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Question 1

Whale communication in a pristine environment can exceed 10,000km. In the presence of anthropogenic noise e.g. intense shipping (where the noise frequency overlaps the whale calls – masking effect) whales can react by:

Answer 1

• Increase or decrease the frequency used
• Call louder
• Wait for silence

Question 2

What part of sound are marine mammals sensitive to?

Answer 2

The sound can be measured as a change in pressure within the
medium, which acts in all directions, described as the sound pressure. The unit for pressure is Pascal (Newton/m2).

Each sound wave has both a pressure component (in Pascal) and a particle motion component, indicating the displacement (nm), the velocity (m s-1) or the acceleration (m s-2)
of the molecules in the sound wave (Nedelec et al. 2016).

Depending on their receptor mechanisms, marine life is
sensitive to either pressure or particle motion or both.

Question 3

Porpoise clicks are highly stereotypical sonar signals. They are unique in being

Answer 3

Porpoise clicks are highly stereotypical sonar signals. They are unique in being very short (50–150 µs) and containing virtually no energy below
100 kHz. Main part of the energy is in a narrow band 120–150 kHz, which makes the signals ideal for automatic detection.

Question 4

What different sounds do mysticetes make?

Answer 4

Moans
-Range from 1-30 sec, low frequency (20-200 Hz)
-Ideal for long range communication
Thumps/knocks
-Low Frequency (under 200 Hz)
-Thought to be used for social organization
Chirps/Whistles
-Above 1 kHz, can change frequency rapidly and are very short
-Social sounds
-May be used during feeding events/individual recognition
Mysticete Song
30 – 8000 Hz
-Supposedly only males sing
-Usually sung during the breeding season
-Could advertise male’s fitness and control spacing
-Changes over time

Question 5

What sounds do pinnipeds make?

Answer 5

Pinnipeds:
Broad Range of acoustic signals both in air and under water
Mostly within the range of human hearing (200 to 2000 Hz)
Grunts, rasps, rattles, growls, trills, clicks, and whistles

Question 6

What sounds do sirenians make?

Answer 6

Sirenians:
Usually, low frequency ranging from 1 – 8 kHz and low in amplitude
Described as chirps, whistles, barks, and trills

Question 7

Marine mammal k /r strategist

Answer 7

K‐strategy species differ from r‐strategy species in that they maximize lifetime reproductive success by having a low reproductive potential but high survivorship.

With their large adult body size, high lifetime expectancy, small litter size and delayed reproduction, marine mammals are typical K‐strategists.

Question 8

HOw do mysticetes and odontocetes differ in breeding?

Answer 8

Most odontocetes can be considered income breeders, because they continue to feed throughout the reproductive cycle.

In contrast, mysticetes can be considered capital breeders because they support the costs of reproduction on low‐latitude breeding grounds with stored energy acquired on high‐latitude feeding grounds.

Question 9

What are the different terms for different mating strategies?

Answer 9

Promiscuous - both sexes with multiple partners (most cetacean species)

Polygynous - males with multiple mates (many pinniped species males have harems, northern fur seal males can have 100+ females)

Polyandry - females with multiple mates (cetaceans)

Monogamy - mating pair remains together over time (not in marine mammals)

Question 10

What are the different methods of age determination?

Answer 10

• Age needed to estimate lifehistory parameters
• Reading decalcified, sectioned and stained teeth (method by Reimers och Nordby 1968)
• Growth Layer Groups (GLGs)
• Complete GLG = one year
• The Corpus luteum (CL) is a temporary endocrine gland in the ovary and is characterised by a distension of the ovarian surface, often orange-yellow in colour inside.
• he CL degenerates and gradually transforms into a whitish fibrous scar tissue, the Corpus albicans (CA), which will remain but reduce in size over time.

Question 11

How do cetaceans swim?

Answer 11

The tail flukes are moved upwards by contracting the longissimus dorsi and epaxial muscles and relaxing the hypaxial muscles and downwards by reversed contraction and relaxing of these muscles.

