Trade-offs Between Energy Maximization and Parental Care in a Central Place Forager, the Sea Otter

By Trish Albano, SRC Intern

Energy expenditure is a key component to consumer foraging strategies. In this study, the influence of prey availability and reproductive limitations were examined, in an effort to determine their impact on the foraging behavior of the southern sea otter (Enhydra lutris nereis). Theoretically, when food is plentiful, it is energetically efficient for a central place forager to exploit prey patches that are closest, therefore minimizing energy expenditure and conserving metabolic rate. The study predicts that as prey becomes more scarce, otters will dive deeper to find prey and the associated energy expenditure will be proportionately greater. Due to the physiological differences between males and females, the study predicts that males will show a greater range of dive depths and durations but both sexes will respond to prey scarcity in the same manner. The demands of pup care in females are also taken into account – it is hypothesized that if pup care plays a significant role in females’ diving behavior, mothers with small pups will stray from normal responses to food scarcity the most because deep, long dives could increase the likelihood of pup loss.

Mother sea otter with rare twin baby pups, presumed to have been born just one or two days earlier on June 23-24, 2013. Photo taken 24 June 2013, Morro Bay, CA. AKA Southern sea otter and California sea otter, Subspecies E. l. nereis, Coast of Central California. Wiki

A mother and pup Southern Sea Otter (E. I. nereis). It has been shown that mother sea otters put a considerable amount of energy into the parental care of their pups. Image credit: Wikimedia Commons


The researchers utilized TDRs (time-depth recorders) implanted in wild southern sea otters to collect data in 5 locations (Figure 1) (Monterey, Big Sur, San Luis Obispo County, Santa Barbara Channel, San Nicolas Island) along the California coast. TDRs stayed inside the animal for approximately 1 year. Most animals were observed from shore for behavioral data collection and it was noted that across all 5 sites, otters fed on 80 different species of benthic invertebrates. Both resource abundant (low otter density, high food density) and resource deficient (high otter density, low food density) sites were explored.

Figure 1: This figure shows the 5 sites that data was collected for Southern Sea Otter populations. In these locations, otters were fitted with TDRs and observed for study.

Figure 1: This figure shows the 5 sites that data was collected for Southern Sea Otter populations. In these locations, otters were fitted with TDRs and observed for study.


When prey was scarce, otters expanded their selection to include less-preferred prey. It was found that males and females without pups utilized similar foraging strategies and responses to food limitation, making deeper, longer and more energetically costly dives as prey became more scarce. However, females with pups were less likely to exhibit these energetically inefficient diving profiles. Mothers with young pups (less than 10 weeks old) placed parental care at higher priority than foraging when resource limitation would require them to perform energetically expensive dives that would reallocate their energy usage away from their pups. Females without pups in resource-abundant areas made 54% of dives to 2-5 m and 25% of dives to 6-10m whereas females with young pups made 3% of dives to 2-5 m, 52% of dives to 6-10 m, and 29% of dives to 11-15 m (Table 1). This trend of greater-proportion deeper dives was similar in resource-limited areas. This shows that females with pups utilized their energy in such a way that made it worth their while to leave their pups alone if there was a higher likelihood that they would be able to access food during their dive. Overall, the researchers’ hypotheses were supported by the data.

Table 1: This table shows the summary for TDRs that were used to obtain data in the study. The TDRs are site specific and measure resource availability, age range, median age, years of deployment, and duration of TDR recording.

Table 1: This table shows the summary for TDRs that were used to obtain data in the study. The TDRs are site specific and measure resource availability, age range, median age, years of deployment, and duration of TDR recording.


This study shows that prey availability is critical for all southern sea otters, but especially for mothers with pups. If resource abundance is depleted, it can become very risky and energetically expensive for otters to forage. This could cause an increase in pup mortality and become a threat to southern otter populations.

Thometz, N. M., et al. “Trade-offs between energy maximization and parental care in a central place forager, the sea otter.” Behavioral Ecology (2016): arw089.

A case for the importance and management of fish spawning aggregations

By Rachel Skubel, SRC Intern

Every year, at least 300 species of fish will go to a specific spot in the ocean, at a specific time, for a key event in the continuation of their species: spawning, or releasing eggs to be fertilized. Erisman et al. (2015) detail why these fish spawning aggregations (FSAs) are hotspots of productivity, and why they are intuitive areas to protect.

