Marine and Freshwater Biogeography, Adaptations, and Ecological Concepts in Fish

FW Biogeographic Provinces

Nearctic, Neotropical, Palearctic, Afrotropical, Oriental, Australian (~15k spp)

Marine Biogeographic Provinces

Indo-Pacific, Eastern/Western Atlantic, Eastern Pacific, Southern Ocean, Arctic (~20k spp)

Ocean Zones

Epipelagic (light), Mesopelagic (dim), Bathypelagic (dark, cold, high pressure), Abyssal, Hadal

Species Composition Change

Species shift from visual predators to bioluminescent, low-metabolism fishes

Adaptations to Deep Sea

Pressure-resistant enzymes, camouflage, slow growth

Lessepsian Migrants

Red Sea species entering Mediterranean through Suez Canal since 1869; now 400+ species

Vicariance

Species separation by barrier; Example: Isthmus of Panama (3 Ma) splitting Atlantic/Pacific fish lineages

Deep-Sea Organism Factors

Pressure, cold, darkness, low food — adaptations include antifreeze proteins, bioluminescence, large mouths, slow metabolisms

Marine Snow

Falling organic particles feeding deep-sea communities

Endemics in Antarctica vs Arctic

Antarctica is isolated, stable, cold; Arctic connected to other oceans → fewer endemics

Notothenioid Fishes Adaptations

Antifreeze glycoproteins; lipid buoyancy replacing swim bladder

Neutral Buoyancy Impact

Neutral buoyancy → access to new niches

Desert Living Challenges

High heat, evaporation, salinity swings — adaptations: aestivation, salinity tolerance, burrowing eggs

Messinian Salinity Crisis

5.9-5.3 Ma; Mediterranean nearly dried; massive salt deposits + faunal turnover

Diurnal Vertical Migration (DVM)

Diel vertical migration: mesopelagics rise at night; significance: energy transport + predator avoidance

Biofluorescence vs Bioluminescence

Biofluorescence: re‑emits light (catsharks); Bioluminescence: produces light via chemistry (lanternfish)

Factors Affecting Species Distribution

Plate tectonics, climate oscillations, life-history traits, habitat needs

Predator-Prey Arms Race

Continuous coevolution; stopping → extinction risk

Types of Pursuing

Chase pursuit (tuna) vs lie-in-wait (pike); Deceptive pursuit = lures (anglerfish)

Fish Tactics to Avoid Predators

Countershading, transparency, mimicry, burying

Advantages and Disadvantages of Schooling

Not provided in the note

Advantages of schooling

dilution, confusion, feeding.

Disadvantages of schooling

disease, visibility.

Aggressive mimicry example

fangblenny.

Protective mimicry example

juvenile drum mimicking toxic species.

Convergence in lie-in-wait predators

share elongate bodies + camo.

Open ocean fish body type

fusiform.

Deep sea fish body type

red/black with large mouths.

Fish communication senses

Visual, chemical, acoustic, electrical signals.

Types of symbiosis

Mutualism (+/+), commensalism (+/0), parasitism (+/-).

Daily activity types in fishes

Diurnal (day), crepuscular (twilight), nocturnal (night).

Daytime reef shoals activity

diurnal planktivores (chromis, fusiliers).

Semilunar periodicity

Spawning aligned with new/full moons; grunion spawn at highest tides.

Intertidal spawner example

Capelin.

Semilunar reef spawner example

surgeonfish.

Migration example in fishes

salmon.

Navigational systems used by salmon

geomagnetic maps, olfaction, sun.

Photo-, geo-, and rheotaxis

Photo = light; geo = gravity; rheo = current.

Diadromous fish example

salmon.

Oceanodromous fish example

tuna.

Potamodromous fish example

trout.

Navigation in fourline cardinal fish

Uses sun compass, reef soundscape, and olfactory cues.

Population vs metapopulation

Population = one species group; metapopulation = linked pops.

Assemblage definition

multi-species set.

Keystone species example

Sea otters; removal → urchin boom → kelp collapse.

Major causes of fish depletion

Overfishing, habitat loss, pollution, climate change, invasives.

Types of habitat loss

Destruction (reef blasting), degradation (pollution), fragmentation (dams).

Introduced species definition

Non-native species.

Vectors for introduced species

ballast water, aquarium trade, aquaculture, canals.

Example of introduced species in Florida

lionfish via aquarium release.

Fishing down the food web

Shift from large predators → small species.

Clean fishery example

pole-and-line tuna.

Dirtiest fishery example

bottom trawling.

Faunal homogenization definition

Regions become more similar due to invasions/extinctions.

Extinct/endangered fishes habitat

FW habitats small + impacted by dams/pollution.

6th mass extinction definition

Current human-driven extinction; 100-1000× background.

IUCN Red List purpose

IUCN assesses extinction risk globally.

Freshwater habitats percentage

Freshwater habitats make up <1% of Earth's water but contain ~40% of fish species.

Factors responsible for freshwater species pattern

High geographic isolation of freshwater systems promotes allopatric speciation; Environmental variability and heterogeneous habitats drive rapid adaptation and niche diversification.