A stock assessment is the process of collecting, analyzing, and reporting demographic information to determine changes in the abundance of fishery stocks in response to fishing and, to the extent possible, predict future trends of stock abundance.

1. Philippines' National
Stock Assessment
Program

2. Stock Assessments Basic Concepts
Introduction
The importance of a country's fisheries cannot be measured solely by
their contribution to GDP; rather, fisheries services and products are
essential components of human feeding and employment. The capacity of
fisheries resources to be replenished is another aspect that contributes to
their value. In contrast to mineral resources, the length of fishery resources
or any other biological resources is virtually limitless if well handled. A
significant conclusion is that the biological characteristics, which are the
primary obiective of fisheries stock assessment, are the fundamental basis
for conservation and management of fisheries resources.

3. Learning Objectives
o Define what is fish stock assessment and other terminologies used in the
field of fish stock assessment;
o Determine why fish stock assessment is important;
o identify and differentiate the information needed in the fish stock
assessments based on models of fish population;
o Determine the factors affecting data collection and assessment of wild
fish stocks;
o Determine the different biological reference points used when conducting
estimation of wild fish stocks.

4. What is Stock Assessment?
 Stock assessment is the process of collecting, analyzing, and
reporting demographic information to determine changes in the
abundance of fishery stocks in response to fishing and, to the
extent possible, predict future trends of stock abundance.
Managers use stock assessments as a basis to evaluate and
specify the present and probable future condition of a fishery.
 fish population is a group of individual fish of a single
interbreeding species located in a given area, which could be as
large as the Atlantic Ocean or as small as a single river.

5.  A biological fish stock is a group of fish of the same species that
live in the same geographic area and mix enough to breed with each
other when mature.
 A management stock may refer to a biological stock, or a multi-
species complex that is managed as a single unit.
Within a fish stock or population, a cohort is a group of fish all
born in the same year. For example, Within the Gulf of Maine cod
stock, all of the cod born in 2004 belong to one cohort and those born
in 2005 comprise a second cohort.
Fisheries' scientific stock assessments are key to fisheries
management. They examine the effects of fishing and other factors to
describe the past and current status of a fish stock, answer questions
about the size of a fish stock, and make predictions about how a fish
stock will respond to current and future management measures.

6.  Population assessments allow us to evaluate and report the status of
managed fisheries, marine mammals, and endangered/threatened species.
species.
The mathematical and statistical techniques used to perform a stock
stock assessment are referred to as the assessment model. Scientists compare
compare different assumptions within a given assessment model and may also
may also examine a variety of different assessment models.
Importance of stock assessment:
o provide important science information necessary for the conservation and
conservation and management of fish stocks
Stock assessments are based on models of fish populations that require
require three primary categories of information: catch, abundance, and biology.
and biology.

7.  Catch Data
refers to the amount of fish removed from a stock by fishing.
A national network of fishery monitoring programs continuously
collects catch data and makes this information available to stock
assessment scientists and managers.
Sources of catch data include:
o Dockside monitoring
o Logbooks
o Observers
o Recreational sampling

8. o Dockside monitoring
Often conducted in partnership with the different agencies.
Dockside monitoring records commercial catch receiots to give an
accurate measure of commercial landings and provides biological
samples of the length, sex, and age of fish
o Logbooks
Records from commercial fishermen of their location, gear, and catch.
o Observers
Biologists observe fishing operations on a certain proportion of fishing
vessels and collect data on the amount of catch and discards.
o Recreational sampling
Telephone interview surveys and dockside sampling estimate the level of
catch by the recreational fishery

9. Abundance Data
is a measure, or relative index, of the number or weight of fish in the
stock.
Data ideally come from a statistically-designed, fishery-independent
survey (systematic sampling carried out by research or contracted
commercial fishing vessels separately from commercial fishing
operations) that samples fish at hundreds of locations throughout the
stock's range. Most surveys are conducted annually and collect data on
all ecosystem components.

10. Biology Data
provides information on fish growth rates and natural mortality. Biological
data includes information on fish size, age, reproductive rates, and
movement.
Annual growth rings in fish ear bones (otoliths, pictured on right) are read
by biologists in our laboratories. The samples may be collected during
fishery-independent surveys or be obtained from observers and other fishery
sampling programs. Academic programs and cooperative research with the
fishing industry are other important sources of biological data.

