🚧 Under construction — VoTechWorks is being built. A free tech program — complimentary, as our commitment to get America working.
voTechWorksGrade 13 · a vocational technology learning center, by urbanicity
newSchoolWorks.com › VoTechWorks › Agriculture, Environment & Public Service › Aquaculture & Marine Science Tech › Hatchery Operations: Broodstock to Juvenile Production › Lesson 12
AGR-AQUA50-04 · Lesson 12 · 18 clock hours · lab

Integrated Hatchery Operations: Full Production Cycle Lab

Objective. Students will independently manage an assigned hatchery tank system for a minimum 10-day integrated production run, executing all daily tasks—water quality, feeding, sampling, live-feed preparation, and record-keeping—and presenting a final cohort report.

⚠ Pending professional review

This lesson, its worked examples and its practice questions has not yet been verified by a licensed professional in the field or by a certification or approval body. It is a study draft and may contain errors. Do not use it as instructions for work on a job site or on live equipment. Always follow your instructor, your supervising professional, and current official references and regulations.

VoTechWorks program approval and accreditation are still in progress. Credentials are issued only by the certifying bodies named in each program, after their own exams.

Integrated Hatchery Operations: Full Production Cycle Lab

This lab places you in the role of hatchery technician for a real, continuous production run. Over ten consecutive weekdays you will independently manage an assigned tank system, making every operational decision that keeps your cohort alive and growing. The skills you practice here are the same ones commercial aquaculture employers expect on day one.

The Morning Task Sequence

Every hatchery shift starts the same way, and that consistency is not habit—it is science. Complete the following in order within your two-hour morning window:

1. Water quality sweep. Measure temperature, dissolved oxygen (DO), pH, salinity or conductivity, and ammonia-nitrogen (NH₃-N). Record each value with the time and meter ID in your production log before you do anything else. If a value is out of range, do not wait—flag it immediately and begin your four-hour response clock.

2. Mortality count and removal. Net or siphon all dead animals. Count and record them. Remove carcasses promptly; decomposing tissue drives ammonia spikes and pathogen load.

3. Feeding. Deliver the correct ration for your species and life stage. Feeding rate is typically expressed as a percentage of estimated biomass per day. Calculate the ration, weigh or measure it, deliver it, and log the amount.

4. Log entry. Every action taken, every measurement, every observation goes in the log at the time it happens—not reconstructed from memory at the end of the day. Gaps in the log are gaps in the data and will fail the check.

Water Quality Thresholds and Deviation Response

Instructor-designed excursions will occur at least once during your run. When any parameter crosses its posted threshold, you have four hours to complete the full deviation response: identify the parameter and magnitude, list three plausible causes, select and implement a corrective action, and record the outcome.

Common causes of excursions and typical corrective actions:

Your response log entry must be specific: the exact value measured, the threshold it crossed, the action taken, the time action was completed, and the follow-up measurement confirming correction.

Live-Feed Preparation

Many larval and early-juvenile stages require live feeds—Artemia nauplii, rotifers, or cultured microalgae—because they cannot yet digest dry formulated diets. Prepare live feed according to the posted protocol for your species. Key points:

Growth, Survival, and Feed Conversion Ratio

Three metrics define cohort performance and form the core of your final report.

Survival rate (SR%) = (number alive at end ÷ initial stocking number) × 100

Specific growth rate (SGR, % body weight per day) = [(ln W₂ − ln W₁) ÷ number of days] × 100, where W₁ and W₂ are mean weights at the start and end of the period.

Feed conversion ratio (FCR) = total dry feed fed (g) ÷ wet weight gain of cohort (g). A lower FCR means the animals converted feed to body mass more efficiently.

Sample animals mid-run (day 5) and at the end (day 10). Record individual weights from a representative subsample of at least ten animals. These data points give you your growth curve and allow SGR and FCR calculation.

Record-Keeping Standards

Your production log is a legal and operational document. Write in ink. If you make an error, draw a single line through it, initial it, and write the correction. Never erase or use correction fluid. Date and time every entry. Instructors can tell the difference between a log filled in real time and one reconstructed at the end of the week—the former shows varied handwriting, notes, corrections, and response times; the latter does not.

Cohort Report Presentation

On day ten you present a five-minute summary to the class. Your report must include:

Be concise. Five minutes is not long; practice your delivery.

