Lecture 1 - Fish Habitats Flashcards
What is a fish?
Poikilothermic, aquatic chordate with appendages (when present) developed as fins, whose chief respiratory organs are gills and whose bodies are usually covered with scales.
Definition of a fish:
________ aquatic ______ with appendages (when present) developed as _____, whose chief respiratory organs are _____ and whose bodies are usually covered with ______.
Poikilothermic Chordate Fins Gills Scales
What does poikilothermic mean?
Internal temperature regulated by the environment.
What are the two reasons that fish are not cold blooded?
1 - Fish in warm water have warm blood
2 - Some fish (e.g. tuna) can increased their body temperature above ambient using different sorts of muscles to heat blood up
A chordate is any animal with ____ ____ at some point in development; a dorsal _______ _____ cord; a _______ at some point in development, and a _____-_____ tail.
gill slits
hollow nerve
notochord
post-anal
All _______ are _______ but not all ________ are ________.
Chordates or vertebrates
All vertebrates are chordates.
Not all chordates are vertebrates.
What are the ecological factors that fish have to worry about?
Food, predation, invasive species, spawning habitats.
What are the environmental parameters fish have to worry about?
Salinity, how much water is present, temperature, light intensity, pH, depth, DO
What drives species diversity locally?
Temperature, depth (to some extent), light intensity - diel cycling, turbidity levels
Variation in turbidity levels can vary due to natural and anthropogenic factors. Explain.
Natural - some fish prefer murky waters and some prefer clear waters
Anthropogenic - stirring up sediment
Sturgeon are a massive, long-lived local fish. They were though to be locally extinct but, have a made a resurgence locally. Explain and indicate which is the most important factor.
1 - Dr. Pitcher started revamping spawning habitats
2 - Decreased turbidity (most important.
3 - Increased quality of environmental parameters
What are the outer ranges of salinity in which fish can survive.
0 - 140 ppt
At 140 ppt, what occurs?
Salt crystallizes out of solution
Why does depth matter? i.e. what factors are related to depth?
1 - Light (the deeper you go, the less light there is)
2 - Temperature (Deeper water will generally be colder’ up to a certain point)
3 - Pressure - increases linearly with depth (1atm/10m)
Describe the temperature ranges in which fish can be observed.
-2°C to 40°c
What are the issues at the upper range of the temperature spectra? The lower range?
High temps. - cellular degradation and denaturation of proteins
Low temps - freezing
Most fish do better at ____ temperatures than _____ temperatures.
high
low
There is roughly ____ distribution of fish species between marine and freshwater systems, however there are more in ______ environments compared to _________.
even
marine
freshwater
Why are there more marine fish than freshwater fish?
1 - Fish evolved in marine environments and then moved to freshwater
2 - There is more seawater than there is fresh
Why is there so little freshwater?
Much of the freshwater is unavailable under the form of glaciers
What drives species diversification in freshwater?
These are highly productive environments.
Why are freshwater environments highly productive?
Lots of nutrient input from land
_________ drives species diversification. (Related to food)
Productivity
What areas are productive in strictly marine environments?
Coastal zones
What is an estuary? What type of water is located there?
What are they important for?
Estuaries are a combination of both fresh and saltwater and are the locations where freshwater meets the ocean.
They are composed of brackish water, i.e. are within 0-32 ppt (32 being open ocean and 0 being freshwater)
Estuaries are important nursery grounds for marine fish.
Define a lotic environment.
High flowing environment with lots of water flow. River or stream.
Define a lentic environment.
Low flowing environment. Characteristics of a lake.
Why do we care about flow?
It can drive species diversification since flow affects morphology.
In a higher flow environment, the fish needs to be more hydrodynamic.
In a lake system, the fish can be more blobbed shaped.
What are the different oceanic habitats (related to depth)?
Pelagic -epipelagic -mesopelagic -bathypelagic --Abyssal Benthic/Benthal
What does pelagic mean?
Generally refers to the open water. i.e. the top and not the bottom
What does benthic mean? Benthal?
Fish associated with the bottom.
Officially, benthic means the bottom and benthal means near the bottom.
In the ocean, the pelagic zone is split into three zones. These are?
Epipelagic, mesopelagic, bathypelagic
Describe the epipelagic zone.
- Top layer, ranging from 0-200m in depth.
- Most oceanic fish are found here
- lots of biomass
- photosynthesis is higher than respiration
- also called the euphoric zone - means that light is not limiting during the day
Describe the mesopelagic zone
- Roughly from 200m-1000m in depth
- Light is available throughout most, if not all, of the water column
- light attenuates as depth increases
- vision can still be used here
- photosynthesis is less than respiration
- reduction in biomass with depth
- permanent thermocline
As we go deeper in the mesopelagic what occurs? What adaptations has this caused?
3 things:
1 - Reduction in light
–>fish will have larger and larger eyes. Adaptation allowing for more sensitive vision to catch every photon of light
2 - Reduction in biomass
–> fish have to be more efficient at hunting
–> mechanisms to reduce metabolic demand
3 - Permanent thermocline
–> deeper is colder
–> species will choose where to live in water column based on preferred temperature
What is a reason that there is a permanent thermocline in the mesopelagic?
Too deep for surface mixing
Describe the bathypelagic zone.
- Anything below 1000m
- no sunlight
- reduction in eyes
- sensory adaptations to take over loss of eyesight
- always cold, no thermocline
- no seasonal cycling in temperature
What are the issues bathypelagic fish face?
Cold, dark, poor amount of food, hard to find mates
What is the term used for really deep living fish? What zone is it part of?
Abyssal, part of the bathypelagic
Describe the abyssal zone
- Below 4000m
- fish live in open gashes on the sea floor
What is the deepest fish have been observed?
8300m