11. Ecosystem Factors and Stock Assessments
Factors other than fishing can have an influential role in determining the
health and abundance of fish stocks.
 Food web.
All species within an ecosystem are connected to each other by the
things that they eat, and the things that eat them. Because of these
connections. the population dynamics of one species can affect the
dynamics of many other species.
A food web describes the connections between different species in an
ecosystem through predator and prey relationships. Understanding these
interactions can provide context for interpreting stock assessment results.
Output from food web and predator prey models can provide input to a
single species assessment models, for example, the time series of natural
mortality, providing improved stock assessment outputs.

12.  Competition and Other Species Interactions
Species Interactions other than predator prey relationships can abo
influence population dynamics. Because resources within marine
ecosystems are limited, animals must compete for food and space.
Because of competition, the total production of a system may be more
limited than one might expect if each species is considered alone
 Habitat
Healthy habitats sustain marine and coastal species, communities, and
economies. Alterations, including through development, dredging,
pollutants, or natural disasters; impact food sources, cover, refugia, and
breeding grounds which are vital for reproduction, growth, metabolism,
and other vital rates of marine species. Because habitat plays such a large
role in structuring populations, understanding fish interactions with their
habitat is important to stock assessment.

13.  Physical Environment
In addition to physical habitat (e.g., bottom type), variability in ocean
and climate patterns should also be taken into account when examining
fish stocks. Many fish species have a relatively narrow range of
temperature, chemical and other physical tolerances. Disruptions in the
physical environment, due to climate or other perturbations, can impact
natural stock behaviors such as spawning and migration.

14. The following are necessary to assess a fish stock:
o The appropriate data bases
o Analyses of the available data
o Short and long-term projections of the yield and biomass vihotion
o To determine long-term biological reference points
o To estimate the short and long-term effects on yield and biomass of
different strategies of the fishery exploitation
The different steps to assess a stock can be summarized as
follows:
1. To define the objectives of the assessment according to the
development phase of the fisheries and the available information;
2. To promote the collection of information;
a) fishing effort (number of trips, days, tows, time spent fishing,
etc.), and characteristics of the gears used.
b) Types of operation of the fleets and of its fishing gears, etc

15. Continuation…
c.) Biological sampling in the landing ports.
d.)Biological sampling (and information about the fishing operation)
on board commercial vessels.
e.)Biological sampling on board research vessels.
3. To analyze the stocks
The knowledge gained about the resource and the available basic
data, determine the type of models that should be used and
consequently the type of analyses that can be done.

16. Biological Reference Points
It is a concrete number, a value for stock size or fishing mortality. It
serve as a way to judge those estimates based on knowledge and
assumptions about the species' growth, reproduction and mortality.
Fishing mortality rate
It is the rate at which fish are removed from the stock by harvesting.
Biological reference points based on fishing mortality help managers keep
the withdrawal rate at a level that will ensure the long-term production or
stability of the stock.
Maximum Sustainable Yield (MSY)
serves as the foundation for most biological reference points. The
maximum sustainable yield is typically thought of as the largest average
catch that can be continuously taken from a stock under existing
environmental conditions.

17. o Stock assessment scientists and decision makers use the letter B to
denote biomass. Biomass, the total weight of the fish in a given stock.
o Occasionally, rather than total biomass, scientists will refer to the
spawning stock biomass. Spawning stock biomass (SSB), the total
weight of the reproductively mature individuals in the stock.
o The term BMSY is used to indicate the stock size that can produce the
maximum sustainable yield.
o The term SSBMSY indicates the size of the reproductive mature portion
of the stock that will produce the maximum sustainable yield. Similarly.
the letter F denotes the fishing mortality rate
o FMSY indicates the fishing mortality rate at the level that would maintain
the maximum sustainable yield for a stock at BMSY

18. Deviations from the targets may or may not result in changes in policy.
Control rules, designed by scientists but chosen by managers, guide the
ways in which the fishing mortality rates are adjusted over time based on
the status of the stock.
Thresholds are also referred to as limits, especially in the realm of
international fisheries policy. A threshold is often defined as a specific
fishing mortality rate or stock size that is some fraction of BMSY.
Two of the key questions that a stock assessment aims to address are
whether overfishing is occurring and whether the stock is in an overfished
state.