Safety in the Hatchery

Slip hazards are constant wherever water is handled. Wear closed-toe, non-slip footwear at all times on the wet floor. When handling chemicals (ammonia test reagents, chlorine for equipment sanitation), wear nitrile gloves and safety glasses. Inspect electrical cords and outlets for water contact before energizing equipment—water and electricity kill. If a cord or outlet shows any sign of water exposure, do not touch it; de-energize the circuit at the breaker using lockout/tagout procedures and notify your instructor. Lift heavy feed bags and equipment with a straight back and bent knees to avoid musculoskeletal injury.

Key terms9

Feed Conversion Ratio (FCR)The mass of dry feed delivered divided by the wet weight gain of the cohort; a lower number indicates more efficient conversion of feed into animal biomass.
Specific Growth Rate (SGR)A standardized daily growth metric expressed as percent body weight gained per day, calculated from the natural logs of beginning and ending mean weights over a defined period.
Survival Rate (SR%)The percentage of stocked animals still alive at a given point in the production run, calculated as (final count ÷ initial count) × 100.
Dissolved Oxygen (DO)The concentration of oxygen gas dissolved in water, typically measured in mg/L; a critical water quality parameter because most aquatic animals require adequate DO for respiration.
Ammonia-Nitrogen (NH₃-N)The unionized form of ammonia dissolved in water, which is acutely toxic to fish and invertebrates at relatively low concentrations; a key indicator of organic loading and biofilter performance.
Live FeedLiving organisms—such as Artemia nauplii or rotifers—fed to larval or early-juvenile aquatic animals that cannot yet efficiently digest dry formulated diets.
Production LogThe chronological written record of all measurements, observations, actions, and outcomes for a hatchery tank system; serves as both an operational tool and an auditable document.
Deviation ResponseThe structured process of identifying an out-of-range water quality parameter, documenting possible causes, implementing a corrective action, and recording the verified outcome within a defined time window.
BiofilterA biological filtration component—commonly a packed bed or moving bed media—colonized by nitrifying bacteria that convert toxic ammonia to nitrite and then to less harmful nitrate.

Worked examples4

1. At stocking (day 0), a tank holds 500 juvenile tilapia with a mean weight of 2.0 g each. At day 10 the mean weight is 3.2 g and 475 fish are counted alive. Calculate the survival rate and the SGR for this cohort.
  1. Step 1 — Survival rate: SR% = (475 ÷ 500) × 100 = 95.0%
  2. Step 2 — SGR uses natural logs of the mean weights. ln(3.2) ≈ 1.1632; ln(2.0) ≈ 0.6931
  3. Step 3 — SGR = [(1.1632 − 0.6931) ÷ 10] × 100 = [0.4701 ÷ 10] × 100 = 4.70% body weight per day
Answer: Survival rate = 95.0%; SGR = 4.70% body weight per day.
2. Over the same 10-day run, you delivered a total of 85 g of dry feed. At day 0 the cohort biomass (500 fish × 2.0 g) was 1,000 g. At day 10 the cohort biomass (475 fish × 3.2 g) is 1,520 g. Calculate the FCR.
  1. Step 1 — Calculate wet weight gain: 1,520 g − 1,000 g = 520 g
  2. Step 2 — FCR = total dry feed fed ÷ wet weight gain = 85 g ÷ 520 g ≈ 0.163
  3. Step 3 — Interpret: an FCR below 1.0 is common for juveniles receiving high-moisture live feed or when wet-weight gain is large relative to dry feed; confirm your feed records are complete and units are consistent.
Answer: FCR ≈ 0.16 (rounded to two decimal places), meaning roughly 0.16 g of dry feed was used per gram of wet weight gained.
3. You measure ammonia-nitrogen (NH₃-N) at 0.8 mg/L this morning; the posted threshold for your species is 0.5 mg/L. You perform a 20% water exchange on a 200-liter tank using source water that tests at 0.0 mg/L NH₃-N. What is the expected NH₃-N concentration immediately after the exchange, assuming perfect mixing?
  1. Step 1 — Volume removed: 20% of 200 L = 40 L removed; 160 L of original water remains.
  2. Step 2 — NH₃-N remaining in tank after removal: 160 L × 0.8 mg/L = 128 mg of ammonia-nitrogen.
  3. Step 3 — Add 40 L of clean water at 0.0 mg/L: no additional ammonia added.
  4. Step 4 — New concentration after refill to 200 L: 128 mg ÷ 200 L = 0.64 mg/L.
  5. Step 5 — Compare to threshold: 0.64 mg/L is still above 0.5 mg/L. A larger exchange or additional biofilter support is needed; document this outcome in your deviation log and remeasure within the four-hour window.
Answer: Expected NH₃-N after a 20% exchange = 0.64 mg/L, still above the 0.5 mg/L threshold. Further corrective action and documentation are required.
4. You are preparing a live Artemia nauplius feed. The protocol calls for 5 nauplii per mL delivered, and your larval tank holds 50 L. You plan to feed at a density of 5 nauplii mL⁻¹ of tank volume. You count your harvest culture under the microscope and find 200 nauplii per mL. How many mL of culture do you need to add to the tank?
  1. Step 1 — Determine total nauplii needed: 5 nauplii per mL × 50,000 mL (50 L) = 250,000 nauplii.
  2. Step 2 — Calculate volume of culture required: 250,000 nauplii ÷ 200 nauplii per mL = 1,250 mL of culture.
  3. Step 3 — Confirm this is a practical volume to add relative to tank size (1,250 mL into 50,000 mL = 2.5% volume addition, which is acceptable). Record culture density, volume delivered, and time in the log.
Answer: Add 1,250 mL (1.25 L) of the Artemia culture to deliver 5 nauplii per mL of tank volume.

