Juvenile Bonefish Habitats

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Background

While it may seem self-evident that healthy habitats are essential for healthy fisheries, in many cases habitat is not part of fisheries management plans. One of the challenges to including habitat in fisheries management plans is that habitat use by many species is not known. This is the case for bonefish, Albula vulpes, whose habitat use patterns are not sufficiently documented for effective conservaton. Because the juvenile life stage is the most susceptible to harm from habitat loss and degradation, of particular concern is identifying juvenile bonefish habitats.

Although overfishing is most often listed as causing declines of fish populations, loss and degradation of habitats is at least as important. This is especially true for fisheries that are primarily catch and release, such as bonefish. Habitats essential to supporting juvenile fishes are called nurseries. If juvenile fish don’t have habitats where they can grow and be protected from predators, then not enough juveniles will survive to adulthood, and the fishery will decline. Nurseries are especially susceptible to habitat degradation because they tend to occur in shallow, coastal areas that are impacted by human activities.

Potential loss of nursery habitats is especially troubling because the impacts of this habitat loss may not be felt for many years. This is especially true for long-lived species like bonefish, which can live 20 years or more. As long-lived species age, their growth rate slows and fish of a wide age range may be of similar size. Thus, it is difficult to determine the age structure of the population – are there enough young fish to replace the aging fish each year? In a worst case scenario, if very few juveniles are surviving each year, the population decline won’t be seen until the older fish begin to die off without being replaced by enough juveniles. This means that
by the time the problem is realized, it may be years too late. Since juvenile bonefish habitats remain unknown, and the potential negative impacts to the bonefish population are large, it is important to determine what type of habitats are required by juvenile bonefish. Once juvenile bonefish habitat types are identified, future research can address how widespread these juvenile habitats are, and the extent that juveniles are surviving to adulthood.

Ongoing Research

During previous work in the Florida Keys, South Florida, Southwest Florida, and Belize, more than 1,000 juvenile bonefish were captured along sandy beaches. However, more than 95% of these juveniles were genetically identified as Albula garcia, a bonefish species that looks like Albula vulpes, but constitutes less than 4% of the recreational fishery. In other words, we found juvenile bonefish, but not the species that supports the fishery. In addition to sandy beaches, we also sampled mangrove shorelines, seagrass beds, and rocky shorelines, and caught very few juvenile bonefish. The information collected thus far is pointing toward open sandy areas greater than four feet in depth as the likely habitat for juvenile Albula vulpes. If you find juvenile bonefish less than 6" long (not on sandy beaches), please let us know.

BTT is currently supporting research in The Bahamas to identify juvenile bonefish habitats. Since the bonefish population in The Bahamas is so large, BTT has refocused here because more fish should increase the likelihood of finding juveniles. Thus far, results are pointing to deeper sandy bottoms, as previous work suggested, as the primary juvenile Albula vulpes habitat.  Once juvenile bonefish habitat is identified, efforts will turn toward habitat conservation.