Fishery Science

themes/components of fishery science

ecology, social systems/politics, economic systems, stock assessment, gear

3 species of thesher sharks

• Pelagic thresher sharks → only one restricted to pacific

  • Vascular plexus

• Bigeye thresher sharks

• Common thresher sharks

life history of thresher

• 3m tl and 88kg

• Eat small sardines, mesopelagic fish, and squid

• Whip tails at prey to hunt

• Females mature at 8-9yrs, males 7-9 yrs

• Ovoviparious - two oophagous young at a time

  • Put additional eggs in utero and baby sharks can eat those eggs so they can stay in utero longer

  • Also intrauterine cannibalism (store sperm and fertilize egg and then older fetus can eat the younger)

• 16-28 yr lifespan

• No muscular rete mirabilis

• Ocular rete mirabilis present

cleaner fish

• Bluestreak cleaner wrasse and moon wrasse

  • Pick parasites off sharks

• Sharks that are there early in the morning when cleaners are hungry, they benefit more

• Thrasher sharks often get parasites in their nose, fins and cloaca

  • They have thin skin

• The two cleaner fish are specialized to clean different areas of the shark (different niches)

• Thrashers need to keep moving so they slowly circle the areas with cleaner fish

thrasher vulnerability

• Fishing, dynamite

• Typhoons

Goal of pelagic thrasher shark research

• Understand pts pop connectivity and turnover

  • Use telemetry to measure daily visitation turnover

• Understand site fidelity as measure of vulnerability

  • Use logging telemetry at cleaner sites

• Begin to measure ecological value of cleaning

  • Use mobile telemetry to find distance swum between visitations

• Further understand of basic life history/ecology

Conclusions of thrasher sharks

• Sharks visiting monad shoal are from a relatively small seasonal group with 42% turnover in 2 months

• Dive businesses are being sustained by visits from 28-32 thresher sharks, approximately 13 of which are likely to remain in the vicinity of the seamount after two months

• Returning almost daily within a month

  • Cleaning is highly values service

• Use a “shark highway”

What is a fishery

• A social ecological system organized around the harvest of wild aquatic fish or invertebrates for use by humans

• Management <-> fishermen <-> fish “stocks” <-> habitat/ecosystems <-> management

Pearl divers

• Traditionally free divers

• Mostly women doing it because they are better at free diving from their physiology

What are human dimensions of fisheries

• The “social” side of social ecological systems (SES)

  • All human aspects (dimensions) of fisheries

• The term “human dimensions” normally used in a SES context

  • Highlight importance of human subsystems

  • Refer to the diversity in human subsystems

What are some broad human aspects of fisheries?

• Tourism

• Recreation

• Fish trade/aquarium trade

• slavery/mafia/piracy

• Classic social sciences (sociology, anthropology, etc), applied social sciences (law, education, communication, etc), arts and humanities (philosophy, art like totem poles, museum work, blown glass fishing gear, etc)

Thinking about fisheries social ecological systems (SES)

SES thinking is increasingly permeating the academic and management sphere

• Viewing fisheries as a comprehensive whole

• Ecological components

• Economic components

• Social components

• Cultural components

• Needs both high-level, multi- and trans-disciplinary thinking and fine-scale research within individual disciplines

• Many human dimensions offices within fisheries still underfunded, should they exist at all

Brief history of people and fish

• Fishing has been around for a long time

  • Hooks made of bone, weights of stone

  • Evidence from Prehistoric, ancient Egyptian

• Many cultures have deep connections to fisheries and their own fishing traditions

  • For many, fishing may be a point of both personal and cultural identity

People have been influencing their environment via fishing for a long time

Overfishing and fisheries management are not modern phenomena

Industrial revolution brought about some major technological advancements to fishing

• Humans able to fish at a level they never fished before

• Additional technology booms post WWI and WWII

• Lead to boatload of issues

  • Pollution and ghost gear

  • Rampant overfishing

    • Biological data, thresholds not available or known for many species

  • International fisheries conflict

Modern times

• 1970-80 saw a series of fish stock collapses and population declines

  • Tragedy of the commons

    • If you know the fish stock can deplete but also that other people are going to keep fishing no matter what, you keep fishing as much as possible before they run out

  • Some fisheries still have not recovered, from either and ecological or social standpoint

Modern fisheries management

The series of fish stock collapses in the 80s led to fisheries management reforms in the US

The magnuson stevens fishery act (MSA) of 1976

• established modern fishery management in the US at the federal and regional levels

  • Ted stevens was a senator from Alaska, encouraged investment into alaska and recognized the value of fisheries in alaska

• MSA has been reauthorized several times, most recently in 2006

• For domestic marine fish stocks

The MSA originally had 5 main goals

• Extend us control of ocean 

• Phase out or limit foreign fishing activity

  • Prevent foreign overfishing

• Recover overfished stocks

• Manage and converse marine fisheries resource

Management boundaries

• Shoreline - 3n mi: state waters

• 3n mi - 12 n mi: territorial sea

• 12 n mi - 200 n mi: exclusive economic zone (EEZ)

Marine fisheries management

• Some fish species and stocks span borders requiring international cooperation for their management

  • Highly migratory species

    • Tunas, bluefins, some species of shark

  • Halibut

international fisheries management commissions conduct stock assessments and allocate quotas to individual nations

Most freshwater fisheries and inland fisheries are managed by state wildlife management agencies

• Do freshwater fish populations typically span state borders like marine ones do? At what physical level does the freshwater fish population occur?