Over time, fish species come to regularly spawn at these locations in order to maximize fitness (i.e. the survival of their offspring, and thus the propagation of their genes). FSA sites are defined by geomorphology and oceanography that yield high productivity (i.e. upwelling around seamounts that bring nutrients and high primary production), allowing the eventual larvae to feed and increase chances in the larger ocean arena. Not only do spawning fish and their offspring benefit, but the influx of eggs (‘egg boon’) creates a nutrient-dense food source for other animals – this is an example of a ‘trophic cascade’ that can support the health of an ecosystem. Further, marine animals on a migratory route (such as whale sharks) can feed from the resulting feast – which means FSAs are important links between ecosystems. Typically timed with seasons and lunar cycles, many species (up to tens of species) will come to spawn at one FSA site.

Clearly, protecting FSAs is an effective conservation strategy – the benefits go far beyond the spawning species in question, and authorities receive a very high ‘bang for their buck’ so to speak. Protecting one area can replenish numerous species across their ranges. And yet, focused management strategies are lacking.

How do humans fit in the picture?

What with their being so predictably productive over a small area, there are many fisheries associated with FSAs – from commercial to recreational and subsistence. This illustrates the importance of proper management, as overexploiting a species in such a small space, during an important life history event, can impact the fish over a huge spatial and temporal range. The Nassau grouper (Epinephelus striatus) is an excellent example. Formerly a productive and important fishery species in the Caribbean, prolonged overfishing resulted in FSAs being extinguished across its territory. Now, it is listed as endangered by the International Union for the Conservation of Nature.

How are FSAs protected?

Less than 35% of known FSAs receive any amount of protection from marine protected areas. An estimated 52% of FSAs remain unassessed, and of the 906 documented sites (see Russell et al. 2014; Figure 1), most are at reefs and in tropical waters – meaning cold-water aggregations are ripe for discovery and protection. The congregation of so many individuals at a predictable time at one location means that FSAs are valuable for recurring stock assessment. The IUCN World Conservation Congress (circa 2014) recommended governments create management measures that would sustainably protect reef fish and their spawning aggregations, as well as directing NGOs and fishing management organizations to take up the issue. Due to their recurring nature, protection of FSAs is effective for many of the same reasons fishing them is – managers know just which times and places would be most effective for a fishery closure, and this closure is predictable for the resource users as well.


The global distribution of known fish spawning aggregations (Erisman et al. 2015, based on data from Science and Conservation of Fish Spawning Aggregations Global Fish Spawning Database

The global distribution of known fish spawning aggregations (Erisman et al. 2015, based on data from Science and Conservation of Fish Spawning Aggregations Global Fish Spawning Database

In Europe, the European Union’s Common Fishery Policy now directs the retention of a stocks’ full reproductive capacity to achieve ‘Good Environmental Status’, yet the UK’s Marine Management Organization may implement a spatial zoning approach that prioritizes fishing activity over other uses of a given area. In the US, the Magnusson-Stevens Act (MSA) recognizes FSAs as essential fish habitat (EFH), which fishery management bodies are mandated to minimize fishing impacts upon.

Continuing with the Nassau Grouper example, the Bahamian Government has implemented an annual closed season for the species from December 1st to February 28th to protect their spawning aggregations, which means that ‘taking, landing, possessing, selling, and offering for sale’ is prohibited, and can result in a fine of $5000 or a one-year imprisonment ( Dr. Kristine Stump of the Shedd Aquarium is currently studying these ecologically and economically important fish during their breeding seasonin the Bahamas, combining acoustic telemetry, genetic analysis, and blood sampling (

Going forward, the best chance for successful protection of FSAs may lie in community participation to ensure compliance by fishers. The Coastal Conservation Association in the US is composed of recreational fishers, who were in support of seasonal closures for the Warsaw grouper and speckled hind, realizing that this would allow them to fish the species at other times of the year, for years to come. Effective design is also important; in the Caribbean, the Caribbean Fishery Management Council and South Atlantic Fisheries Management Council aim to establish networks of reserves to protect reef species. Erisman et al. have made an excellent case for the protection of FSAs, and their potential to serve as a success story across conservation and fisheries sectors.


Works cited

Erisman, B., Heyman, W., Kobara, S., Ezer, T., Pittman, S., Aburto‐Oropeza, O., & Nemeth, R. S. (2015). Fish spawning aggregations: where well‐placed management actions can yield big benefits for fisheries and conservation. Fish and Fisheries. doi: 10.1111/faf.12132

Russell, M.W., deSadovy Mitcheson, Y., Erisman, B.E., Hamilton, R.J., Luckhurst, B.E. & Nemeth, R.S. (2014) Status Report – World’s Fish Aggregations 2014. Science and Conservation of Fish Aggregations, California USA. International Coral Reef Initiative.