19. Philippines' National Stock Assessment
Program
Introduction
"The National Stock Assessment Program (NSAP) was
conceptualized due to the lack of standardized and continuous
information on fishery resources which is fundamental to fishery
management and the apparent institutional incapacity of the Regional
Field Units to conduct resource assessment studies in their respective
areas of jurisdiction"
-Noel C. Barut.

20. The National Stock Assessment Program (NAP) was first
conceptualized in 1995 by Mr. Noel C. Barut, who was then the Chief of
the Pelagic Section of the Fisheries Resources Research Division of the
Bureau of Fisheries and Aquatic Resources (BAR). He is now regarded as
the "Father of NSAP”
Accomplishments of the NSAP:
o Fisheries Report under The 4th National Report to the Convention on
Biological Diversity of the Republic of the Philippines entitled "Assessing
Progress Towards the 2010 Biodiversity Target" in 2009
o Technical Paper Series published by the
BAR National Fisheries Research and Development Institute in 2009.
Six 16) technical papers on the fish stock assessment of Honda Bay.
Lagonoy Gulf, Northem Zambales, Sorsogon Bay. and Visayan Sea
were featured.

21. o Two (2) conferences that the NAP organized to showcase the many
results of the stock assessment studies conducted by the various NAP
teams at the national and regional levels in 2011 and 2014.
o Development of the NSA Database system was initiated in 1997 by Mr.
Valeriano Manlulu with the help of Dr.
Peter Williams of the South Pacific Commission following the Landed
Catch and Effort Monitoring framework of the Program. It was only in
2014 that server database was established.
o NSAP has provided information in support of numerous management
strategies at various levels, whether local, regional, national and/or
international. This includes:
• Sardine seasonal closure in Zamboanga (DA BFAR FAO 255 s. 2014)
• Small pelagic conservation in the Davao Gulf (JAO 2 s. 2014)
•. Round scads seasonal closure in Northern Palawan (JAO 1 s. 2015)

22. Sampling methods and strategies:
Data collection by sampling method can be done through random
sampling whereby samples are acquired in a random manner. In such
sampling operation, all observations in the fish population are given the
same probability of being sampled. In the case of a very big landing area
that the assigned enumerators cannot possibly record all the fishing boats
that are landing, a stratified random sampling maybe applied.
Data collected:
1. Catch & effort. This is the overall landings and fishing activities within the
sampling area. This can be done through direct interview with the
fisherman or fishing operator. The three main points of conversation are:
total landed catch (by boat, by gear): type of fishing gear used leg. Ring
net, purse seine, surface gillnet, Handline, etc.); and fishing effort (e g.
number of hauls, number of hours fishing. etc.)

23. 2. Total sub-sample weight and weight of each species group.
This can be done by borrowing sub-samples from the catch by gear.
Know the total sub-sample weight then sort to species group
identify to species level and use Scientific Name e.g.
Nemipterus japonicus, Decapterus macrosoma) and get the weight
of each species group.
3. Length measurements by species by gear. All the species in the
sub-sample can be measured immediately or only selected
commercially or dominant species.

24. Source of catch & effort data:
 Survey at landing center
The data are collected by the enumerators at the landing site through
direct interview with the fishermen to obtain information on when, where,
how much of the fish were caught by what fishing gear and how much effort
was used, etc. This method is usually effective only for coastal fisheries,
which operates near shore and take a trip for a day or few days only since it
depends mostly on the fishermen's memory.
 Survey by logbooks - This method is effective for large-scale fisheries (ie.
commercial boats), particularty for boats that stay in the fishing ground for a
considerable length period (e g. Purse Seiners). Data on catch & effort are
recorded thru logbook system.

25. Classification of major and minor fish landing sites depends on the
bulk of boat landings.
Major fish landing sites have more number of boat landings than minor
fish landing sites and a combination of commercial and municipal boats
maybe landing in the area. In the case of commercial and municipal landing
sites, only commercial boats (with more than 3 GT) are being monitored in
the commercial landing site and municipal boats (weighing 3 GT or less) in
municipal landing site.

26. NSAP Data Forms
All essential data elements are collected and recorded in standard
forms. The data will be encoded and processed using the developed NAP
database. The length frequency data can be analyzed using FISAT
Program or by using other assessment programs. The basic design of the
NSA forms was adopted from the Food and Agriculture Organization
(FAO) and was also used by the other assessment projects of BFAR i.e.
Tuna Project, and Small Pelagics Management Program.

