Aquatics - Introduction

• fish husbandry and biology
• tank set up, fish health, fish feeding
• hardest husbandry field

• Public Aquariums: Aquarist, education or presenting
• Retail work: installing and maintaining aquariums/ponds
• Aquaculture
• Science/Photography
• Marine mammal/photography
• marine education/observer
• rehabilitation 

Most fish:

• vertebrates
• live in water
• breathe primarily with gills
• paired fins
• exothermic

3 Classes:

• Agnatha
• Chondrichthyes
• Osteichthyes

• 30,000 species 
  • e.g. Ocean Sunfish, Atlantic Blue Marlin, Fisher's Seahorse
• Bony skeleton
  • 3 main units: skull, backbone, fin skeleton
• paired fins
• two sets of jaw (oral and pharyngeal)
• scales
  • light, flexible cycloid or chenoid scales
  • mucous layer
    • repels parasites
    • reduce moisture loss
  • some have large protective scales or no scales at all
• 4 pairs of gills covered by operculum (external bone and skin flap)
  • behind head, below cranium
  • lower gill chamber containing bony supports called branchiostegal rays
    • allow fish to open mouth and regulate intake
  • operculum controls outflow
  • respire while stationary
• swim bladder for buoyancy 

• keen senses of vision and hearing
  • used in communication and social interaction
  • helps with shoaling
• eyes on side of head
  • wider field of view
  • rods and cones give good colour vision 
    • bright colouration helps attract mates and defend territory
• produce sounds with swim bladder or by rubbing two parts of the body together

• 1000 species
  • e.g. White Ghost Catshark, Mottled Eagle Ray, Great Hammerhead
• cartilaginous fish
  • strengthened with mineral deposits
  • some = hard, bone-like dorsal spines
• sharks rays and ratfish
• 5-7 pairs of gills with no operculum
• jawed
• paired fins
• dermal denticles
  • also called placoid scales, modified teeth that are covered in hard enamel
    • thousands cover the skin
    • skin has a sandpaper-like texture
    • some rays = thorn-like scales
    • Chimeras lack scales
  • Oily liver
    • cartilage skeletons and fins help buoyancy
    • do not have a swim bladder 

• Ampullae of Lorenzini (system of pores) that detect weak electrical signals
• effective lateral-line systems responds to small vibrations
• sense of smell detects odours even in the weakest solutions 

• internal fertilisation
• male passes sperm into female's cloaca via modified pelvic fin
• females of some species release leathery egg cases
  • young hatch within the body
• other species have a placenta-like structure
  • direct nutritional connection
• no larval stage
  • miniature versions of adults

• 120 species
  • e.g. Broadgilled Hagfish, Dwarf Hagfish
• 'jawless'
  • lampreys have a round sucker-like mouth with rows of teeth made of keratin
  • hagfish have a slit-like mouth with teeth on their tongue
• either pores for gills, either single or separate, or slits
  • hagfish: one to sixteen circular pores
  • lampreys: seven gills 
• no or unpaired fins
• cartilage skeleton 
  • lampreys: few rudimentary vertebrae
  • hagfish: tube-like notochord. Have been classed as invertebrates in the past
• older species = thick bony plates, newer species = slimy skin
• neutral buoyancy 
  • as dense as the water around them

• lampreys have moderately good vision
• hagfish: vestigial eyes but excellent sense of smell to detect carrion and small invertebrates

• lampreys live and breed in freshwater
  • marine species only enter freshwater to spawn
  • swim up rivers to clean gravelly areas, where pairs excavate shallow nests, lay their eggs and then die
  • eggs hatch into ammocoetes larvae that drift downriver to muddy areas where they excavate burrows
  • young feed on filtered microscopic organisms from the water and by suckling detritus