Lifting, Not Shifting, Baselines in the Face of Conservation Success

By Kevin Reagan, SRC Intern

Twenty years ago the term “shifting baselines” was explored and coined by a fisheries scientist named Daniel Pauly in his paper titled “Anecdotes and the shifting baseline syndrome of fisheries.” This term is used to describe the idea that with each successive generation, in this case speaking of generations of fisheries scientists, the baseline (or standard) of fish stocks, abundance, size, growth rate, etc. is what they observed in the population at the beginning of their careers. Losses before this time are not really seen as losses because the norm is what’s observed when scientists begin, and this is not necessarily the case; in most instances that number is already far below what historic levels were and not the true baseline that would describe a healthy, fully recovered population. What is even worse is that it shifts with each generation, gradually moving farther away from where it should be and being considered fine.

However, in recent years, certain species of animals are recovering and growing in number, eventually returning to areas they had long been absent from. This is almost always a result of the reduction/banning of commercial hunting, like the Convention on International Trade of Endangered Species, and harmful chemicals like DDT. In this paper, authors propose the idea of “lifting baselines” as part of the shifting baselines syndrome to describe and celebrate conservation success stories. In analysis of trends of 92 different marine species, 42% were increasing in number, 10% were decreasing, and the rest showed no change in status. This is not to say that this is a universal trend; huge numbers of species are still in decline and we are still in the midst of a massive extinction event. Even so, many species are doing better than before. For instance, elephant seals were almost hunted to extinction in the late 1800’s. It is estimated that as few as twenty individuals remained. But, after being protected by Mexico and the U.S. in the 1920’s, their numbers have rebounded to over 200,000 seals.

Northern elephant seal rookery on Año Nuevo Island, CA. The graph depicts the increase in the number of births of elephant seals since 1960.

Northern elephant seal rookery on Año Nuevo Island, CA. The graph depicts the increase in the number of births of elephant seals since 1960.

While the recovery of species is great news for conservation scientists, it is not always welcomed by the public, especially recovery of marine predators. Many maritime industries developed while predators were few and far between and expected them to stay that way. Now that their numbers have rebounded, people believe there to be a surplus regardless of what the numbers were before exploitation (example of shifting baselines). This can result in a call for culling (mass killing) of the animals because they’re considered a nuisance. Lifting baselines, where “successful recovery of depleted species is verified, celebrated, and understood in an ecological and historical context,” can counter this. Authors developed four basic strategic recommendations to lift baselines, develop public support, and create acceptance in the sociopolitical arena around these success stories. They are as follows:

  1. When protection works, celebrate it!

– Conservation scientists and NGO’s need to actively engage the public in monitoring and recording a species’ return to its previous historic numbers. This creates a positive attitude and a sense of responsibility for the animal’s recovery.

  1. Down/delist species that no longer require protective measures

–  Reward the efforts that reversed the species’ decline and allow the time and resources previously being used to help those species that are still in trouble.

  • Actively anticipate and manage potential and actual conflicts that are the result of range expansion and trophic interactions of recovering species.

–  Monitor ecological changes and engage stakeholders as part of the recovery strategy. Recovering species will influence other species and the food web as it assumes its role in the environment. Investigating these relationships between species of concern will help develop realistic recovery targets and management goals

  1. True costs and benefits of removing “nuisance” animals through different means must be established.

–  In general, there is very little follow-up after the removal of nuisance animals and cost-benefit analyses are almost never performed. Costs should be quantified and include both ecological and social measures. If the methods used are not cost-effective, a less destructive and invasive approach is needed

These recommendations should be put in place while the initial conservation steps are being taken. Clear and realistic recovery goals can help species move off the endangered species list and accurate estimates of costs/benefits can turn wildlife from a scapegoat to an asset. However, this will require input from more than just scientists. Economists, artists, journalists, and social scientists will all be needed for effective public outreach and conservation measures, especially to reduce conflicts between humans and endangered animals. If we all work together, we can establish conservation plans that are practical, can make a difference, and most importantly, are realistic.


Roman, Joe, Meagan M. Dunphy-Daly, David W. Johnston, and Andrew J. Read. “Lifting Baselines to Address the Consequences of Conservation Success.” Trends in Ecology & Evolution 30.6 (2015): 299-302. Web.