• States oversee all stock assessment, regulation setting, etc

  • Cross border entities typically advisory, ex great lakes fisheries commission

marine fishery reginons USA

• N pacific

• Pacific

• gulf of mexico

• mid atlantic

• south atlantic

• new engtland

freshwater is strictly rec fishing, no commercial

exception with the great lakes

role of public comment

Public comment opportunities are a signature feature of US fisheries management and critical for a variety of reasons

• Foster public buy-in

• Identify stakeholders’ concerns

• Identify new issues previously unknown to management

• Both written and in-person comments can be formally lodged

• As fisheries management and regulation is often contentious, it’s important to make sure all stakeholders have a chance to be heard (ie. listened to)

What Do We Manage For?

Fisheries can be managed for several things

• Ecological outcomes

• Economic outcomes

• Social outcomes (ex. angler satisfaction)

• Proper fisheries management is a balancing act between all of these factors

• Science sets the regulatory boundaries, advises further action

• Social concerns drive the fine-tuning of regulations

Identifying Regulation Preferences - You can go about identifying stakeholders’ regulation preferences in several ways

Focus groups

• Ask people directly!, “What do you think a fair outcome would be?”

Surveys

• (Roundabout) stated regulation preferences, What decisions do people say they’ll make when presented with changes and trade-offs?

Track fishing effort

• Revealed regulation preferences, What do people actually do when regulations change, Must keep other external forces in mind

fish shaped curve

Boom bust is usually accompanied by banking

people get loans for boats to go fishing and then the stocks crash and the fishermen can’t repay their loans —> over capitalization → put more in than you’ll get out

top 10 target species (weight of landing)

• alaska pollock aka walleye pollock

• shipjack tuna

• sardinellas nei

• chub mackerel

• atlantic herring

• yellowfin tuna

• scads nei

• japanese anchovy

the _ is a limiting factor in the ocean/fisheries

sun

highest production is on…

the coasts specifically west coasts of continents, the equator, and boreal

• coasts because of upwelling + nutrients from land runoff

• equatorial because equatorial upwelling

• boreal because 24hr sun in summer and land mass density

world fishery landings peaked in the

80s

life history

• investment strategy

• in aspects of energy allocation that will yield the best chance of reproducing the most or best fitted offspring

• feeding, digestion, fertilization, growth, different tissues, behaviors, movement, color pigments, egg/sperm, storage, repetition/cycling/timing

life history evolution is analagous with

the economy development under a free market where calories are coinage

life history example

• larval phase or fry (not synonymous)

• settlement → squamation, pigmentation, habitat change, form change

• juvenile to subadult phase

• spatial temporal segregation

winter vs summer flounder life history

• diff species and families

• winter drop sticky tendril eggs that are non buoyant, no need to have larvae come in and out of estuary like summer have to

evolution of repro mechanisms trades risk and reward in

• fertilization (internal/external)

• sexual dimorphism + hermaphroditism

• courtship behavior

• size and ecological constraints on gamete, spawning, and parental care investment

sharks, skates, and rays have internal fertilziation

claspers

females can store, move, reject sperm

need lots of sperm to fert egg

with external fert, the egg and sperm are diluted in the water so if groups expel their egg/sperm all at once, the dilution is less

internal fert cost

• anatomical constraints

• copulation effort

• gestation

• few offspring

internal fert benefits

• targeted

• selective

• full development

• high survival

external fert costs

• gamete production

• wasted gametes

• multiple paternity

external fert benefits

• lottery effect

• increases with size

• multiple paternity - diverse gene pool

size determines gamete, spawning, parental care investment

• broadcast spawning

• migration

• brooding

• iteroparity/spawns once vs semelparity/spawns multiple times

mate access - bateman’s principle

• variability in spawning success is greater in females than males

• female fecundity (how much offspring per individual) is limiting factor in reproductive output, thus males must compete for female access

conspicuous consumption

• peacock phenomenon (male peacocks have colorful feathers to attract mates but risk predation)