27. NSAP Data Forms
o NSAP Form 1:
Monthly Report (Landing by Gear & Length Frequency)
o NSAP Form 2:
Fish Landing Survey Form (Catch & Effort)
o NSAP Form 2a:
Landed Catch & Effort Monitoring (Weight Measurement)
o NSAP Form 2b:
Landed Catch & Effort Monitoring (Length Measurement)
o NSAP Form 3:
Length Frequency Tally Sheet
o NSAP Form 4:
Boat Particulars
o NSAP Form 5:
Gear Particulars

28. o SAMPLE SERIAL NUMBER
Refers to the serial number of the fishing boats monitored.
o BOAT NAME
The name of the boat that operates in fishing. If the boat has no
name, as in the case of some non-motorized boats, the name of the
fishing operator or fisherman may be used provided it is constantly used
for that particular boat. The boat will be classified according to gear
type.
o FISHING GEAR
The type of fishing gear used in catching fish.
o FISHING EFFORT
The fishing power exerted to capture/harvest the fish in a given
fishing area.

29. Coverage Catch and terms used:
o DATE. Refers to the date of sampling
o LANDING CENTER. The assigned landing site during sampling schedule.
It can either be commercial, municipal, major, or minor landing center.
o FISHING GROUND. The water where the fishing boat operated or where
the fishes are caught.
o ENUMERATORS. The name of the data collectors assigned in the
designated landing area
o NO. OF SAMPLES. The total number of boats sampled for length & weight
measurements.
o SAMPLE SERIAL NUMBER. Refers to the serial number of the fishing
boats monitored.

30. Common Used Fishing Gears and Measures of Effort
Fishing Gears Fishing Effort
trawl Number of hours, dragging
hours
Purse seine, ringnet, bagnet,
beacg seine
Number of hauls, fishing hours
Danish seine Number of Hauls
Bottom gill net, drift gill net,
surface gill net
Length of net in meters (number
of banata), number of hours
setting
Lift net Number of hauls, soaking time

31. Common Used Fishing Gears and Measures of Effort
Fishing Gears Fishing Effort
Multiple hook and line, hook and
line, longline
Number of hooks, number of sets,
soaking time
handline Number of hours fishing, numbers of
line, number of days fishing
troll line Number of lines, number of hours
fishing
jigger Number of spear used, diving hours
Fish pot, fish corral, and other fixed
gears
Number of hours during which the
gear was in the waters, numbers of
hauls per day, number of unit

32. Gear particulars:
o Unit of catch (Weight): Record total catch in kilograms or metric tons
while the sub-sample weights in grams
o Total boat catch: The quantity (actual estimation) of fish catch by a
particular fishing boat per fishing gear. The weights of the species in
the catch composition (Market Categories) are summed up to get the
total catch: No. of Boxes and weight in Kg
a) No. of boxes. Refers to the number of fish containers used. The
containers can be in the form of boxes, bañeras, foams, etc.
b) Weight in Kg: Actual estimated weight of catch per boat, per
gear. If fish catches are in containers, the standard weight of
each container can be determined by asking the fishing
operators, fishermen or fish buyers.

33. Continuation…
...the actual weight of each container with fish, varies depending on the
amount of fish and the proportion of water and ice present. In this case, the
estimated weight of the catch in each container can be determined by
carefully pushing down the fish with the palm. Then, estimate the weight of
the fish in the container minus the water and ice.
o Total Sample: The quantity of fish sub-sampled for species composition
in weight, and for length measurements by fishing boat & by fishing
gear.
a) No. of Boxes: Refers to the number of containers where fish sub-
samples were taken for length & weight measurements.
b) Weight in Kg: The total weight of the sub-samples taken.

34. o Catch compostion Market Categories (Boxes/ Kg.)
Refers to the species composition in the catch of the boat by gear with
corresponding (Boxes/Kg.) weight by species. If possible, scientific name
is used. The estimated catch (under the catch composition) should tally
with the number of boxes and weight found in the column of the total boat
catch.

35. Landed Catch and effort Monitoring (LengthMeasurement)
* Measuring board- suitable tool for measuring particularly,
smaller fish.
* Caliper- is usually used for measuring invertebrates. in the
case of big tunas and billfishes, an improvised caliper made
of wood can be used.

36. Types of Length Measurement:
Total Length- the distance from the tip of the snout
to the of the caudal fin. used for fish with soft caudal
fin.