Considering the scenarios presented about the milkfish population, does the carrying capacity has a big role in limiting its population size? Why or why not?
Milkfish (Chanos chanos) is the only fish species that belongs to Family Chanidae which is nearly related to tuna and salmon due to its fusiform shape and migratory nature (FAO 2009; BFAR 2020). It is widely distributed in the Indo-pacific region and abundantly collected in the South and Southeast Asian, and West Pacific Regions (BFAR 2010). Milkfish is one of the most commercially important fish species in the Philippines (Samson 1984).
Milkfish reach sexual maturity (approximately 1.5m length and 20 kg weight) in five years in large floating cages, but may take 8-10 years in ponds and concrete tanks (FAO 2009). In the natural environment, milkfish populations near the coral reefs spawn during warm months of the year while populations near the equator spawn year-round. First-time spawners produce fewer eggs but larger and older broodstocks produce as many eggs as wild adults of similar size. Broodstocks of about 8 years old and about 6 kg produce 3-4 million eggs. Juvenile and adults milkfish eat a wide variety of relatively soft and small food items such as microbial mats, detritus, epiphytes, and zooplankton.
Milkfish can be grown in ponds, pens, or cages (FAO 2009). Stocking density is an important parameter to be considered to maximize production because relatively less number of fish in a pond, pen, or cage could get more space, food, and dissolved oxygen (Hasan et al. 2010). In the Philippines, most ponds employ extensive and semi-intensive stocking densities (50 000 – 100000/ha) with large shallow pond units, tidal water exchange, natural food, and with minimal use of fertilizer. Taiwan, on the other hand, employs intensive stocking densities (150 000-200 000/ha).
Fish pen in lake waters have 30 000-35 000/ha stocking density with provision of supplemental commercial diets. Cage farming which is commonly carried out along coastal bays, stocking rates are quite high, from 5 up to 30/m3.
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1. Considering the scenarios presented about the milkfish population, does the
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