Fishermen Views on Marine Protected Areas

By Alice Schreiber, RJD Intern

As fish stocks continue to decline, Marine Protected Areas are becoming increasingly popular methods of conserving marine habitats and preserving species. The success of these areas depends upon the existing legal framework, acceptance by the community, and an effective management system [1].

Image 2

Being aware of how fishermen socially perceive MPAs is crucial when establishing them and creating management guidelines. MPAs are established areas where fishing pressure is reduced by designating the amount of fishing effort, time available for fishing activity, species that can be caught, gear permitted, or catch limits [2]. At times, Marine Protected Areas may completely restrict fishing or some areas may be designated Marine Reserves which function as no-take zones. The expectation is that the MPA will “maintain or restore marine biodiversity and ecosystem function,” as well as “improve socioeconomic conditions by increasing revenues from fisheries production due to an increase in the size and number of fish migrating out of the MPA [3]”.  Without taking into account the stakeholders’ perception of the reserve, enforcing management of Marine Protected Areas would be nearly impossible.

A new study by Monalisa Silva and Priscila Lopez, sheds some light on how to determine fishermen’s perceptions of MPAs and what criteria influence the opinions the fishermen have about the MPA. When evaluating perception among fishers, four questions are asked: (1) if a fisherman born in a place subjected to the limitations of an MPA has a more conservationist attitude; (2) if young, part-time, non-selective fishers are more flexible and adaptable to changes in the reserves, (3) if full-time fishermen who were born in a community under the influence of an MPA have greater participation in the establishment of management; and (4) if fishermen born in a community under the influence of an MPA have more positive opinions than immigrant fishermen regarding the protected areas [2].

Asking these questions allows researchers and policy makers to understand which individuals within a community are less likely to comply with the regulations, and as such, which individuals would benefit from more education or incentives regarding the protected areas. Compliance will not be at adequate levels if there is not a proper understanding from the public of why MPAs are needed.

Three MPAs in the states of Rio Grande do Norte served as the location for the study, in which one hundred fishermen were interviewed. The fishermen were between the ages of 21 and 77 years old and had an average fishing experience of 29 years. They were split into four groups, depending on their age, birthplace, type of fishing gear, and their level of dependence on fishing. They then took a questionnaire, which assessed their perception of biodiversity conservation, flexibility and adaptability, participation in management, and opinions about MPAs.

Image 1

The results of this study were able to confirm that older fishermen using selective gear have a more conservationist perception, full-time fishermen who use selective gear have lower flexibility and adaptability, and older fishermen tend to have more positive opinions regarding the MPA [2]. Flexibility and adaptability are important in regards to MPA compliance. Selective fishing gear allows fishermen to target a specific species or size of fish and when that fish stock collapses or is not longer allowed to be fished, they have very little flexibility in their choices. Encouraging fishermen to work in other areas part-time or to explore different resources beyond fish may help to ease the lack of flexibility.

Taking into account stakeholder perception is extremely important for the proper and effective management of MPAs. Compliance issues result from misconceptions of the conservational goals and from heavy dependence on fishing as their primary or only income. Being considerate of these issues allows for more effective management of MPAs and a more positive perception from fishermen and the affected community.


Works Cited

Salm, Rodney V., John R. Clark, and Erkki Siirila. Marine and coastal protected areas: a guide for planners and managers. IUCN, 2000.

Silva, Monalisa RO, and Prisicla FM Lopes. “Each fisherman is different: Taking the environmental perception of small-scale fishermen into account to manage marine protected areas.” Marine Policy 51 (2015): 347-355.

Pomeroy, Robert S., et al. “How is your MPA doing? A methodology for evaluating the management effectiveness of marine protected areas.” Ocean & Coastal Management 48.7 (2005): 485-502.


71 Questions: A Guide for Marine Conservation

By James Keegan, RJD Intern

The ocean remains an immense resource for humanity, providing food, economic activity, and cultural roots for many. Although these resources are valuable, it is difficult to effectively protect them because our knowledge of marine ecosystems is lacking. To correct this insufficient understanding of the marine environment, Parsons et al. 2014 conducted two workshops in order to establish a list of important questions that would help direct conservation research.  If conservationists can answer these questions, the community’s ability to conserve and mange the world’s marine resources would substantially improve. With the contributions from participants in the fields of science, conservation, industry, and government, Parsons et al. 2014 identified 71 key questions for the preservation of the marine environment. They then grouped these questions into 8 categories, each associated with an aspect of marine conservation: fisheries, climate change, other anthropogenic (human caused) threats, ecosystems, marine citizenship, policy, societal and cultural considerations, and scientific enterprise. Using these questions as guidelines, funders and researchers can develop programs that can greatly benefit marine conservation.