Question 12

hair layers pinnipeds

Answer 12

Sea otters and the polar bear has only fur. Two layers: outer protective guard hairs and inner soft underfur hairs.
Fur seals also has two layers of fur and in addition a thin-moderate blubber layer .
Sea lions, phocid seals and walrus lack underfur and have a combination of fur and blubber, rely on blubber for insulation in water.
All phocid seals, the sea otter, and the beluga whale undergo an annual molt.

Question 13

What types of mechanoreception do cetaceans have?

Answer 13

Cetaceans: mainly the skin
– Whales: ~100 thin sensory hairs around jaws
– Dolphins: 2-­10 follicles around jaws
– River dolphins: immobile thin bristles around jaws

Otters: Sensitive front paws, vibrissae

Manatees: sensory hairs
– All over body, highly specialized around mouth

Pinnipeds: specialized vibrissae

Question 14

What is the functions of Whiskers (vibrissae)?

Answer 14

Functions:
Sound: The Baltic ringed seal can sense water-borne sound waves with their vibrissae to guide their way in the dark and often cloudy waters beneath the ice
In addition, the vibrissae may sense changes in swimming speed and direction,which could be important while navigating in darkness.
Evidence of the heat conduction of vibrissae of harbor seals suggests that they also play a thermoregulatory role in maintaining high sensitivity in low ambient temperatures.
The possible use of vibrissae in prey detection also has been investigated.

Question 15

Give some cetacean distribution patterns.

Answer 15

Distribution can be identified as cosmopolitan (inhabiting most or all of the world’s oceans e.g. killer whale) and disjunct (separated by a barrier e.g. harbour porpoise in the Atlantic, the Pacific and the Black Sea) or more or less widespread but limited to a particular area and have either endemic (only found a particular area e.g. Vaquita porpoise) or circumpolar distributions (e.g. restricted to Antarctic or Arctic waters e.g. beluga whale).

Antitropical distribution: The equator acts as a ”barrier” with different populations of a species (e.g. northern and southern elephant seal) or a species pair of the same genus (e.g. Vaquita (Phocoena sinus) and Burmeister’s (P. Spinnipinnis) porpoise) in eastern Pacific.

A barrier could be e.g. a land mass, ocean basin, dam, underwater ridge that have changed through time and separated a species in different geographical regions (e.g. dams and river dolphins).

Question 16

Visual strip/plot vs line transect

Answer 16

Strip transect - one or more observers survey along a line, counting all objects within a pre-determined distance of the line (e.g. 200m on each side).
A fundamental assumption of these methods is that all objects within the strip are counted. This assumption is difficult to meet for many populations, and cannot be tested using the survey data.
Distance sampling (Line transect) - one or more observers move along a line, counting all objects and record distance and angle to the objects from the survey line.
Relaxed assumption: still need to estimate the proprtion of missed animals g(0) on the actual transect line.

Question 17

pros and cons of capture-recapture

Answer 17

Capture–recapture methods where individual animals are marked are applicable to some species that are not amenable to distance sampling methods, and can yield estimates of survival and recruitment rates, which distance sampling cannot do.

Capture–recapture can be efficient for populations that aggregate at some location each year, whereas distance sampling methods are more effective on dispersed populations.

Capture-recapture also allow to estimate survival, association patterns etc.

Question 18

what are the assumptions of capture recapture?

Answer 18

First, a sample of individuals is captured, marked and released (n1),

then a second sample of individuals is captured (n2) of which a number are already marked (m2),

the proportion of individuals that are marked in the second sample can be equated with the proportion in the population at large (N).

Assumptions? No births, deaths, immigration or emigration between sampling events, sampling does not affect future sampling, marks are unique and not lost or gained, all animals have equal capture probabilities.

Question 19

What are the different types of pectoral fin in batoids?

