Sharkpedia

Did you know that shark body form can change as they grow? Why does that happen? Why does it matter? Find out this week on our episode investigating these questions of bull sharks with Joel Gayford!

Title: Ontogenetic Shifts in body form in the bull shark Carcharhinus leucas

Summary: It is believed that body growth is strongly correlated to trophic and spatial ecology through ontogeny, or as a shark ages. Gayford et al. used bull sharks as their study species to better understand morphological growth at many different locations along a shark's body. They found shifts in functional demands across the body through ontogeny, seemingly driven by selective pressures relating to trophic and spatial ecology. They also found significant differences in scaling trends between life stages and sexes. They ultimately discuss the implications of their results for existing ecomorphological hypotheses and provide a robust study to add to much needed research in this area.

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Juvenile shark presence in an area does NOT mean that that area is a shark pupping or nursery ground. So how do we know what actually makes a shark nursery ground? What even IS a nursery ground? Is it different than a pupping ground? Why does any of this matter? Find out this week with our special guest, Dr. Michelle Heupel!

Dr. Heupel joins us to talk about her article, "Shark nursery areas: concepts, definition, characterization and assumptions" (Heupel et al. 2007).

Article Summary:

Shark nursery habitats are critical areas that sharks rely on for their early life stages. However, the criteria defining shark nursery grounds has been inconsistent through history. These inconsistencies can make management strategies more difficult, as some definitions could imply that all coastal areas are nursery habitats, and other definitions are insufficient. In this study, Heupel et al. propose a new definition for shark nursery habitats that will more accurately pinpoint Essential Fish Habitat. That definition is: (1) sharks are more commonly encountered in the area than other areas; (2) sharks have a tendency to remain or return for extended periods; and (3) the area or habitat is repeatedly used across years. These criteria make the definition of shark nursery areas more compatible with those for other aquatic species. The improved definition of this concept will provide more valuable information for fisheries managers and shark biologists.

You can follow Dr. Heupel @michelleheupel on instagram, and follow her work on Research Gate and Google Scholar!

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This week we had a very fun time talking with Dr. Taylor Chapple about maximizing datasets with video biologgers that are attached to sharks! Are you listening to the podcast and wondering who Dr. Alex McInturf is? Listen to our very first interview episode in Season 1!

We chat with Dr. Chapple about his article, Ancillary data from animal-borne cameras as an ecological survey tool for marine communities

Article Summary: Underwater visual surveys, such as diver-based video surveys, are a common and essential technique in measuring and managing marine ecosystems. However, there are several limitations to doing such surveys, such as recreational diving depth limitations, or animal interactions that preclude safe diving (such as White shark - sea lion interactions). Biologging camera tag devices are commonly used to study a single, focal species' behavior. However, ecosystem-wide data is collected and could be used to monitor and assess habitats that may not be accessible to humans. In this study, Chapple et al. use a video camera logger on a White shark off Gansbaai, South Africa, and a Grey Reef shark within the Chagos Archipelago, to determine if video logging could be used to measure the habitat structure of their respective environments. They used established methods to analyze video data and found that the biologging from the sharks was relatively comparable. Using biologgers such as the ones used in this study could maximize the overall cost and effort of tagging deployments by gathering more ecosystem-wide data, than just the focal species data.

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This week we talk with Dr. Haley Dolton about how she studied the physiology of basking sharks in Ireland! This is no small feat.

We read Dr. Dolton's article, "Regional endothermic traits in planktivorous basking sharks Cetohinus maximus"

Article Summary: The majority of sharks are classified as cold-blooded or ectotherms. Sharks are constantly battling heat loss to the surrounding water. To combat this, some fast-swimming apex species are classified as regional endotherms, having uncommon physiological traits such as elevated internal body temperatures, centralized red muscle, and thick-walled hearts. Within the order Lamniformes, housing the only regionally endothermic sharks, you can find the basking shark which is a large, filter-feeding planktivorous species. Previous research has led to the conclusion that basking sharks are ectothermic. To investigate this, Dolton et al. collected muscle samples and measured the internal temperature of basking sharks finding that they displayed the traits previously stated. Their research leads to the finding that basking sharks may not be correctly classified as an ectotherm, which is a surprising find!

You can follow Dr. Dolton @HaleyDolton on Instagram and Twitter!

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From the Vault - This episode was recorded with Dr. Brit Finucci back in 2022! But.... life happens. We are so excited to finally share this episode with our sharkies! Join us this week to hear about Dr. Finucci's work studying deep sea sharks and their associations with each other! How do you even research deep sea sharks? How many species are there? How do sharks glow in the dark? Find out this and more!