• indication of good gene set

symmetry

indication of good gene set

indeterminate growth

• continual increase in length and volume

• linked to egg size, egg quality, egg number (fecundity and clutch size), itero vs semelparity, age and size at maturation, longevity, parental care, sex change, migration potential

hermaphrodite - protogynous

female first

hermaphrodite - protandry

male first

nesting

place based, requires attraction to nest, requires guarding at cost to eating, yields more advanced and larger young

courtship behavior

promiscuity, monogamy/pair bonding, polygyny and territoriality, harem maintenance, lek formation, sneaking and streaking, role of sounds, color, movement to display fitness

general patterns

• more eggs → bigger female eg cod, strugeon

• more/better territory → bigger male eg black sea bass

• cheat → smaller male eg spotted sand bass

• farther migration → bigger both sexes ex pacific salmon

• variable environment → longer life eg striped bass

• predictable environment → shorter life eq pacific salmon

life history - summer flounder pelagic phase

Eye migration begins at ~13 mm

• Corresponds with movement(?) to estuaries

• Can bury, vertically migrate by Stage H

• Selective tidal stream transport?

life tables and survivorship curves

• S_x = n_(x+1) / n_x

• Survivorship = l_x = n_x / n₀

• mortality rate = m_x = l - S_x

• mean # alive in year = L_x = (n_x + n_(x+1) ) / 2

• avg life expectancy = X + e_x

• average remaining life expectancy = e_x

• avg life expectancy for individuals of age X

ottolith

earbone, has growth rings that can be used to determine age and other info

fatal to remove, can sometimes use scales instead for some fish (only fish that do not frequently shed scales)

tetracycline

stains bones green, can see how much bone/layers there are since green

long term data sets ex

• ichthyoplankton sampling

• 1991-2020

• weekly

• 1m diameter x 1mm mesh

• at night

• 3 x half hour set

• flow quantified

• fished passively from bridge during incoming tide

• data expressed as catch per unit effort (CPUE)

• provided weekly snapshot

what accounts for recruitment (how many new fish you have in the fishery) variation - Critical period hypothesis

johann hjort, 1904

if fish feed when the tolk sac is used up, they surviive

what accounts for recruitment (how many new fish you have in the fishery) variation - Aberrant drift hypothesis

1926

current do or do not take larvae to nursery

what accounts for recruitment (how many new fish you have in the fishery) variation - match mismatch hypothesis

david cushing, 1969

timing of fish hatch must match logged timing of phytoplankton bloom

what accounts for recruitment (how many new fish you have in the fishery) variation - stable ocean hypothesis

ruben laser, 1978

ocean is calm enough at time of first feeding that stratification allows food concentration

what accounts for recruitment (how many new fish you have in the fishery) variation - lottery hypothesis

peter sale, 1978-91

bottleneck happens at recruitment/transformation

what accounts for recruitment (how many new fish you have in the fishery) variation - density depending

compensation/decompensation

movement

• dispersal - one way movement populates new space, includes reef resident larvae

• ranging - movement within and around a home

• range kernel - locally cued, typically for foraging or degradation of local conditions

• migration - 2 or more way predictable/compulsive, undistracted, between habitats that offer different resources; genetically cued or learned, may require leaving perfectly good environment for unknown conditions

importance of habitat

• predation refuge

• juvenile rearing/nursery habitat

• spawning substrate

habitat mediates predation

• ex: split lake in half, removed all woody debris from one half

• largemouth bass consumed less fish, ate more terrestrial prey and grew more slowly → area with wood (?)

biogenic habitat

coral, kelp

pelagic habitat

just as important, but more dynamic and different anthropogenic impacts

epipelagic

sunlight, photosynthesis

mesopelagic

minimal light, twilight zone

bathypelagic

no natural light from sun

nektonic

not drifters, can move on their own

vagile

fast swimmersn

natant

swimming, in water column

tragedy of the commons

an economic and environmental concept where individuals use a shared resource for personal gain, which eventually overuses and destroys the resource for everyone

flotsam and fish aggregating devices

free floating algae when in reproducing stage, dormant when youngd

diel vertical migration

• night → epipelagic, able to feed

• day → mesopelagic, avoid predators

• predation can change DVVM behavior

essential fish habitat

• legal term

• NOAA identifies important habitat and can act to control fishing impacts on the habitat or restore habitat, but generally does not manage most threats to habitat

endangered species act

ESA has teeth when it comes to protecting fish habitat

habitat loss

• slr

• shoreline hardening

• development

passive gear

gear does not move, fish come to gear

• bait hook and line

• trap

• clay pot

• gill and trammel net

• fish wheel

• weir

• fyke net

active gear

gear chases fish down to capture it

• trawl net

• beam

• otter (paired, rockhopper)

• seine net, purse or beach

• diving,

• spearing

• casting popnet

• dredge

• blast

measuring catch per unit effort

• active gear → area swept, volume cleared, distance swept, time swept

• passive gear → gears/lengths deployed, soak time, problems: not linear catch rates, saturation, priority effects

size structured predation

most fish swallow prey whole

trophic ontogeny

genetic life history of development, shift of what you eat with age

optimal foraging theory

the idea that fish should forage in ways that maximize the ratio of benefits to costs

costs: handling time, foraging time, predation risk

benefits: amount of food, gross energy intake, net energy gain, growth

predator must be able to recognize diff types of prey and “estimate” the energy gain