Because oceans are vast, and their environments difficult to access, marine research is expensive and difficult to undertake. Expensive technologies necessary for accessing marine environments, like submersibles, raise costs beyond those typically incurred by terrestrial, or land-based, studies. Moreover, marine conservation research receives funding at a much lower rate than terrestrial conservation. In order to combat these issues, Parsons et al. 2014 sought out to identify a set of questions that, if answered, would contribute immensely to conserving marine ecosystems on a global scale, thus maximizing the returns of the research programs involved. By prioritizing the most important questions facing marine conservation, conservationists can more effectively protect the marine environment with the funding they receive.

A table showing example questions produced by Parsons et al. 2014 for each of the 8 categories.

A table showing example questions produced by Parsons et al. 2014 for each of the 8 categories.

In order to produce their list of key questions, Parsons et al. 2014 conducted a pair of workshops. In their first workshop, held during the second International Marine Conservation Congress (IMCC), 17 participants with varying expertise reviewed an initial list of 631 questions. Parsons et al. 2014 solicited these initial questions from participants at IMCC, professional peer groups, and the Society for Conservation Biology. The 17 participants reduced the number of questions to 316, and Parsons et al. 2014 voted on these remaining questions in their second workshop, ultimately reducing the number to 71. Finally, they grouped these 71 questions into 8 categories: fisheries, climate change, other human produced threats, ecosystems, marine citizenship, policy, societal and cultural considerations, and scientific enterprise.

A flow chart summarizing the steps taken in the workshops. (Parsons et al. 2014)

A flow chart summarizing the steps taken in the workshops. (Parsons et al. 2014)

Each of the 8 categories pose challenges to marine conservationists. Mass extraction of fish and other organisms stress marine ecosystems and can lead to overexploitation. Components of climate change, like warmer waters and ocean acidification, directly affect marine species and indirectly affect ecological interactions. Other human activities negatively impact marine ecosystems, like fertilizer runoff creating oxygen-depleted areas in the ocean, or global shipping routes introducing invasive species into new areas. Because conducting research in the marine environment can be difficult, marine ecosystem processes and population dynamics are poorly understood.  The behavior and lifestyle choices of individual citizen’s significantly impact the health of the marine environment, but the best methods for engaging the public and promoting marine conservation remain illusive. Marine conservation and resource use policy are challenging because marine policy encompasses both the lack of information on marine systems and complex governance issues. Moreover, marine conservation is closely tied with socioeconomic and cultural factors, requiring engagement in such areas with targeted research. Scientific culture itself needs reworking, in that data sharing, collaboration, and funding for fields like taxonomy need to improve. With so many issues facing marine conservation, the questions articulated by Parsons et al. 2014 will help focus the conservation effort.

Past ecological prioritization exercises underemphasized marine issues, so Parsons et al. 2014 highlighted the specific challenges facing marine conservation. Although these questions have not been answered completely, people can, and should, undertake reasonable conservation efforts regarding their subject matter. By serving as a guide for scientific research, these 71 questions, along with evidence-based, participatory, and transparent management, can lead us towards effective marine conservation.


Parsons, E. C. M., Favaro, B., Aguirre, A. A., Bauer, A. L., Blight, L. K., Cigliano, J. A., Coleman, M. A., Côté, I. M., Draheim, M., Fletcher, S., Foley, M. M., Jefferson, R., Jones, M. C., Kelaher, B. P., Lundquist, C. J., McCarthy, J.-B., Nelson, A., Patterson, K., Walsh, L., Wright, A. J. and Sutherland, W. J. (2014), Seventy-One Important Questions for the Conservation of Marine Biodiversity. Conservation Biology, 28: 1206–1214. doi: 10.1111/cobi.12303

The effects of human population density on coral reef fish

By Brittany Bartlett, RJD Intern

Coral reef fisheries are extremely important to the livelihoods of millions of people. Unfortunately, habitat degradation and unsustainable fishing practices have resulted in a decline in these fisheries. Therefore, a recently published article by T.D Brewer et al. entitled “Effects of Human Population Density and Proximity to Markets on Coral Reef Fishes Vulnerable to Extinction by Fishing” seeks to understand the social and economic issues behind this depletion in order to improve management.

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