The article we are reviewing with Dr. Finucci is titled, "Aggregations and associations in deep-sea chondrichthyans"

Summary (modified abstract): Group living has been recorded across a diverse range of chondrichthyans, but given the nature of deep sea chondrichthyans, any inferences of social associations have yet to be described. Using a companion preference analysis, aggregating behaviour and associations in deep-sea chondrichthyans (four holocephalans, ten elasmobranchs) were evaluated across class and group size from long-term archived fisheries independent research trawl survey datasets. Results indicated that not all selected species engaged in aggregative behaviour, but those that did suggested patterns of sex- and size-specific associations, which varied with catch density. Adult females were caught most frequently in low densities, and were highly associated with other adult females. Adult males were consistently associated with each other. The nature of associations provides important insight for selective mortality, such as aggregation-targeting fisheries. 

You can follow Dr. Brit Finucci's work on twitter @BritFinucci

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This week we are joined by Dr. Julia Mason to talk about fishers ecological knowledge of Smooth Hammerhead sharks in Peru! Why is it important to incorporate fishers into management decisions? Why aren't they always included in the management discussion of species they target? Find out this and more!

We read Dr. Julia Mason's article, Fishers' solutions for hammerhead shark conservation in Peru

Article Summary: Shark populations have been declining worldwide, with heavy implications for the health of our oceans. The increase in regulations put forth by both national and international entities to protect declining shark populations has had limited effectiveness with a major challenge in policymaking coming from a lack of data for small-scale fisheries. In Peru, sharks are mostly caught through small-scale fisheries and are targeted for human consumption rather than strictly for fins. In 2016, Peru implemented a seasonal ban on hammerhead fishing from January to March of each year in an attempt to restrain fishing pressure. However, this seasonal ban does not protect breeding females, which are present in September-December. Smooth hammerheads were the 3rd most caught shark in Peru before this ban, behind the blue shark and shortfin mako. This article aims to better understand fisher perspectives on this ban as well as record their solutions. Mason et al. interviewed boat owners and captains in 3 major Peruvian ports, San Jose, Mancora, and Salaverry. They found that the majority of fishers welcome conservation measures with a smaller percentage objecting, largely due to a lack of transparency and fisher participation in the ban development and implementation process. Additionally, fishers reveal gaps in the ban's effectiveness based on the movement behavior of hammerhead sharks. 

You can follow Dr. Julia Mason @JuliaGMason

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Happy New Year Sharkies! Join us as we talk about why we took such a long hiatus, our favorite shark experiences of 2023, and what's to come for Sharkpedia in 2024.

This week we are joined by Dr. Ana Martins, a postdoctoral researcher at Dalhousie University studying the shark meat trade. The shark fin and meat trade is a common media topic but angler knowledge and opinions seem to be rarely incorporated into these discussions. In her home country of Brazil, Dr. Martins utilized angler knowledge to uncover trends in the shark meat trade. Listen through the episode until the end for a rather fishy field story which will have you laughing in your seat. 

The article which is the base of our discussion this week is, "Analysis of the supply chain and conservations status of sharks (Elasmobranchii: Superorder Selachimopha) based on fisher knowledge"

Article Summary:

Increasing fishing effort has caused declines in shark populations worldwide. Understanding biological and ecological characteristics of sharks is essential to effectively implement management measures, but to fully understand drivers of fishing pressure social factors must be considered through multidisciplinary and integrated approaches. Martins et al. aimed to use fisher and trader knowledge to describe the shark catch and product supply chain in Northeastern Brazil, and evaluate perceptions regarding the regional conservation status of shark species. They had 3 main objectives: identify the presence of a supply chain of two shark products (meat and fins), (2) describe the supply chain for each product, and (3) qualitatively evaluate fisher and trader perceptions regarding the regional conservation status of shark species. Several threatened shark species were reportedly often captured off shore and traded at local markets. This reported and observed harvest breaches current Brazilian environmental laws. Fishing communities are aware of population declines of several shark species, but rarely take action to avoid capture of sharks. The continuing capture of sharks is mainly due to a lack of knowledge of environmental laws, lack of enforcement by responsible authorities, and difficulties encountered by fishers in finding alternative income streams. National and regional conservation measures are immediately required to reduce overfishing on shark populations in Northeastern Brazil. Social and economic improvements for poor fishing communities must also be implemented to achieve sustainable fisheries.

Follow Dr. Ana Martins on Twitter @martins_apb

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