Answer 19

Pectoral fins
Undulatory-drag based
Pass waves down fins (ant to post)

Oscillatory- lift based
Flap fins up and down

Axial-undulatory-lift based
Undulate pec fins, but also pass waves down axial skeleton (ant to post)

Question 20

What are the different types of tail?

Answer 20

The tail can be heterocercal, which means that the vertebrae extend into a larger lobe (A below) of the tail or that the tail is asymmetrical. Most fish have a homocercal tail, where the vertebrae do not extend into a lobe (C below) and the fin is more or less symmetrical expressed in a variety of shapes.

Epicercal means that the upper lobe is longer (as in sharks), hypocercal means that the lower lobe is longer (as in flying fish)

Question 21

Describe the uses of a spiracle.

Answer 21

The spiracle is a basically a first gill slit. It appears as an opening behind the eye. It is used to provide oxygenated blood directly to the eye and brain through a separate blood vessel, and/or to pump water over the gills.

It is absent in many sharks, e.g. fast swimming sharks and is larger in bottom dwelling sharks. In rays, the spiracle is larger and more developed and is used to actively pump water over the gills to allow the ray to breathe while buried in the sand.

Question 22

Senses: Ampullae
of

Answer 22

The ampullae of Lorenzini* are small vesicles and pores (electroreceptores) that form part of an extensive subcutaneous sensory network system.

They are found around the head and appear as dark spots (photo of a porbeagle shark head). Each ampullae contain multiple nerve fibres that are enclosed in a gel-filled tubule (glycoprotein with electrical properties) which has a direct opening to the surface through a pore.

The ampullae detect weak magnetic fields produced by other fishes.

This allows the shark to locate e.g. prey that buried in the sand. Sharks may also use the ampullae to navigate to the electric fields of ocean currents and earth’s magnetic fields.

Question 23

What does the lateral line consists of?

Answer 23

t consists of structures called neuromasts which are located in canals that lie just below the surface of the skin or the scales. Similar to the ampullae of Lorenzini there are pores that open to the outside and movement caused by prey can be detected by the neuromasts.

Question 24

Sharks have the basic eye structure found in all vertebrates, but with some modification.

Answer 24

The shark eye has a reflecting layer called a tapetum lucidum located behind the retina (the light-sensitive tissue lining the inner surface of the eye).

The structure consists of a layer of plate-like cells filled with silver guanine crystals. The crystals reflect light that has already passed through the retina and redirects it back to restimulate the retina as it passes out through the eye. This boosts the visual signal, especially in low light levels giving sharks high visual acuity (sharpness).

Question 25

Most sharks are “cold-blooded“- their internal body temperature matches that of their ambient environment.

what sharks differ form this?

Answer 25

Members of the family Lamnidae, such as the shortfin mako shark and the great white shark, are homeothermic and maintain a higher body temperature than the surrounding water. In these sharks, a strip of aerobic red muscle located near the center of the body generates the heat, which the body retains via a countercurrent exchange mechanism by a system of blood vessels called the rete mirabile.

Question 26

The blood and other tissue of sharks and Chondrichthyes in general are isotonic (same or similar salt concentration) to their marine environments because of the high concentration of urea and trimethylamine N-oxide (TMAO), allowing them to be in osmotic balance with the seawater. This adaptation prevents most sharks from surviving in fresh water.

what shark is an exception?

Answer 26

Bull shark is an exception which has developed a way to change its kidney function to excrete large amounts of urea and allow it to move far up in rivers.

Question 27

In a typical ectothermic fish blood returns from the body to the heart and then travels to the gills for gas exchange
Heat escapes so that oxygenated blood returning from the gills is the same temperature as the ambient water
In large scombroids the cool blood does not pass down the dorsal aorta but is diverted to large peripheral vessels that run along the outside of the body

gove an example of this

Answer 27

‘Countercurrent’ flow
retia mirabilia (“wonderful net”)
measurements on Albacore tuna indicate a heat transfer efficiency of ~98%!
Similar structures seen elsewhere to maintain elevated brain and gut temperatures

Question 28

Why the hammer?

