Fish Distribution Patterns

• Divison of Regions: FW and Marine

  • 58% MARINE

  • 41% Fw

• MARINE:

  • Epiplegaic: surface-200m

    • 1.3% of total species

  • Deep pelgaic fishes: 1400 species

    • Mesoplegaic: 200-1000m

    • Bathypelagic: deeper than 1000m

  • Deep Benthic:

    • 6.4% of species

  • Littoral.contential shelf fishes:

    • Inhabit the shore and shelf above 200m

    • 45%

• Freshwater:

  • Higher diversity: 1 species by 15km3 of water

  • Higher likelihood of genetic isolation

  • More energy available to support food webs

  • DIVISION:

    • FW Primary: strictly confined to FW

      • Disbtution not through dispersal

    • Secondary FW: may occasionally enter salt

    • Peripheral FW: spend part of their lifecycle in fresh and salt water

  • Islands with FW species have secondary and peripheral species; primary species could not have bene disbtuuited through dispersal because they are intolerant to salt water

Marine Zoogeographic Regions:

• Indo-West Pacific: most diverse

  • ⅓ of species of shallow marine fishes

• Western Atlantic

• Eastern PAcific

• Eastern Atlantic

• Regions separated by Continents

• Species richness in tropic areas

• Dispersal: Typical pattern of fishes traveling and speciation occurring

  • occurs Across preexisting barriers that are not easily re-crossed

    • Ex: Sheepshead minnow (Cyprinodon vareigatus)

    • Ability to colonize many habitats by dispersing many miles across ocean waters

    • Ability to tolerate wide ranges of salinity

Freshwater Zoogeographic Regions:

• Neartic

• Neotropical

• Afrotropical

• Indo-Malay

• Australian

• Paleartic

  

Non-Dispersal Distributon

• Present distribution= influenced by past arraignments of continents

• Pangea: 430 mya

  • Movement between regions was easier due to the connection

  • Began to break apart 130 mya

• Vicariant Events: tectonic, climatic, or oceanographic occurrences that isolate previously connected populations

  • Ex: continental drift and species of lungfishes

  • Dominant mod, esp in fw fishes

  • S. tritor(spnasih mackerels): sister species to the rest of the mackerel group

    • Located in africa

    • Other makreles are spread globally

    • NA Mackerel: Scomberomorus maculatus

Special Habitats

• Fishes have colonized any ecosystem with some permanence or predictability

• Principle of Convergence: the stronger the selection pressure, the more similar unrelated species will be

• Extreme habitats are colonized to gain comptieitve advantage

• THE DEEP SEA:

  • Occurs in a vertical basis

  • Characteristics:

    • Photophores: light emitting organs

    • Large mouth w/dagger like teeth

    • Enlarged tubular eyes/ or reduced eyes

    • Chin barbels

    • Dorsal fin rays modified as lures

  • Convergent evolution among species

  • Ecological Pressures:

    • Pressure:

      • Fishes made up of incompresible structures = water with dissolved compounds

      • Insensitive to pressure proteins

      • No gas bladder/ adjusted lipid filled gas bladder

        • Rete mirabile: Capillary network involved in gas secretion into the bladder

        • Or Physoclistous

    • Temperature

      • Strong predictor of vertical distribution due to perm. thermocline

      • Only a stressor to fish that move vertically

    • Space: large volume makes it difficult to find food, conspecifics, and mates

      • Sexual dimorphism

      • Ex: Male Anglerfish: dwarfed, sensitive olfactory organs and extensive red muscle, enlarged eyes, high lipid reservers

      • Ex: bristlemouths; smaller males, but are protandrous hermaphrodites

    • Light:

      • Modified eyes that are sensitive to light

      • Biolumnescence: evolved independently in 5 superorders

    • Food: food is scarce-> all marine food chains originate in the euphotic zone

      • Deep sea fishes carnivorous

      • Large mouths to make sure they can take advantage of any feeding opportunity

      • Food attraction by lures and energy conserved as much as possible

      • Mesopelagic fishes: vertical migration to feed at night

• POLAR REGIONS

  • Anatartic Water Temperatures: -2, 2C)

    • Antarctic notothernoids: antifreeze compounds in blood; will not freeze down to -6C

      • Cannot tolerate high temps-> means they are endemic

    • Artici Fishes: fewer endemic species

      • Most are cold tolerant atlantic or pacific species

      • Antifreeze compounds and production

        • Production adjusted by tempes

      • Toleration of temps -2 to 20 C

• ARID

  • Desert fishes

  • Must be tolerant to extreme salinity, alkalinity, temp and depltted OD

  • Withstand flashfloods and droughts

  • Adaptions:

    • Life history with diapause(hiberation) during dry period

      • Diapause is integrated into the lifecycle

      • EX: Cyprinodontiforms, Austrofunduls myseri

        • Eggs are stored for a year in the soil

    • Accessory respiratory structures for using atm O2

    • Estivation: where adults pass the dry season

  • Ex: Clarias catfish

• HIGH ENERGY ZONES

  • Wavy shoes, rapids in rivers, streams, waterfalls

  • Adaptions:

    • Depressed small body; flattened ventral surface

    • Suction device

    • Subterminal or inferior mouth

    • Missing swim bladder

    • Modofiications to respiratory behavior

    • Large, horizontally oriented pectoral fins

    • Ex: Waterfall climbing Sirajo goby

• CAVES:

  • Advantages: little to no compeptiors, predators, and constant moderate climate

  • Disadvanges: no light, infreqnet food

  • Adaptations:

    • Lack of Pigmentation

    • Reduced squamation

    • Loss of light receptors (blind)

    • Expanded lateral line and chemoreceptors

    • Will consume more and build large fat supply when given unlimited food; adaptions to irregular food supply

    • Producer fewer, larger eggs, long parental care, low reproductive rates

    • EX: CRYPTOROA THAMICOLA

      • Waterfall climbing fish

      • Has the adaptions for cave fishes and fishes living in high-energy enviroments