Reference Points

Question 1

What is a reference point?

Answer 1

a conventional value, derived from technical analysis, which represents a state of the fishery or population, and whose characteristics are believed to be useful for the management of the unit stock

Question 2

What are reference points typically based on?

Answer 2

fishing mortality rates (F), biomass levels (B), or recruitment indices

Question 3

What are reference points used for?

Answer 3

used to determine allowable effort and harvest

-important that reference points are agreed upon by managers and fishery stakeholders.

Question 4

What are the three reference points used?

Answer 4

Target Reference Point (TRP)
Limit Reference Point (LRP)
Trigger (or Threshold) Reference Point

Question 5

Target Reference Point (TRP)

Answer 5

indicates a state of a fishery and/or a resource that is considered desirable and at which management action should aim

include economic or social considerations (ideal state of fishery) in addition to biological criteria

Question 6

Limit Reference Point (LRP)

Answer 6

indicates a state of a fishery and/or a resource that is considered undesirable and which management action should avoid

Includes on only biological based

Question 7

Trigger (or Threshold) Reference Point

Answer 7

set between TRP and LRP to promptadditional management response to help ensure fishery remains close to target and/or avoidsbreaching limit

Question 8

MSY stand for

Answer 8

Maximum sustainable yield

Question 9

Maximum sustainable yield

Answer 9

largest amount of resource that can be taken continuously without causing a population decline

Question 10

What are some reference points based around MSY

Answer 10

BMSY or X%BMSY
FMSY or X%FMSY

Question 11

BMSY or X%BMSY

Answer 11

biomass at MSY or X% MSY

Question 12

FMSY or X%FMSY

Answer 12

fishing mortality rate that leads to BMSY or X% fishing mortality rate that leads to BMSY

Question 13

How can MSY reference points be produced?

Answer 13

from a variety of population models (surplus production, age-structured) and are considered more data-intensive as compared to alternatives

Question 14

MSY in fisheries management

Answer 14

now more often used as a limit

Question 15

Pretty Good Yield

Answer 15

Considerable uncertainty both in stock size and harvest rate that achieve MSY as well as in ability to manage for MSY

Pretty good yield → 80% of MSY

Question 16

PGY occur

Answer 16

Occurs over broad range of stock sizes and harvest rates

Question 17

What does PGY depend on?

Answer 17

steepness of S/R curve (productivity of stock when fished to low level)

Question 18

Fmax and F0.1

Answer 18

Based on yield per recruit (YPR) curve → how changes in exploitation rate affect lifetime expected yield of an individual recruit or cohort

Question 19

Fmax

Answer 19

fishing mortality rate that maximizes YPR

Question 20

F 0.1

Answer 20

fishing mortality rate where slope of YPR curve is 10% slope at origin

Question 21

F 0.1

Answer 21

is more conservative and may be a target or limit reference point

Question 22

Fmax

Answer 22

(when used) is typically a limit

Question 23

YPR curve depends on

Answer 23

growth, natural mortality, and age-specific fishery selectivity (relatively low data requirements)

Question 24

Fmax , F0.1 used where

Answer 24

growth overfishing is a concern

Question 25

What is the downside to Fmax , F0.1

Answer 25

does not consider recruitment overfishing and may lead to fishing mortality rates that are too high

Fmax , F0.1 can be > FMSY

Question 26

Recruitment based reference points

Answer 26

FX%
Fmed

Used as reference points for recruitment overfishing

Question 27

FX%

Answer 27

fishing mortality rate that reduces stock to X% of maximum spawning potential

Can be target or limit (for target, X typically 40-50%, whereas limit is lower)

Question 28

Fmed

Answer 28

fishing mortality rate that corresponds to median value of stock-recruit ratio

Question 29

What are the data requirements for both recruitment-based reference points?

Answer 29

Minimal data requirements (natural mortality, age-specific fishery selectivity and fecundity); possible to use life history correlates

Question 30

FMEY

Answer 30

fishing mortality rate that produces maximum economic yield

Question 31

Index or empirical reference points

Answer 31

points such as historical CPUE values (e.g., median) are occasionally used; often easier to understand though more error-prone

Question 32

Multispecies Biological Reference Points

Answer 32

Single species reference points
Multispecies Maximum Sustainable Yield (MMSY)

Question 33

Single species reference points

Answer 33

can be fit into multispecies framework using models that incorporate multispecies interactions, e.g., include predation mortality (often referred to as “M2”) in determining FMSY or FX%

Question 34

MMSY

Answer 34

incorporates predation and trophic relationships (bioenergetics) in estimating MSY across species/system → often (but not always) found to be less than sum of single species MSYs

Question 35

Examples of reference points based on environmental conditions:

Answer 35

Pacific sardine effort targets depend on sea-surface temperature

Question 36

Atlantic menhaden example with an environmental reference point - why?

Answer 36

Atlantic menhaden supports an important commercial reduction fishery as well as a growing bait fishery

Menhaden are also an important prey item for several species (e.g., striped bass, bluefish)

Single species reference points based on fecundity had been used until 2020; menhaden above threshold since 1991

2021/2022 TAC based on ecological reference points

Question 37

Atlantic menhaden example with environmental reference point - resolution

Answer 37

Ecological reference points (ERPs) evaluated using the Northwest Atlantic Coastal Shelf Model of Intermediate Complexity for Ecosystems (NWACS-MICE)

Menhaden target and threshold fishing mortality rates are a function of striped bass biomass and fishing mortality target

Question 38

Northwest Atlantic Coastal Shelf Model of Intermediate Complexity for Ecosystems (NWACS-MICE)

Answer 38

Includes four key predators (striped bass, bluefish, weakfish and spiny dogfish) and three key prey (menhaden, Atlantic herring, and bay anchovy)

Question 39

Harvest control rules (HRCs)

Answer 39

Guidelines for allowable catch, effort, or fishing mortality based on fishery reference points

Pre-agreed upon management response thought to increase efficiency and transparency of management process

Question 40

How are HCRs assessed?

Answer 40

compared through management strategy evaluations (MSEs)

Question 41

MSE is what type of approach?

Answer 41

simulation

can be used to evaluate assessment models in comparison to “true” stock abundances as well as to determine what decision rules are most effective in meeting target reference points

Question 42

What do MSEs generally allow for?

Answer 42

“implementation error” → HCRs/management measures not perfectly implemented