Answer 28

(in hammerhead sharks)? There are two basic thoughts:
Hydrodynamic advantages (head is flattened on the lower surface and rounded on the upper and may therefore increase lift)

Sensory enhancement. The nostrils of most species are located near the tips of the hammer and have specialised grooves which channel scent-bearing water to the nostrils. By having their nostrils mounted far apart they can sample the water column in stereo. The Lorenzini ampullae are distributed over the entire undersurface of the hammer, and the width of the head may work as a “metal prey detector”.

Question 29

What happens to the ecosystem when and if you remove large-scale apex predators?

Answer 29

Lack of prey regulation – instabillity in the system

Ecosystem shift

Possible cascading effects

Lower productivity in the ecosystem

Loss of important indicator species on the health of the marine system

Question 30

Despite the basic approach to swimming described, fishes occur in a wide variety of body shapes so there is considerable variation in how they swim
It is possible to divide these locomotory types into four basic types:

Answer 30

1. ANGUILLIFORM
2. CARANGIFORM (SUBCARANGIFORM)
3. OSTRACIFORM
4. SWIMMING WITH THE FINS

The types are characterised by how much of and which body parts are involved in propulsion
Whether body or fins UNDULATE or OSCILLATE
UNDULATION – sinusoidal wave passing down body or fins
OSCILLATION – structure moving/beating back and forth

Question 31

Anguilliform

Answer 31

Involves sinusoidal undulations
Seen in most eels, dogfishes and many fish larvae
Occurs in fishes with very flexible bodies
All but the head contributes to the propulsive force
The wave increases in amplitude as it moves along the body

Question 32

Carangiform (subcarangiform)

Answer 32

To avoid ‘self-braking’ faster swimmers involve only the posterior segments of the body in wave generation
Use ligaments to transfer force from muscles to caudal region
More advances fishes have increasing use of tail and decreasing use of anterior body

Question 33

Ostraciform

Answer 33

Observed in boxfishes (Family Ostraciidae) and some other Tetraodontiformes (cowfish, trunkfish) is extreme in that only the tail oscillates while the body is held rigid
Contract the entire muscle mass on one side of the body then the other – produces a sculling motion
These fishes rely on armour rather than speed for protection from predators

The caudal fin is small and not differentiated into distinct lobes - ISOCERCAL

Question 34

swimming with fins

Answer 34

Different types in this group – all employ median and paired fins rather than body-tail couplings
Tetraodontiforms (triggerfish, sunfish) flap their dorsal and anal fins synchronously
Narrow fins act as wings and generate lift (forward thrust) continuously

Amiiform swimmers (seahorses, pipefishes, bowfins) the undulations pass along the dorsal fin
Frequency of wave progression can be very high; 70Hz in some seahorses
Labriform swimmers (wrasses, parrotfishes) row their pectoral fins, pushing with the broad blade then feathering it in the recovery phase
Negative lift during recover phase - ‘bouncing’ appearance

Question 35

The muscles of fish are layered rather than bundled as in the other vertebrates
Each segment, or sheet, of muscles is called a

Answer 35

Each segment, or sheet, of muscles is called a myomere or myotome and is separated from its neighbour by a sheet of connective tissue called a myosepta

Question 36

Pressure/lift-induced drag
As tip vortices depend on fluid circulation the stronger the circulation the greater the Dv incurred
Fishes can reduce this in two ways (much the same as aeroplanes)

Answer 36

Double the foil span
The same lift/thrust can be generated by weak circulation over a long span, doubling the span halves Dv
Can see this in the long, thin caudal fins of fast-swimming fishes; the aspect ratio (AR) of tuna fins is much higher than those of salmonids

