Aquarium Fisheries Research Articles

HIGH MORTALITY DURING SETTLEMENT IS A POPULATION BOTTLENECK FOR A TROPICAL SURGEONFISH

Replenishment of benthic marine populations typically involves “settlement” from pelagic larval to benthic juvenile habitats. Mortality during this transition has been unknown because of the difficulty of measuring propagule supply in open water. For three weeks, we compared the nocturnal passage of presettlement fishes across the barrier reef encircling Moorea Island (French Polynesia) with the abundance of benthic recruits in the back-reef lagoon on the following morning. During this time, >40,000 presettlement unicornfish, Naso unicornis entered our study area of ∼1 km2 with half arriving on just two nights. Using coupled Beverton-Holt functions to describe the decay of each cohort, we were able to predict the daily abundance of recruits and their final age structure from the presettlement inputs. The best model estimated that ∼61% of the potential settlers were lost between their nocturnal arrival and the following morning, independent of cohort size. Postsettlement mortality was density dependent, varying between 9% and 20% per day. We attribute all mortality to predation and suggest that high risk associated with settlement has shaped colonization strategies. Because fishing targets the survivors of this population bottleneck, aquarium fisheries may be more sustainable when sourced from pelagic juveniles.

Evaluating Effectiveness of a Marine Protected Area Network in West Hawai'i to Increase Productivity of an Aquarium Fishery

A network of nine Fish Replenishment Areas (FRAs) was established in West Hawai'i in 2000 in response to declines of reef fishes taken by aquarium collectors. In 1999, we established 23 study sites in FRAs, areas open to collectors, and reference areas (existing protected areas) to collect data both before and after the closure of the FRA network in 2000. To date we have conducted 23 bimonthly fish surveys as well as surveys of the benthic habitats of all sites. Baseline surveys, done before FRA closure, document significant effects of aquarium collector harvesting on selected fishes. On average, aquarium fishes were 26% less abundant in newly established FRAs (formerly open) than in adjacent reference areas. Analysis of postclosure surveys in 2000Ð2002 using a Before-After-Control-Impact procedure provided evidence of a significant increase in two of the 10 species examined, including the yellow tang (Zebrasoma flavescens), the most collected aquarium fish in Hawai'i. The recovery of yellow tangs to preexploitation levels in the FRAs was probably due to the high number of newly recruited fishes observed in 2001Ð2002. Large recruitment events are rare in West Hawai'i but are likely to be an important factor determining the effectiveness of Marine Protected Areas to help replenish depleted fish populations.

Status of Aquarium Fisheries of Rajshahi City

An aquarium is an enclosed body of water containing a mixture of selected and unselected captive living aquatic organism. It is essentially unstable and to obtain stability must be carefully designed and managed (Suxena 2003). Recently aquarium technology means that the technical problems of keening aquatic animals have in principle been solved. It includes about water preparation and the constant monitoring of water quality i.e. pH, hardness, dissolve oxygen, temperature etc. and for this heater, pumps and filter is used. For first time colorful fishes are imported in our country in 1992 and the business was confined in some limited shops of Katabaon area of Dhaka city. But now this business is very common in all over the country (Akhter 1995). It is not only enhancing the beauty of a house but also it is a source of recreation. Japanese can realize the presage of earthquake or can predict about natural disaster by watching the sudden movement of the aquarium fishes (Shafi 1998). Similarly to get rid of mental stress, watching fish is reported well and this also helps to decrease the high blood pressure (Hervert 1999). In Rajshahi city aquarium business started at the last decade and it is spreading rapidly. So development of aquarium fisheries is highly significant here. Â doi: 10.3329/jbs.v15i0.2159 J. bio-sci. 15: 169-171, 2007