ilhéu Cima, Cape Verde), recording a total of 1300 foraging trips. On a foraging trip, a Bulwer’s petrel travelled on average 1,035 kilometers (SD = 1,215, range: 104 – 6,322) over an average period of 2 days (SD = 3, range: 0.6 – 13.9). By identifying most likely foraging locations for each trip, I show that Bulwer’s petrels foraged over at least one seamount in 34% of the trips they took over 7 breeding seasons. In a trip, a Bulwer’s petrel foraged over an average of 3 seamounts (SD = 0.5, range: 1 - 14) around the Montaña Clara colony and 1 seamount (SD = 0.5, range: 1 - 5) around the Ilhéu Cima colony. Overall, Bulwer’s petrels from both colonies foraged over 120 different seamounts and spend proportionally more time foraging as they were over them as compared to away from them. Additionally, foraging over seamount was more likely during chick-rearing than during incubation and males were more likely to use seamounts than females. Differences between breeding stages and sexes may relate to specific nutritional requirements that Bulwer’s petrels need to meet by adapting their foraging strategies. Foraging over seamounts was not related to trip performance or breeding success and further work will be necessary to uncover the ways in which foraging over seamounts could benefit seabirds. However, this study highlights that GPS tracking allows for quantifying seabird’s foraging behaviour over seamounts, paving the way for new research on the association between seamounts and marine predators and the identification of most relevant seamounts for marine conservation.}},
author = {{Deiss, Alice}},
language = {{eng}},
note = {{Student Paper}},
title = {{Seamounts as foraging grounds for a marine predator, the Bulwer’s petrel.}},
year = {{2024}},
}