The math in this lesson2

Learners compute cohort survival rate from fish counted at day 10 versus stocked.
7.RP.3F-LE.4
Brush up in the math halls at newSchoolWorks.com:
In class: Daily operations rotation: each student independently completes the full morning task list for their assigned tank—water quality sweep, mortality count and removal, feeding, and log entry—within the posted two-hour morning window, without instructor prompting, for ten consecutive weekdays. · Problem response documentation: when any parameter exceeds threshold (as it will, by instructor design at least once), students identify the deviation in their log, list three possible causes, select and implement a corrective action, and record outcome within four hours. · Cohort report presentation: at the end of the run, each student prepares and orally presents a five-minute cohort summary including survival curve, growth data, FCR, notable events, and one recommendation for improving the protocol, to the class and instructor.
Materials: Operational hatchery tank assigned per student, full complement of water quality meters and test kits, live-feed cultures, species-appropriate dry feed, production log (blank), siphon equipment, stereo microscope, cohort report template, presentation materials
Check: Log complete for all 10 days with no missing entries; at least one deviation correctly identified, documented, and corrected with outcome recorded; cohort report contains accurate survival rate, growth rate, and FCR with supporting data — all three requirements must be met to pass.

Practice check8

Answer each question, then check it. Nothing is recorded; this is your own practice.

Hatchery Operations
1. A hatchery technician finishes feeding but forgets to record the ration in the production log until the following morning. Which statement best describes why this practice is problematic?
Water Quality Management
2. You find that dissolved oxygen in your tank has dropped below the posted threshold at 6:00 a.m. According to the deviation response protocol, by what time must you have identified the cause, implemented a corrective action, and recorded the outcome?
Production Metrics
3. A tank is stocked with 400 larvae. After 10 days, 360 animals are alive. What is the survival rate?
Production Metrics
4. A cohort has a mean start weight of 1.0 g and a mean end weight of 2.718 g after 10 days (note: ln(2.718) ≈ 1.000 and ln(1.0) = 0). What is the approximate SGR?
Hatchery Operations
5. When preparing Artemia nauplii for feeding larval fish, why must the nauplii be separated from unhatched cysts and shells before delivery to the tank?
Water Quality Management
6. A technician notices that the pH in a larval tank has risen to 9.1 by mid-afternoon on a sunny day, well above the posted threshold. The most likely cause in an outdoor or greenhouse facility is:
Workplace Safety
7. While energizing a pump at the hatchery, you notice the power cord is lying in a puddle of water. What is the correct immediate action?
Production Metrics
8. Over a 10-day run, a cohort's initial biomass was 800 g and final biomass was 1,200 g. Total dry feed delivered was 240 g. What is the FCR, and how should it be interpreted?
Record this lesson on my transcript. Sign in with your key and enrollment email to record lessons (enroll free if you have no key). This page stays open to read and practise.
← Previous lessonProgram plan