Lecture 3 FISH

Summary: Key Topics in Lecture 3 (Ichthyology)

  1. Shark Behavior and Ecology

    • Sharks exhibit migrations influenced by temperature, prey availability, and predators. Examples include white sharks traveling vast distances and performing vertical migrations for metabolic and feeding advantages.

    • Local shark populations (e.g., basking sharks) have declined due to overfishing, with notable cases like Pachina Bay's breeding colony eradicated by fishing practices.

  2. Spiny Dogfish and Greenland Sharks

    • Spiny dogfish were heavily fished for liver oil (buoyancy aid due to squalene) but are now globally vulnerable.

    • Greenland sharks are long-lived (up to 400 years) with a slow growth rate, inhabiting deep cold waters, and facing minimal predation due to toxic flesh.

  3. Cookiecutter Sharks

    • Small sharks that glow bioluminescently to mimic prey, allowing them to feed on large open-water animals by biting circular plugs of tissue.

  4. Chimaeriformes, Skates, and Rays

    • Characteristics include dorsoventral flattening, fused pectoral fins, and varied reproductive strategies (skates oviparous, rays viviparous).

    • Manta rays are notable plankton feeders, while incidents like Steve Irwin’s death underscore the dangers of their spines.

  5. Lobe-Finned Fishes (Coelacanths)

    • Rediscovered in 1938 after being presumed extinct for 70 million years. They exhibit traits linking fish to tetrapods, such as lobed fins and vertical head movement.

    • Unique features include electrosensors, a fat-filled lung, isosmotic blood, and large eggs. Two distinct species separated by 20–40 million years have been identified.

Flashcards

1. Shark Migrations and Behavior

  • Q: Why do sharks perform vertical migrations?

  • A: For feeding, avoiding predation, and thermoregulation. For example, white sharks descend to cooler depths to slow digestion.

2. Spiny Dogfish

  • Q: Why were spiny dogfish heavily fished globally?

  • A: Their liver oil was a high-demand product for lubricating fine machinery before synthetic replacements.

3. Greenland Sharks

  • Q: What makes Greenland sharks unique?

  • A: They are the longest-lived vertebrates, with lifespans up to 400 years, and inhabit deep, cold waters.

4. Cookiecutter Sharks

  • Q: How do cookiecutter sharks hunt large prey?

  • A: They use bioluminescence to mimic prey, approach stealthily, and remove plugs of tissue from larger animals.

5. Coelacanths

  • Q: Why was the discovery of a live coelacanth in 1938 so significant?

  • A: It was thought extinct for 70 million years, making its discovery akin to finding a living dinosaur.

6. Rays vs. Skates

  • Q: How do rays and skates differ in reproduction?

  • A: Rays are viviparous (give live birth), while skates are oviparous (lay eggs).

7. Manta Rays

  • Q: What is a key ecological role of manta rays?

  • A: They are plankton feeders, crucial to marine food webs.

8. Characteristics of Chimaeriformes

  • Q: What distinguishes chimaeras (ratfish) from sharks?

  • A: They have fused pectoral fins, no anal fin, and specialized ventral gill openings.

Would you like further elaboration on any of these points or additional flashcards?

4o

You said:

what are teh key takeaways

ChatGPT said:

ChatGPT

Key Takeaways from Lecture 3 on Ichthyology:

  1. Shark Behavior and Ecology

    • Sharks demonstrate significant vertical and horizontal migrations influenced by temperature, prey, and predators.

    • Historically misunderstood as stationary, satellite tracking has revealed sharks like great whites and basking sharks travel vast distances, challenging past fisheries management assumptions.

    • Vertical migrations are linked to metabolic efficiency, feeding, and predator avoidance, particularly in ectothermic species like white sharks.

  2. Shark Conservation Concerns

    • Overfishing has led to the decline of many shark species. For example, basking sharks were decimated due to fishing practices and are now nearly extinct in British Columbia waters.

    • The spiny dogfish population collapsed due to the demand for liver oil before synthetic substitutes were developed.

  3. Unique Shark Species

    • Greenland Shark: Lives up to 400 years, grows slowly, and has toxic flesh, which protects it from predators.

    • Cookiecutter Shark: Uses bioluminescent mimicry to lure prey and feed on tissue plugs from larger animals.

  4. Skates and Rays

    • Skates lay eggs in cases ("mermaid’s purses") and are bottom dwellers, while rays are viviparous and often pelagic (e.g., manta rays feeding on plankton).

    • Their dorsoventrally flattened bodies aid in their benthic or pelagic lifestyles, depending on the species.

  5. Coelacanth Rediscovery

    • Coelacanths, once thought extinct for 70 million years, were rediscovered in 1938.

    • They exhibit traits that bridge fish and tetrapods, such as lobed fins, vertical head movement, and a mix of cartilaginous and bony skeletal features.

    • Their discovery highlights the importance of continued exploration and the possibility of uncovering other "living fossils."

  6. Evolutionary Insights

    • Transitional species like Acanthodians (spiny sharks) exhibit features of both cartilaginous and bony fishes, emphasizing the complexity of evolutionary pathways.

    • Coelacanths offer a window into the evolutionary adaptations leading to tetrapods, including electrosensors, fat-filled lungs, and large eggs.