2) For a given AR, Dv will be minimal if spanwise lift distribution is elliptical
All fishes that cruise at high speeds have crescentic, elliptical caudal (thrust) and pectoral (lift) fins
These fins are not suitable for rapid acceleration or agile manoeuvring
Salmonids will have much broader, low AR fins

Question 37

Reducing Skin friction drag
As Dsf is nearly always more important than Dv fishes require mechanisms to reduce skin friction drag

Answer 37

1) Reduce wetted area (A)
Fast-swimming scombroids have fins that retract into slots when not required for manoeuvring; fins are often discontinuous or scooped out at the rear
2) Reduce lateral movements – e.g. by using lateral keels
3) Boundary layer (BL) control
Larger fishes experience turbulent BL need to delay transition from laminar to turbulent BL. Scales facilitate this and some fish also has a slimy layer

Question 38

The main sense unit of the lateral line is the

Answer 38

• The main sense unit of the lateral line is the neuromast.
• The neuromast is a mechanoreceptive organ which allows the sensing of mechanical changes in water.
• The neuromasts located along the lateral lines in subdermal, fluid filled canals.
• Each neuromast consists of receptive hair cells whose tips are covered by a flexible and jellylike cupula.

Question 39

Courtship - colour, size, and behaviour important

Secondary sexual characteristics (4)

Answer 39

Secondary sexual characteristics

1. Monomorphic (males and females alike)
2. Permanently dimorphic (mature sexes distinguishable)
3. Seasonally dimorphic (mature sexes distinguishable only at spawning time)
4. Polymorphic (different individual colours have higher reproductive success in different habitats)

Question 40

What are the different types of spawners?

Answer 40

• Open substrate spawners - scatter their eggs in the environment. They usually spawn in shoals without complex courtship rituals, and males outnumber females
• Broadcast spawners - release their gametes (sperm and eggs) into open water for external fertilisation. There is no subsequent parental care. Produce very large numbers of eggs but experience very high mortality – 2 to 10% per day
  
  • Pelagic spawners: a type of broadcast spawners, spawn in the open sea, mostly near the surface.
  • Benthic spawners: deposit their spawn on or near the bottom of the sea (or lake). They are usually demersal fish such flatfish.

Question 41

What are the different types of egg layers?

Answer 41

Egg scatterers: scatter adhesive or non-adhesive eggs to fall to the substrate, into plants, or float to the surface. These species do not look after their brood and even eat their own eggs.

Egg depositers: deposit eggs on a substrate (rocks, plants). Egg depositors usually lay fewer but larger eggs than egg-scatterers. Egg depositors fall into two groups: those that care for their eggs, and those that do not.

Brood hiders hide their eggs but do not give parental care after they have hidden them. Brood hiders are mostly benthic spawners that bury the fertilized eggs (e.g. some salmon species)

Guarders protect their eggs and offspring after spawning by practicing parental care (also called brood care). Increases offspring chance of surviving (and hence reproductive success).

Parental care can take a variety of forms: guarding, nest building, fanning, splashing, removal of dead eggs, retrieval of straying fry, external egg carrying, egg burying, moving eggs or young, ectodermal feeding, oral brooding, internal gestation, brood-pouch egg carrying.

Cavity spawners: lay eggs in a cave or cavity. These fish form pairs and have advanced brood care where the eggs are defended and cleaned.

Bearers are fish that carry their embryos (and sometimes their young) around with them, either externally or internally e.g. sea horses

Question 42

There are several ways in which females deliver additional nutrients to their young including:

Answer 42

mucoid histotrophy - where embryos feed on mucus produced by the uterus 
placental viviparity (10%) - where species develop a yolk sac placenta after yolk is consumed. 
Oophagy - embryos consume unfertilized eggs produced by the mother. In lamniformes, unfertilized eggs continue to be produced throughout at least a portion of pregnancy. In sand tiger sharks (Carcharias taurus), the first embryo to hatch within each uterus will consume both unfertilized eggs and all other embryos within that uterus.